Increased micronuclei and bulky DNA adducts in cord blood after maternal exposures to traffic-related air pollution

Role of Oxidative Stress and DNA Damage on Preterm Birth Outcome

Background: Preterm birth (PTB) poses a significant global health challenge and focused research is vital for improving maternal and neonatal health outcomes. The purpose of this study was to determine the effect of oxidative stress (OS) and DNA damage on PTB. Methods: There were two groups: (a) cases consisting of mothers with PTB (<37 weeks of gestation, n = 100) and (b) controls consisting of mothers with term birth (>37 weeks of gestation, n = 100). Women with vaginal infection, non-cephalic presentation, multiple gestations, fetal anomalies, Cesarean delivery, pregnancy with Mullerian anomalies, or preeclampsia were excluded from the study. OS analysis was conducted by measuring levels of superoxide dismutase (SOD), catalase (CAT), lipid peroxidation (LPO), and total protein and DNA damage were evaluated by CBMN-Cyt assay. Statistical analysis was performed using students' t-test and one-way ANOVA. Results: Low levels of antioxidants SOD and CAT (p < .0001), and total protein (p < .0001), besides high malondialdehyde (byproduct of LPO) (p < .0001) were observed in the PTB group. Moreover, high frequencies of micronuclei (p < .0001) and nucleoplasmic buds (p < .01) were detected in the PTB mothers compared to term birth mothers, while no significance was observed in the nucleoplasmic bridge frequencies. Conclusion: When the body's immune system and antioxidants fail to cope up with the generated OS, it can lead to PTB. Along with other body tests, OS markers and CBMN-Cyt tests have the potential to be used in diagnostics for early warning as well as monitoring and advising mothers for a better pregnancy outcome.

Prenatal exposure to ambient air pollutants and congenital heart defects: An umbrella review

BACKGROUND

Prenatal exposure to ambient air pollutants has been linked to congenital heart defects (CHD), but findings of existing systematic reviews have been mixed.

OBJECTIVE

To assess the epidemiological evidence on associations between prenatal exposure to ambient air pollutants and CHD subtypes, based on a systematic overview of reviews ("umbrella review").

METHODS

We conducted a systematic search for reviews assessing associations between prenatal exposure to criteria air pollutants and CHD. The risk of bias was evaluated using the Risk of Bias in Systematic Reviews (ROBIS) tool. The certainty of the systematic review findings was graded using the Navigation Guide methodology.

RESULTS

We identified eleven systematic reviews, including eight with meta-analyses, assessing in total 35 primary studies of prenatal exposure to criteria air pollutants and various CHD subtypes. The certainty of the findings of four meta-analyses indicating an increased risk for coarctation of the aorta associated with nitrogen dioxide exposure was rated as moderate. The certainty of findings indicating positive, inverse, or null associations for other pollutant-subtype combinations was rated as very low to low, based on low precision and high statistical heterogeneity of summary odds ratios (SOR), substantial inconsistencies between review findings, and methodological limitations of the systematic reviews.

DISCUSSION

The inconsistent findings and high statistical heterogeneity of many SOR of the included systematic reviews may partly be traced to differences in methodological approaches, and the risk of bias across included reviews (e.g., inclusion criteria, systematic search strategies, synthesis methods) and primary studies (e.g., exposure assessment, diagnostic criteria). Adherence to appropriate systematic review guidelines for environmental health research, as well as rigorous evaluation of risk of bias in primary studies, are essential for future risk assessments and policy-making. Still, our findings suggest that prenatal exposure to ambient air pollutants may increase risks for at least some CHD subtypes.

Traffic-Related Air Pollution and Ground-Level Ozone Associated Global DNA Hypomethylation and Bulky DNA Adduct Formation

Studies have indicated that air pollution, including surface-level ozone (O₃), can significantly influence the risk of chronic diseases. To better understand the carcinogenic mechanisms of air pollutants and identify predictive disease biomarkers, we examined the association between traffic-related pollutants with DNA methylation alterations and bulky DNA adducts, two biomarkers of carcinogen exposure and cancer risk, in the peripheral blood of 140 volunteers-95 traffic police officers, and 45 unexposed subjects. The DNA methylation and adduct measurements were performed by bisulfite-PCR and pyrosequencing and ³²P-postlabeling assay. Airborne levels of benzo(a)pyrene [B(a)P], carbon monoxide, and tropospheric O₃ were determined by personal exposure biomonitoring or by fixed monitoring stations. Overall, air pollution exposure was associated with a significant reduction (1.41 units) in global DNA methylation (95% C.I. -2.65-0.04, p = 0.026). The decrement in ALU repetitive elements was greatest in the policemen working downtown (95% C.I. -3.23--0.49, p = 0.008). The DNA adducts were found to be significantly increased (0.45 units) in the municipal officers with respect to unexposed subjects (95% C.I. 0.02-0.88, p = 0.039), mainly in those who were controlling traffic in downtown areas (95% C.I. 0.39-1.29, p < 0.001). Regression models indicated an increment of ALU methylation at higher B(a)P concentrations (95% C.I. 0.03-0.60, p = 0.032). Moreover, statistical models showed a decrement in ALU methylation and an increment of DNA damage only above the cut-off value of 30 µg/m³ O₃. A significant increment of 0.73 units of IL-6 gene methylation was also found in smokers with respect to non-smokers. Our results highlighted the role of air pollution on epigenetic alterations and genotoxic effects, especially above the target value of 30 µg/m³ surface-level O₃, supporting the necessity for developing public health strategies aimed to reduce traffic-related air pollution molecular alterations.

Associating Air Pollution with Cytokinesis-Block Micronucleus Assay Parameters in Lymphocytes of the General Population in Zagreb (Croatia)

Air pollution is recognized as one of the most serious public health issues worldwide and was declared to be a leading environmental cause of cancer deaths. At the same time, the cytokinesis-block micronucleus (CBMN) assay serves as a cancer predictive method that is extensively used in human biomonitoring for populations exposed to environmental contamination. The objective of this cross-sectional study is two-fold: to evaluate genomic instability in a sample (N = 130) of healthy, general population residents from Zagreb (Croatia), chronically exposed to different levels of air pollution, and to relate them to air pollution levels in the period from 2011 to 2015. Measured frequencies of CBMN assay parameters were in agreement with the baseline data for the general population of Croatia. Air pollution exposure was based on four factors obtained from a factor analysis of all exposure data obtained for the examined period. Based on the statistical results, we did not observe a significant positive association between any of the CBMN assay parameters tested and measured air pollution parameters for designated time windows, except for benzo(a)pyrene (B[a]P) that showed significant negative association. Our results show that measured air pollution parameters are largely below the regulatory limits, except for B[a]P, and as such, they do not affect CBMN assay parameters’ frequency. Nevertheless, as air pollution is identified as a major health threat, it is necessary to conduct prospective studies investigating the effect of air pollution on genome integrity and human health.

A perspective on persistent toxicants in veterans and amyotrophic lateral sclerosis: identifying exposures determining higher ALS risk

Multiple studies indicate that United States veterans have an increased risk of developing amyotrophic lateral sclerosis (ALS) compared to civilians. However, the responsible etiological factors are unknown. In the general population, specific occupational (e.g. truck drivers, airline pilots) and environmental exposures (e.g. metals, pesticides) are associated with an increased ALS risk. As such, the increased prevalence of ALS in veterans strongly suggests that there are exposures experienced by military personnel that are disproportionate to civilians. During service, veterans may encounter numerous neurotoxic exposures (e.g. burn pits, engine exhaust, firing ranges). So far, however, there is a paucity of studies investigating environmental factors contributing to ALS in veterans and even fewer assessing their exposure using biomarkers. Herein, we discuss ALS pathogenesis in relation to a series of persistent neurotoxicants (often emitted as mixtures) including: chemical elements, nanoparticles and lipophilic toxicants such as dioxins, polycyclic aromatic hydrocarbons and polychlorinated biphenyls. We propose these toxicants should be directly measured in veteran central nervous system tissue, where they may have accumulated for decades. Specific toxicants (or mixtures thereof) may accelerate ALS development following a multistep hypothesis or act synergistically with other service-linked exposures (e.g. head trauma/concussions). Such possibilities could explain the lower age of onset observed in veterans compared to civilians. Identifying high-risk exposures within vulnerable populations is key to understanding ALS etiopathogenesis and is urgently needed to act upon modifiable risk factors for military personnel who deserve enhanced protection during their years of service, not only for their short-term, but also long-term health.

Prenatal exposure to ambient air pollutants and early infant growth and adiposity in the Southern California Mother's Milk Study

BACKGROUND

Prior epidemiological and animal work has linked in utero exposure to ambient air pollutants (AAP) with accelerated postnatal weight gain, which is predictive of increased cardiometabolic risk factors in childhood and adolescence. However, few studies have assessed changes in infant body composition or multiple pollutant exposures. Therefore, the objective of this study was to examine relationships between prenatal residential AAP exposure with infant growth and adiposity.

METHODS

Residential exposure to AAP (particulate matter < 2.5 and 10 microns in aerodynamic diameter [PM2.5, PM10]; nitrogen dioxide [NO2]; ozone [O3]; oxidative capacity [Oxwt: redox-weighted oxidative potential of O3 and NO2]) was modeled by spatial interpolation of monitoring stations via an inverse distance-squared weighting (IDW2) algorithm for 123 participants from the longitudinal Mother's Milk Study, an ongoing cohort of Hispanic mother-infant dyads from Southern California. Outcomes included changes in infant growth (weight, length), total subcutaneous fat (TSF; calculated via infant skinfold thickness measures) and fat distribution (umbilical circumference, central to total subcutaneous fat [CTSF]) and were calculated by subtracting 1-month measures from 6-month measures. Multivariable linear regression was performed to examine relationships between prenatal AAP exposure and infant outcomes. Models adjusted for maternal age, pre-pregnancy body mass index, socioeconomic status, infant age, sex, and breastfeeding frequency. Sex interactions were tested, and effects are reported for each standard deviation increase in exposure.

RESULTS

NO2 was associated with greater infant weight gain (β = 0.14, p = 0.02) and TSF (β = 1.69, p = 0.02). PM10 and PM2.5 were associated with change in umbilical circumference (β = 0.73, p = 0.003) and TSF (β = 1.53, p = 0.04), respectively. Associations of Oxwt (pinteractions < 0.10) with infant length change, umbilical circumference, and CTSF were modified by infant sex. Oxwt was associated with attenuated infant length change among males (β = -0.60, p = 0.01), but not females (β = 0.16, p = 0.49); umbilical circumference among females (β = 0.92, p = 0.009), but not males (β = -0.00, p = 0.99); and CTSF among males (β = 0.01, p = 0.03), but not females (β = 0.00, p = 0.51).

CONCLUSION

Prenatal AAP exposure was associated with increased weight gain and anthropometric measures from 1-to-6 months of life among Hispanic infants. Sex-specific associations suggest differential consequences of in utero oxidative stress. These results indicate that prenatal AAP exposure may alter infant growth, which has potential to increase childhood obesity risk.

Micronuclei, reproduction and child health

The current review looks for relationships between results from biomarker studies with micronucleus and health effects related to reproduction and children. In adults, an age related increase in MN is well known as well as associations with environmental exposures especially air pollution from traffic and smoking. Literature searches in PubMED and SCOPUS were performed with the following keywords reproduction, children, micronuclei, health effects. In total 162 studies were identified with the keyword children. Concerning children and health and children and environmental exposures, the titles and abstracts of a total of 162 publications were screened for language, inclusion of data from children and selected according to a study selection chart. 9 studies were included for children and health, and 21 studies for children and environmental exposures, with 12 in buccal cells and 9 in lymphocytes. The publications were read and included in tables if data on controls was available. MN frequencies were collected for peripheral blood lymphocytes (PBLs), reticulocytes or buccal cells (BC) and reported as Mean ± SD or Median (IQR). The Mean frequency Ratio, MRi, corresponding to the MN mean for study persons divided by MN mean for control persons was stated as reported in the publication or calculated by us from the data in the publication, where possible. Our systematic analysis revealed a number of positive associations of MN frequencies as a marker of increased health risk in relation to reproduction as well as child health. The majority of studies reported with children concerns exposures of children as well as maternal exposures and newborn health with MN as a biomarker of exposure. Exposure monitoring by MN as biomarker is also reported in studies of school children however most often not related to health effects. The MRis are found in ranges from 1 to 5.5 most studies around 2. As far as MN frequencies in children and exposure are concerned, the MRis range from 0.9 to 5.5, with a range from 1.3-4.9 for lymphocytes and from 1.5 to 2.5 in buccal cells, except for two studies with no differences found between cases and controls. Only one study is available for MRi calculation in reticulocytes with the value of 2.3. These data are supporting MN as a relevant biomarker for children health. However, the data is mostly from small studies with different protocol leaving out the possibility of metanalyses and even statistical comparisons among studies. The actual risk from elevated MNs in children waits large cohort studies with pooled datasets as performed with MN measured in adults. Introduction of buccal cells as non invasive alternative to lymphocytes is increasing and as with the lymphocytes standardised protocols are recommended to enable comparative studies and metaanalyses.

Maternal air pollution exposure and congenital heart defects in offspring: A systematic review and meta-analysis

BACKGROUND

Congenital heart defects (CHDs) has a multifactorial causation with a strong genetic component and many environmental triggers. Emerging body of empirical studies suggest that air pollution is an important contributor to the development of CHDs, however, there still remains some controversy over the current evidence, and to the authors' knowledge, no studies have reviewed the most recent evidence.

OBJECTIVES

We performed a systematic review and meta-analysis of epidemiological literature to investigate the relationship between maternal air pollution exposure and CHDs risk in offspring. The presence of heterogeneity and publication bias across available studies were also examined.

METHODS

An extensive literature search of epidemiological studies pertaining to air pollution and CHDs, published in English language, until August 1, 2019 was conducted. Summary risk estimates of pollution-outcome combinations were calculated for i) risk per specific increment of concentration and ii) risk at high versus low exposure level in each study using fixed-effect model or random-effects model.

RESULTS

A total of 26 studies were finally included. In the meta-analyses, high versus low carbon monoxide (CO) exposure was associated with an increased risk of tetralogy of Fallot [odds ratio (OR) = 1.21, 95% confidence interval (CI): 1.04-1.41], yet particulate matter ≤ 5 μm (PM_2.5) exposure was marginally associated with it. Increased risk of atrial septal defects (ASDs) was found for each 10 μg/m³ and 10 ppb increment in particulate matter ≤ 10 μm (PM₁₀) and ozone (O₃) exposure, respectively (OR = 1.04, 95% CI: 1.00-1.09; OR = 1.09, 95% CI: 1.02-1.17). Categorical nitrogen dioxide (NO₂) exposure was associated with an increased risk of coarctation of the aorta (OR for high versus low = 1.14, 95% CI: 1.02-1.26). Analyses for other combinations yielded none statistically significant associations. Sensitive analyses showed similar findings.

CONCLUSIONS

The summary effect estimates from this study suggest statistically significant associations between increased risk of specific CHDs subtypes and PM_2.5, PM₁₀, NO₂, CO, and O₃ exposures. Further studies, especially conducted in developing countries, with improvements in exposure assessing, outcome harmonizing, and mechanistic understanding are needed to elaborate the suggestive associations.

Solid fuel use for heating and risks of breast and cervical cancer mortality in China

BACKGROUND

Carcinogens released from indoor burning of solid fuels are believed to enter the bloodstream and to be metabolized in breast and cervical tissues. Little evidence exists about the relationship of solid fuel use from heating with breast and cervical cancer.

OBJECTIVES

To examine the association of solid heating fuel use with breast and cervical cancer mortality.

METHODS

This study included female participants aged 30-79 years who were enrolled in the China Kadoorie Biobank during 2004-2008 from 10 diverse regions across China. During a 10.2-year median follow-up, 177 breast cancer deaths and 113 cervical cancer deaths were documented. Multivariable Cox regression models yielded adjusted hazard ratios (HRs) for the associations of self-reported long-term heating fuel exposure with two cancer deaths. Stratified analyses were used to assess effect modification.

RESULTS

We included 236,116 participants for breast cancer analyses and 228,795 for cervical cancer analyses. Compared with non-solid fuel use, the fully adjusted HRs of cervical cancer deaths were 1.75 (0.91-3.38) for wood use, 2.23 (1.09-4.59) for mixed fuel (coal and wood) use. No evident relationship was observed for breast cancer deaths. Cervical cancer risk increased with the duration of solid fuel use (P for trend = 0.041). Elevated cervical cancer risk was observed in post-menopausal women (HR 2.01, 1.01-4.03), not in pre-menopausal women (HR 0.77, 0.56-2.31) (P for heterogeneity = 0.004); and in those aged ≥50 years (HR 2.56, 1.17-5.86), not in those aged < 50 years (HR 0.69, 0.26-1.84) (P < 0.001).

CONCLUSION

Indoor solid fuel combustion for heating may be associated with a higher risk for cervical cancer death, but not for breast cancer. The strength of the association increased with the duration of exposure and was modified by age and menopause status.

Effects of prenatal exposure to NO2 on children's neurodevelopment: a systematic review and meta-analysis

The neurotoxicity of NO₂ exposure is well-known and potentially causes impaired of neural functions. This review aimed to estimate associations between prenatal NO₂ exposure and neurodevelopment for children. Articles published until May 2019 reported prenatal NO₂ exposure and children's cognition, psychomotor, language, attention, IQ, and behavior function were searched according to all related terms. The main databases we retrieved included PubMed, Web of Science, Embase, and Cochrane Library. Coefficient was extracted, conversed, and synthesized by random effects meta-analysis. Meanwhile, qualitatively describe would be used for some studies which cannot be synthesized quantitatively for lack of quantity or methods inconsistency. Finally, a total of 3848 citations were searched, and only 10 studies were included. We estimated that per 10 μg/m³ increase of NO₂ during pregnancy was associated with a - 0.76 point decrease in global psychomotor (95% CI, - 1.34, - 0.18) and a - 0.62 point decrease in fine psychomotor for children (95% CI, - 1.09, - 0.16). But no significant association found in general cognitive and language. In addition, through the literature review, it seemed that prenatal exposure to NO₂ might cause adverse impacts on children's attention, IQ, and different behaviors, but this requires confirmation from further researches. Our study indicated that prenatal exposure to NO₂ seems to be associated with impaired neural development for children, especially for fine psychomotor. However, further studies are needed for determining the effects of prenatal air pollution exposure on attention, IQ, and behavior.

Children's microvascular traits and ambient air pollution exposure during pregnancy and early childhood: prospective evidence to elucidate the developmental origin of particle-induced disease

BACKGROUND

Particulate matter exposure during in utero life may entail adverse health outcomes later in life. The microvasculature undergoes extensive, organ-specific prenatal maturation. A growing body of evidence shows that cardiovascular disease in adulthood is rooted in a dysfunctional fetal and perinatal development, in particular that of the microcirculation. We investigate whether prenatal or postnatal exposure to PM_2.5 (particulate matter with a diameter ≤ 2.5 μm) or NO₂ is related to microvascular traits in children between the age of four and six.

METHODS

We measured the retinal microvascular diameters, the central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE), and the vessel curvature by means of the tortuosity index (TI) in young children (mean [SD] age 4.6 [0.4] years), followed longitudinally within the ENVIRONAGE birth cohort. We modeled daily prenatal and postnatal PM_2.5 and NO₂ exposure levels for each participant's home address using a high-resolution spatiotemporal model.

RESULTS

An interquartile range (IQR) increase in PM_2.5 exposure during the entire pregnancy was associated with a 3.85-μm (95% CI, 0.10 to 7.60; p = 0.04) widening of the CRVE and a 2.87-μm (95% CI, 0.12 to 5.62; p = 0.04) widening of the CRAE. For prenatal NO₂ exposure, an IQR increase was found to widen the CRVE with 4.03 μm (95% CI, 0.44 to 7.63; p = 0.03) and the CRAE with 2.92 μm (95% CI, 0.29 to 5.56; p = 0.03). Furthermore, a higher TI score was associated with higher prenatal NO₂ exposure. We observed a postnatal effect of short-term PM_2.5 exposure on the CRAE and a childhood NO₂ exposure effect on both the CRVE and CRAE.

CONCLUSIONS

Our results link prenatal and postnatal air pollution exposure with changes in a child's microvascular traits as a fundamental novel mechanism to explain the developmental origin of cardiovascular disease.

The Impact of Mother's Living Environment Exposure on Genome Damage, Immunological Status, and Sex Hormone Levels in Newborns

Background: The aim of this study was to compare for the first time IL-6 (Interleukin 6), testosterone (T) and estradiol (E) levels, their ratio (E/T), micronucleus (MN), and nuclear bridge (NB) frequency between newborns with regard to their mother’s residency and diet. Our results should enable an assessment of the possible environmental endocrine effects and interaction between biomarkers, pointing to possible associated health risks. Methods: Fifty full-term newborns of both sexes, whose mothers were healthy and not occupationally exposed to any known carcinogen, were analyzed. All of the mothers filled in a detailed questionnaire. Results: The results showed significantly higher levels of E in newborns of mothers with agricultural residency than those born by mothers with urban residency. Significantly, lower levels of E were measured in newborns of mothers who drank milk and carbonated beverages more frequently. Testosterone was significantly higher in boys of mothers with agricultural residency than from mothers with urban residency. Residence and other parameters had no impact on the difference in MN frequency. IL-6 levels were higher in newborns of mothers with agricultural residency. NB levels were significantly associated with E. A significant association between E levels and IL-6 was found. Conclusion: Our results were the first to show a significant impact of the mother’s agricultural residency and diet on their newborns’ sex hormone and IL-6 levels and their association.

Micronuclei and disease - Report of HUMN project workshop at Rennes 2019 EEMGS conference

The "Micronuclei and Disease" workshop was organized by the HUMN Project consortium and hosted by the European Environmental Mutagen and Genomics Society at their annual meeting in Rennes, France, on 23 May 2019. The program of the workshop focused on addressing the emerging evidence linking micronucleus (MN) frequency to human disease. The first objective was to review what has been published and evaluate the level and quality of evidence for the connection between MN frequency and various diseases through all life stages. The second objective was to identify the knowledge gaps and what else needs to be done to determine the clinical utility of MN assays as predictors of disease risk and of prognosis when disease is active. Speakers at the workshop discussed the association of MN frequency with inflammation, infertility, pregnancy complications, obesity, diabetes, cardiovascular disease, kidney disease, cervical and bladder cancer, oral head and neck cancer, lung cancer, accelerated ageing syndromes, neurodegenerative diseases, and a road-map on how to utilise this knowledge was proposed. The outcomes of the workshop indicated that there are significant opportunities for translating the application of MN assays into clinical practice to improve disease prevention and risk management and to inform public health policy.

Daily cooking duration and its joint effects with genetic polymorphisms on lung cancer incidence: Results from a Chinese prospective cohort study

OBJECTIVES

In this study, we conducted a prospective cohort study to investigate the joint effects of daily cooking duration with single nucleotide polymorphisms (SNPs) on lung cancer incidence.

MATERIALS AND METHODS

A total of 33,868 individuals recruited in 2013 from Dongfeng-Tongji cohort study were included in our research, in which 5178 participants were genotyped. Daily cooking duration was accessed by questionnaire, and the incident lung cancer cases were confirmed. Fifteen lung cancer related SNPs were selected according to the previous reports. We used the multiple Cox regression models to evaluate the separate and joint effects of daily cooking duration and SNPs on lung cancer incidence.

RESULTS

Each 1-h increase in daily cooking duration was associated with a 17% elevated risk of lung cancer incidence [hazard ratio (HR) (95%CI) = 1.17(1.03, 1.33)]. Specifically, subjects with daily cooking duration >2 h/day had a 2.05-fold increased incident risk of lung cancer than those without cooking [HR(95%CI) = 2.05(1.20, 3.53)] (P_trend = 0.011). The rs2395185 and rs3817963, both located at 6p21.32, were significantly associated with lung cancer incidence. Compared with no cooking subjects with rs2395185GG or rs3817963TT genotype, subjects with daily cooking >2 h/day and carrying rs2395185GT + TT genotypes had a 2.48-fold increased risk of lung cancer [HR(95%CI) = 2.48(1.03, 5.97)], and there were significant joint effects of rs3817963TC + CC with daily cooking 1-2 and >2 h/day [HR(95%CI) = 2.23(1.07, 4.64) and 2.22(1.05, 4.68), respectively].

CONCLUSIONS

Longer daily cooking duration, especially daily cooking >2 h/day, was associated with increased risk of lung cancer. There were significant joint effects of rs2395185 and rs3817963 with daily cooking duration on lung cancer incidence. This study offered a new indicator of cooking related pollution exposure and added new evidence for the joint effects of environment and genetic factors on lung cancer incidence.

Environmental exposures during windows of susceptibility for breast cancer: a framework for prevention research

Background

The long time from exposure to potentially harmful chemicals until breast cancer occurrence poses challenges for designing etiologic studies and for implementing successful prevention programs. Growing evidence from animal and human studies indicates that distinct time periods of heightened susceptibility to endocrine disruptors exist throughout the life course. The influence of environmental chemicals on breast cancer risk may be greater during several windows of susceptibility (WOS) in a woman’s life, including prenatal development, puberty, pregnancy, and the menopausal transition. These time windows are considered as specific periods of susceptibility for breast cancer because significant structural and functional changes occur in the mammary gland, as well as alterations in the mammary micro-environment and hormone signaling that may influence risk. Breast cancer research focused on these breast cancer WOS will accelerate understanding of disease etiology and prevention.

Main text

Despite the plausible heightened mechanistic influences of environmental chemicals on breast cancer risk during time periods of change in the mammary gland’s structure and function, most human studies of environmental chemicals are not focused on specific WOS. This article reviews studies conducted over the past few decades that have specifically addressed the effect of environmental chemicals and metals on breast cancer risk during at least one of these WOS. In addition to summarizing the broader evidence-base specific to WOS, we include discussion of the NIH-funded Breast Cancer and the Environment Research Program (BCERP) which included population-based and basic science research focused on specific WOS to evaluate associations between breast cancer risk and particular classes of endocrine-disrupting chemicals—including polycyclic aromatic hydrocarbons, perfluorinated compounds, polybrominated diphenyl ethers, and phenols—and metals. We outline ways in which ongoing transdisciplinary BCERP projects incorporate animal research and human epidemiologic studies in close partnership with community organizations and communication scientists to identify research priorities and effectively translate evidence-based findings to the public and policy makers.

Conclusions

An integrative model of breast cancer research is needed to determine the impact and mechanisms of action of endocrine disruptors at different WOS. By focusing on environmental chemical exposure during specific WOS, scientists and their community partners may identify when prevention efforts are likely to be most effective.

Particulate matter-associated micronuclei frequencies in maternal and cord blood lymphocytes

Studies associate particulate matter (PM) exposure with pulmonary, cardiovascular, and neurologic diseases. Elevated levels of coarse (PM10) and fine (PM2.5) PM have been reported in the Mexico City metropolitan area during the last two decades. There is limited information if these conditions affect newborns. We associated maternal exposure to PM reported by the monitoring stations considering the place of residence of each participant with the presence of genotoxic damage (cytome analysis) in maternal and umbilical cord blood (UCB) lymphocytes. Eighty-four healthy women in their last quarter of pregnancy met the inclusion criteria. Each volunteer exposure was estimated according to the average PM2.5 and PM10 levels during the last month of gestation. The micronuclei (MN) frequencies in UCB lymphocyte cultures ranged between 0 and 9. They also showed lower cell proliferation indexes than their mothers. There was a strong correlation between the maternal and the UCB MN frequency (ρ = 0.3767, P = 0.0002). Multiple regression analysis including PM10 and PM2.5 levels, maternal age, and occupation, showed a significant and positive association between UCB MN frequency and PM2.5. A statistically significant increase in the MN frequency in both maternal and UCB lymphocytes was observed in samples obtained during the dry season (higher PM levels) as compared with the MN frequency in blood samples obtained during the rainy season (lower PM levels). These results suggest that PM, mainly PM_2.5 , can cross the placenta causing DNA damage in fetal cells which may increase the potential for diseases during childhood or adult life. Environ. Mol. Mutagen. 60:421-427, 2019. © 2019 Wiley Periodicals, Inc.

Transplacental exposure to carcinogens and risks to children: evidence from biomarker studies and the utility of omic profiling

The factors underlying the increasing rates and the geographic variation of childhood cancers are largely unknown. Epidemiological studies provide limited evidence for a possible role in the etiology of certain types of childhood cancer of the exposure of pregnant women to environmental carcinogens (e.g., tobacco smoke and pesticides); however, such evidence is inadequate to allow definitive conclusions. Complementary evidence can be obtained from biomarker-based population studies. Such studies have demonstrated that, following exposure of pregnant mothers, most environmental carcinogens reach the fetus and, in many cases, induce therein genotoxic damage which in adults is known to be associated with increased cancer risk, implying that environmental carcinogens may contribute to the etiology of childhood cancer. During recent years, intermediate disease biomarkers, obtained via omic profiling, have provided additional insights into the impact of transplacental exposures on fetal tissues which, in some cases, are also compatible with a precarcinogenic role of certain in utero exposures. Here we review the epidemiological and biomarker evidence and discuss how further research, especially utilizing high-density profiling, may allow a better evaluation of the links between in utero environmental exposures and cancer in children.

Air pollution and the fetal origin of disease: A systematic review of the molecular signatures of air pollution exposure in human placenta

BACKGROUND

Fetal development is a crucial window of susceptibility in which exposure-related alterations can be induced on the molecular level, leading to potential changes in metabolism and development. The placenta serves as a gatekeeper between mother and fetus, and is in contact with environmental stressors throughout pregnancy. This makes the placenta as a temporary organ an informative non-invasive matrix suitable to investigate omics-related aberrations in association with in utero exposures such as ambient air pollution.

OBJECTIVES

To summarize and discuss the current evidence and define the gaps of knowledge concerning human placental -omics markers in association with prenatal exposure to ambient air pollution.

METHODS

Two investigators independently searched the PubMed, ScienceDirect, and Scopus databases to identify all studies published until January 2017 with an emphasis on epidemiological research on prenatal exposure to ambient air pollution and the effect on placental -omics signatures.

RESULTS

From the initial 386 articles, 25 were retained following an a priori set inclusion and exclusion criteria. We identified eleven studies on the genome, two on the transcriptome, five on the epigenome, five on the proteome category, one study with both genomic and proteomic topics, and one study with both genomic and transcriptomic topics. Six studies discussed the triple relationship between exposure to air pollution during pregnancy, the associated placental -omics marker(s), and the potential effect on disease development later in life. So far, no metabolomic or exposomic data discussing associations between the placenta and prenatal exposure to air pollution have been published.

CONCLUSIONS

Integration of placental biomarkers in an environmental epidemiological context enables researchers to address fundamental questions essential in unraveling the fetal origin of disease and helps to better define the pregnancy exposome of air pollution.

Placental hypoxia-regulating network in relation to birth weight and ponderal index: the ENVIRONAGE Birth Cohort Study

BACKGROUND

HIF1α, miR-210 and its downstream targets ISCU, COX-10, RAD52 and PTEN are all part of the placental hypoxia-responsive network. Tight regulation of this network is required to prevent development of maternal-fetal complications such as fetal growth restriction. HIF1α expression is increased in preeclamptic placentae, but little is known about its association with birth weight in normal pregnancies.

METHODS

We measured placental levels of HIF1α, miR-20a, miR-210, ISCU, COX-10, RAD52 and PTEN in 206 mother-newborn pairs of the ENVIRONAGE birth cohort.

RESULTS

Placental HIF1α gene expression was inversely associated with the ponderal index (PI): for a doubling in placental HIF1α expression, PI decreased by 6.7% (95% confidence interval [CI] 1.3 to 12.0%, p = 0.01). Placental RAD52 expression also displayed an inverse association with PI, a doubling in gene expression was associated with a 6.2% (CI 0.2 to 12.1% p = 0.04) decrease in PI. As for birth weight, we observed a significant association with placental miR-20a expression only in boys, where a doubling in miR-20a expression is associated with a 54.2 g (CI 0.6 to 108 g, p = 0.05) increase in birth weight.

CONCLUSIONS

The decrease in fetal growth associated with expression of hypoxia-network members HIF1a, RAD52 and miR-20a indicates that this network is important in potential intrauterine insults.

Exposure to air pollution and noise from road traffic and risk of congenital anomalies in the Danish National Birth Cohort

BACKGROUND

Ambient air pollution has been associated with certain congenital anomalies, but few studies rely on assessment of fine-scale variation in air quality and associations with noise from road traffic are unexplored.

METHODS

Among 84,218 liveborn singletons (1997-2002) from the Danish National Birth Cohort with complete covariate data and residential address history from conception until birth, we identified major congenital anomalies in 4018 children. Nitrogen dioxide (NO₂) and noise from road traffic (L_den) burden during fetal life was modeled. Outcome and covariate data were derived from registries, hospital records and questionnaires. Odds ratios (ORs) for eleven major anomaly groups associated with road traffic pollution during first trimester were estimated using logistic regression with generalized estimating equation (GEE) approach.

RESULTS

Most of the associations tested did not suggest increased risks. A 10-µg/m³ increase in NO₂ exposure during first trimester was associated with an adjusted ORs of 1.22 (95% confidence interval: 0.98-1.52) for ear, face and neck anomalies; 1.14 0.98-1.33) for urinary anomalies. A 10-dB increase in road traffic noise was also associated with these subgroups of anomalies as well as with an increased OR for orofacial cleft anomalies (1.17, 0.94-1.47). Inverse associations for several both air pollution and noise were observed for atrial septal defects (0.85, 0.68-1.04 and 0.81, 0.65-0.99, respectively).

CONCLUSIONS

Residential road traffic exposure to noise or air pollution during pregnancy did not seem to pose a risk for development of congenital anomalies.

Indoor Wood-Burning Stove and Fireplace Use and Breast Cancer in a Prospective Cohort Study

BACKGROUND

Indoor burning of fuel for heating or cooking releases carcinogens. Little is known about the impact of indoor air pollution from wood-burning stoves or fireplaces on breast cancer risk.

OBJECTIVES

In a large prospective cohort study, we evaluated the risk of breast cancer in relation to indoor heating and cooking practices.

METHODS

Sister Study participants (n=50,884) were recruited from 2003–2009. Breast cancer–free women in the United States or Puerto Rico, 35–74 y old, with a sister with breast cancer were eligible. Participants completed questionnaires on indoor heating and cooking practices for both their enrollment and their longest adult residence. Cox regression was used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) for the association between indoor heating/cooking and breast cancer.

RESULTS

A total of 2,416 breast cancer cases were diagnosed during follow-up (mean=6.4 y). Having an indoor wood-burning stove/fireplace in the longest adult residence was associated with a higher breast cancer risk [HR=1.11 (95% CI: 1.01, 1.22)]; the risk increased with average frequency of use [≥once/week, HR=1.17 (95% CI: 1.02, 1.34)] (p for trend=0.01). An elevated HR was seen for women burning wood [HR=1.09 (95% CI: 0.98, 1.21)] or natural gas/propane [HR=1.15 (95% CI: 1.00, 1.32)]. No association was observed for burning artificial fire-logs [HR=0.98 (95% CI: 0.85, 1.12)] except among women from western states [HR=1.36 (95% CI: 1.02, 1.81)].

CONCLUSIONS

In this prospective study, using an indoor wood-burning stove/fireplace in the longest adult residence at least once a week and burning either wood or natural gas/propane was associated with a modestly higher risk of breast cancer. https://doi.org/10.1289/EHP827.

Biomarkers used in studying air pollution exposure during pregnancy and perinatal outcomes: a review

PURPOSE

This review focuses on studies among pregnant women that used biomarkers to assess air pollution exposure, or to understand the mechanisms by which it affects perinatal outcomes.

METHODS

We searched PubMed and Google scholar databases to find articles.

RESULTS AND CONCLUSIONS

We found 29 articles, mostly consisting of cohort studies. Interpolation models were most frequently used to assess exposure. The most consistent positive association was between polycyclic aromatic hydrocarbon (PAH) exposure during entire pregnancy and cord blood PAH DNA adducts. Exposure to particulate matter (PM) and nitrogen dioxide (NO₂) showed consistent inverse associations with mitochondrial DNA (mtDNA) content, particularly in the third trimester of pregnancy. No single pollutant showed strong associations with all the biomarkers included in this review. C-reactive proteins (CRPs) and oxidative stress markers increased, whereas telomere length decreased with increasing air pollution exposure. Placental global DNA methylation and mtDNA methylation showed contrasting results with air pollution exposure, the mechanism behind which is unclear. Most studies except those on PAH DNA adducts and mtDNA content provided insufficient evidence for characterizing a critical exposure window. Further research using biomarkers is warranted to understand the relationship between air pollution and perinatal outcomes.

Transplacental exposure to environmental carcinogens: Association with childhood cancer risks and the role of modulating factors

Biological responses to carcinogens from environmental exposure during adulthood are modulated over years or decades. Conversely, during transplacental exposure, the effects on the human foetus change within weeks, intertwining with developmental mechanisms: even short periods of transplacental exposure may be imprinted in the organism for a lifetime. The pathways leading to childhood and juvenile cancers, such as leukaemias, neuroblastoma/brain tumours, hepatoblastoma, and Willm's tumour involve prenatally-induced genomic, epigenomic and/or non-genomic effects caused by xenobiotics. Pregnant women most often live in complex environmental settings that cause transplacental exposure of the foetus to xenobiotic mixtures. Mother-child biomonitoring should integrate the analysis of chemicals/radiation present in the living and workplace environment with relevant risk modulators related to life style. The interdisciplinary approach for transplacental cancer risk assessment in high-pressure areas should be based on an integrated model for mother-child exposure estimation via profiling the exposure level by water quality analysis, usage of emission grids, and land use maps.

Newborn sex-specific transcriptome signatures and gestational exposure to fine particles: findings from the ENVIRONAGE birth cohort

BACKGROUND

Air pollution exposure during pregnancy has been associated with adverse birth outcomes and health problems later in life. We investigated sex-specific transcriptomic responses to gestational long- and short-term exposure to particulate matter with a diameter < 2.5 μm (PM_2.5) in order to elucidate potential underlying mechanisms of action.

METHODS

Whole genome gene expression was investigated in cord blood of 142 mother-newborn pairs that were enrolled in the ENVIRONAGE birth cohort. Daily PM_2.5 exposure levels were calculated for each mother's home address using a spatial-temporal interpolation model in combination with a dispersion model to estimate both long- (annual average before delivery) and short- (last month of pregnancy) term exposure. We explored the association between gene expression levels and PM_2.5 exposure, and identified modulated pathways by overrepresentation analysis and gene set enrichment analysis.

RESULTS

Some processes were altered in both sexes for long- (e.g. DNA damage) or short-term exposure (e.g. olfactory signaling). For long-term exposure in boys neurodevelopment and RhoA pathways were modulated, while in girls defensin expression was down-regulated. For short-term exposure we identified pathways related to synaptic transmission and mitochondrial function (boys) and immune response (girls).

CONCLUSIONS

This is the first whole genome gene expression study in cord blood to identify sex-specific pathways altered by PM_2.5. The identified transcriptome pathways could provide new molecular insights as to the interaction pattern of early life PM_2.5 exposure with the biological development of the fetus.

Micronucleus, cell-free DNA, and plasma glycan composition in the newborns of healthy and diabetic mothers

Diabetes is associated with certain environmental exposures, heritable factors, and metabolic conditions of intrauterine development due to diabetes in the mother. We evaluated genomic damage, cell-free DNA, N-glycosylation of umbilical cord plasma proteins (PG), and nuclear division index (NDI) as possible prognostic biomarkers of health risk in the newborns of mothers with treated pregestational diabetes (NBDM; 22 mothers), compared these parameters with those from newborns of healthy mothers (NBHM; 89 mothers), and associated the results with the mothers' lifestyle in both groups, based on a detailed questionnaire. Genomic damage was estimated by the in vitro micronucleus (MN) assay. NDI was detected on MN slides. Glycans were analyzed by ultra-performance liquid chromatography that separates the plasma N-glycome into 46 glycan peaks. Cell-free DNA was analyzed by real-time PCR. For the association between biomarkers and individual characteristics, generalized linear/nonlinear analysis was performed. No significant difference was found between NBHM and NBDM for cell-free DNA levels. There was no association between cell-free DNA levels and lifestyle. MN frequency was significantly higher in NBDM than in NBHM (median, 0.6 vs. 0.3%, p<0.001). MN frequency and NDI were significantly associated with residence (urban vs. rural). PG differed significantly between NBHM and NBDM (p<0.001). A significant association was found between PG and increase of MN frequency (p<0.001). As both MN frequency and altered N-glycosylation are associated with cancer risk, our study indicates need for further investigations.

Cytogenetic biomarkers in detection of genotoxic effects of gestagens in peripheral blood lymphocytes in vitro and in vivo

Gestagens are the most frequently used steroid hormones in hormone-replacement therapy in the treatment of threatened miscarriage during the first trimester of pregnancy. This therapy has been applied in a large number of women with threatened abortion, despite various degrees of success of its efficacy. Genetic factors play a key role in miscarriages, especially in the initial stages. Cytogenetic biomarkers such as micronucleus (MN) test, chromosomal aberrations (CAs), and sister chromatid exchanges (SCEs) provide information on DNA damage. Cytogenetic markers detecting DNA damage have become very popular and useful in analysing genetic risk associated with hormone-replacement therapy. Cytogenetic studies presented heterogenous information. In many in vitro studies synthetic gestagens have been shown to induce genotoxic effects, and it was evaluated using three cytogenetic biomarkers. Genotoxic effects of gestagens have also been confirmed in in vivo studies that were conducted involving patients who received gestagen therapy during pregnancy and their newborns. However, some studies have shown that hormone-replacement therapy does not have genotoxic effects. In this paper, we summarize the results from previous studies. We also describe the usefulness of these biomarkers in the detection of genotoxic effects of hormone-replacement therapy.

Maternal diet during pregnancy and micronuclei frequency in peripheral blood T lymphocytes in mothers and newborns (Rhea cohort, Crete)

PURPOSE

The study assessed whether diet and adherence to cancer prevention guidelines during pregnancy were associated with micronucleus (MN) frequency in mothers and newborns. MN is biomarkers of early genetic effects that have been associated with cancer risk in adults.

METHODS

A total of 188 mothers and 200 newborns from the Rhea cohort (Greece) were included in the study. At early-mid pregnancy, we conducted personal interviews and a validated food frequency questionnaire was completed. With this information, we constructed a score reflecting adherence to the World Cancer Research Fund/American Institute for Cancer Research cancer prevention guidelines on diet, physical activity and body fatness. At delivery, maternal and/or cord blood was collected to measure DNA and hemoglobin adducts of dietary origin and frequencies of MN in binucleated and mononucleated T lymphocytes (MNBN and MNMONO).

RESULTS

In mothers, higher levels of red meat consumption were associated with increased MNBN frequency [2nd tertile IRR = 1.34 (1.00, 1.80), 3rd tertile IRR = 1.33 (0.96, 1.85)] and MNMONO frequency [2nd tertile IRR = 1.53 (0.84, 2.77), 3rd tertile IRR = 2.69 (1.44, 5.05)]. The opposite trend was observed for MNBN in newborns [2nd tertile IRR = 0.64 (0.44, 0.94), 3rd tertile IRR = 0.68 (0.46, 1.01)], and no association was observed with MNMONO. Increased MN frequency in pregnant women with high red meat consumption is consistent with previous knowledge.

CONCLUSIONS

Our results also suggest exposure to genotoxics during pregnancy might affect differently mothers and newborns. The predictive value of MN as biomarker for childhood cancer, rather than adulthood, remains unclear. With few exceptions, the association between maternal carcinogenic exposures during pregnancy and childhood cancer or early biologic effect biomarkers remains poorly understood.

Fine particle-induced birth defects: Impacts of size, payload, and beyond

Worldwide epidemiological studies have shown that exposures to particulate matters (PMs), such as PM_2.5 or PM₁₀ , during pregnancy cause birth defects in the newborn. Although mechanistic understanding of such effects are not available, recent research using murine models highlights some key progress: (1) toxicity caused by PMs is a combined effects of particles and the adsorbed toxic pollutants, such as heavy metals, persistent organic pollutants, bacteria, and virus. Fine particles may hold on to pollutants and, therefore, reduce their toxicity or enhance the toxicity by carrying pollutants crossing the placental barrier; (2) smaller size, certain particle surface chemistry modifications, early developmental stage of placenta, and maternal diseases all aggravate PM-induced birth defects; (3) molecular events involved in such toxicity are begin to emerge: induction of oxidative stress, DNA damage, and alteration of molecular signaling or epigenetic events are some possible causes. Despite this progress, a clear understanding of PM-induced birth defects awaits further breakthroughs on many fronts, including epidemiological studies, animal models, nanotoxicity, and molecular mechanism investigations. Birth Defects Research (Part C) 108:196-206, 2016. © 2016 Wiley Periodicals, Inc.

Air toxics and early childhood acute lymphocytic leukemia in Texas, a population based case control study

BACKGROUND

Traffic exhaust, refineries and industrial facilities are major sources of air toxics identified by the U.S. Environmental Protection Agency (U.S. EPA) for their potential risk to human health. In utero and early life exposures to air toxics such as benzene and 1,3-butadiene, which are known leukemogens in adults, may play an etiologic role in childhood leukemia that comprises the majority of pediatric cancers. We conducted a population based case-control study to examine individual effects of benzene, 1,3-butadiene and polycyclic organic matter (POM) in ambient residential air on acute lymphocytic leukemia (ALL) diagnosed in children under age 5 years in Texas from 1995-2011.

METHODS

Texas Cancer Registry cases were linked to birth records and then were frequency matched by birth month and year to 10 population-based controls. Maternal and infant characteristics from birth certificates were abstracted to obtain information about potential confounders. Modelled estimates of benzene, 1,3-butadiene and POM exposures at the census tract level were assigned by linking geocoded maternal addresses from birth certificates to U.S. EPA National-Scale Air Toxics Assessment data for single and co-pollutant statistical analyses. Mixed-effects logistic regression models were applied to evaluate associations between air toxics and childhood leukemia.

RESULTS

In adjusted single pollutant models, odds of childhood leukemia among mothers with the highest ambient air exposures compared to those in the lowest quartile were 1.11 (95 % CI: 0.94-1.32) for POM, 1.17 (95 % CI: 0.98-1.39) for benzene and 1.29 (95 % CI: 1.08-1.52) for 1,3-butadiene. In co-pollutant models, odds ratios for childhood leukemia remained elevated for 1,3-butadiene but were close to the null value for benzene and POM.

CONCLUSIONS

We observed positive associations between 1,3-butadiene and childhood leukemia in single and co-pollutant models whereas effect estimates from single pollutant models were diminished for benzene and POM in co-pollutant models. Early life exposure to 1,3-butadiene rather than benzene or POM appears to increase early childhood risk of acute lymphocytic leukemia.

Associations of maternal personal exposure to air pollution on fetal weight and fetoplacental Doppler: A prospective cohort study

We determined the influence of maternal air pollution exposure during each trimester of pregnancy on fetal and birth weight and fetoplacental hemodynamics. In total, 366 women with singleton pregnancies were prospectively followed in the city of São Paulo, Brazil. Nitrogen dioxide (NO2) and ozone (O3) were measured during each trimester using passive personal samplers. We evaluated fetal weight and Doppler velocimetry data from the umbilical, middle cerebral, and uterine arteries in the 3rd trimester, and birth weight. Multivariate analysis was performed, controlling for known determinants of fetal weight. Exposure to higher levels of O3 during the 2nd trimester was associated with higher umbilical artery pulsatility indices (PIs) [p=0.013; beta=0.017: standard error (SE)=0.007]. Exposure to higher levels of O3 during the 3rd trimester was associated with lower umbilical artery PIs (p=0.011; beta=-0.021; SE=0.008). Our results suggest that in the environment of São Paulo, O3 may affects placental vascular resistance.

Outdoor air pollution exposures and micronuclei frequencies in lymphocytes from pregnant women and newborns in Crete, Greece (Rhea cohort)

BACKGROUND

Micronuclei (MN) are biomarkers of early genetic effects that have been used to investigate the association between environmental exposures and cancer. However, few studies have examined the association between environmental exposures during pregnancy and MN in mothers and newborns.

OBJECTIVES

We examined MN frequency in maternal blood and in cord blood, in relation to maternal air pollution exposure, and the potential interaction with maternal vitamin C intake and maternal smoking.

METHODS

We used the cytokinesis-block micronucleus assay to assess MN frequency per 1000 bi-nucleated T-lymphocytes from 181 mothers and 183 newborns born in 2007-2008 in Heraklion (Crete, Greece). The ESCAPE land-use regression methods were used to estimate annual mean exposure to outdoor air pollution [particulate matter (PM), black carbon, nitrogen dioxide (NO2) and nitrogen oxides (NOx)] at maternal home addresses. Food frequency questionnaires were used to estimate maternal dietary vitamin C intake during pregnancy. Smoking habits were self-reported using questionnaires which were checked by measuring maternal urinary cotinine levels.

RESULTS

Exposure to PM2.5 was associated with increased MN frequencies in pregnant women [rate ratio [RR (95%CI)] per 5 µg/m(3)=1.53 (1.02, 2.29)]. This increase was considerably higher among women who did not fulfill the recommended vitamin C dietary allowances [RR=9.35 (2.77, 31.61); n=20]. Exposure to PM2.5-10, PM10, NO2 and NOx were also associated with a higher incidence of MN frequencies in smoker women (n=56). No associations were found for newborns.

CONCLUSIONS

We found an association between air pollution, particularly PM2.5, and MN frequency in mothers but not in newborns. This association was more pronounced among women with a lower dietary intake of vitamin C during pregnancy and among women who smoked during pregnancy. While results are clear in mothers, the association between maternal carcinogenic exposures during pregnancy and biomarkers of early biologic effect in the newborn remains poorly understood.

Air pollution and public health: emerging hazards and improved understanding of risk

Despite past improvements in air quality, very large parts of the population in urban areas breathe air that does not meet European standards let alone the health-based World Health Organisation Air Quality Guidelines. Over the last 10 years, there has been a substantial increase in findings that particulate matter (PM) air pollution is not only exerting a greater impact on established health endpoints, but is also associated with a broader number of disease outcomes. Data strongly suggest that effects have no threshold within the studied range of ambient concentrations, can occur at levels close to PM2.5 background concentrations and that they follow a mostly linear concentration-response function. Having firmly established this significant public health problem, there has been an enormous effort to identify what it is in ambient PM that affects health and to understand the underlying biological basis of toxicity by identifying mechanistic pathways-information that in turn will inform policy makers how best to legislate for cleaner air. Another intervention in moving towards a healthier environment depends upon the achieving the right public attitude and behaviour by the use of optimal air pollution monitoring, forecasting and reporting that exploits increasingly sophisticated information systems. Improving air quality is a considerable but not an intractable challenge. Translating the correct scientific evidence into bold, realistic and effective policies undisputedly has the potential to reduce air pollution so that it no longer poses a damaging and costly toll on public health.

Micronucleus frequency in Danish schoolchildren and their mothers from the DEMOCOPHES population

Micronucleus (MN) frequency is a biomarker for early genetic effects which is often used in human biomonitoring studies. Increased frequency of micronuclei has been associated with high levels of traffic exposure. Further high MN frequency was found predictive for cancer development in several studies of adults. In the present study, the MN frequency in blood samples from the Danish participants of the European pilot project DEMOCOPHES was analysed and related to the area of residence, self-reported and calculated exposure to road traffic as well as to mercury in hair and blood concentrations of persistent organic pollutants and dioxin-like activity measured in the same participants. The MN frequency analysis was performed with the cytokinesis-block micronucleus (CBMN) assay and included 100 children and 119 mothers. We found a significant correlation between mothers and children in the levels of micronuclei in 1000 binucleated T lymphocytes (‰MNBN) and in the proliferation index. Further the levels of ‰MNBN were significantly higher in mothers compared with their children. No significant associations were found for ‰MNBN for traffic related exposure in neither children nor their mothers. In children, a 2.5 times higher micronuclei in mononuclear T lymphocytes were found in children living within 50 m of a busy road, however, this was not found in mothers or in MNBN and the effect of exposure to road traffic on MN frequency needs further investigation. No significant associations were found between MN frequencies and the other biomarkers measured in the same participants.

Environmental, dietary, maternal, and fetal predictors of bulky DNA adducts in cord blood: a European mother-child study (NewGeneris)

BACKGROUND

Bulky DNA adducts reflect genotoxic exposures, have been associated with lower birth weight, and may predict cancer risk.

OBJECTIVE

We selected factors known or hypothesized to affect in utero adduct formation and repair and examined their associations with adduct levels in neonates.

METHODS

Pregnant women from Greece, Spain, England, Denmark, and Norway were recruited in 2006-2010. Cord blood bulky DNA adduct levels were measured by the 32P-postlabeling technique (n = 511). Diet and maternal characteristics were assessed via questionnaires. Modeled exposures to air pollutants and drinking-water disinfection by-products, mainly trihalomethanes (THMs), were available for a large proportion of the study population.

RESULTS

Greek and Spanish neonates had higher adduct levels than the northern European neonates [median, 12.1 (n = 179) vs. 6.8 (n = 332) adducts per 108 nucleotides, p < 0.001]. Residence in southern European countries, higher maternal body mass index, delivery by cesarean section, male infant sex, low maternal intake of fruits rich in vitamin C, high intake of dairy products, and low adherence to healthy diet score were statistically significantly associated with higher adduct levels in adjusted models. Exposure to fine particulate matter and nitrogen dioxide was associated with significantly higher adducts in the Danish subsample only. Overall, the pooled results for THMs in water show no evidence of association with adduct levels; however, there are country-specific differences in results with a suggestion of an association in England.

CONCLUSION

These findings suggest that a combination of factors, including unknown country-specific factors, influence the bulky DNA adduct levels in neonates.

Carcinogenicity of ambient air pollution: use of biomarkers, lessons learnt and future directions

The association between ambient air pollution (AAP) exposure and lung cancer risk has been investigated in prospective studies and the results are generally consistent, indicating that long-term exposure to air pollution can cause lung cancer. Biomarkers can enhance research on the health effects of air pollution by improving exposure assessment, increasing the understanding of mechanisms, and enabling the investigation of individual susceptibility. In this review, we assess DNA adducts as biomarkers of exposure to AAP and early biological effect, and DNA methylation as biomarker of early biological change and discuss critical issues arising from their incorporation in AAP health impact evaluations, such as confounding, individual susceptibilities, timing, intensity and duration of exposure, and investigated tissue. DNA adducts and DNA methylation are treated as paradigms. However, the lessons, learned from their use in the examination of AAP carcinogenicity, can be applied to investigations of other biomarkers involved in AAP carcinogenicity.

Levels of PAH-DNA adducts in cord blood and cord tissue and the risk of fetal neural tube defects in a Chinese population

INTRODUCTION

Maternal exposure to polycyclic aromatic hydrocarbons (PAHs) has been shown to be associated with an elevated risk for neural tube defects (NTDs). In the human body, PAHs are bioactivated and the resultant reactive epoxides can covalently bind to DNA to form PAH-DNA adducts, which may, in turn, cause transcription errors, changes in gene expression or altered patterns of apoptosis. During critical developmental phases, these changes can result in abnormal morphogenesis.

OBJECTIVES

We aimed to examine the relationship between the levels of PAH-DNA adducts in cord blood and cord tissue and the risk of NTDs.

METHODS

From 2010 to 2012, 60 NTD cases and 60 healthy controls were recruited from a population-based birth defects surveillance system in five counties of Shanxi Province in Northern China, where the emission of PAHs remains one of the highest in the country and PAHs exposure is highly prevalent. PAH-DNA adducts in cord blood of 15 NTD cases and 15 control infants, and in cord tissue of 60 NTD cases and 60 control infants were measured using the (32)P-postlabeling method.

RESULTS

PAH-DNA adduct levels in cord blood tend to be higher in the NTD group (28.5 per 10(8) nucleotides) compared with controls (19.7 per 10(8) nucleotides), although the difference was not statistically significant (P=0.377). PAH-DNA adducts in cord tissue were significantly higher in the NTD group (24.6 per 10(6) nucleotides) than in the control group (15.3 per 10(6) nucleotides), P=0.010. A positive dose-response relationship was found between levels of PAH-DNA adducts in cord tissue and the risk of NTDs (P=0.009). When the lowest tertile was used as the referent and potential confounding factors were adjusted for, a 1.03-fold (95% CI, 0.37-2.89) and 2.96-fold (95% CI, 1.16-7.58) increase in the risk of NTDs was observed for fetuses whose cord tissue PAH-DNA adduct levels were in the second and highest tertile, respectively.

CONCLUSIONS

High levels of PAH-DNA adducts in fetal tissues were associated with increased risks of NTDs.

Indoor air pollution exposure from use of indoor stoves and fireplaces in association with breast cancer: a case-control study

BACKGROUND

Previous studies suggest that polycyclic aromatic hydrocarbons (PAHs) may adversely affect breast cancer risk. Indoor air pollution from use of indoor stoves and/or fireplaces is an important source of ambient PAH exposure. However, the association between indoor stove/fireplace use and breast cancer risk is unknown. We hypothesized that indoor stove/fireplace use in a Long Island, New York study population would be positively associated with breast cancer and differ by material burned, and the duration and timing of exposure. We also hypothesized that the association would vary by breast cancer subtype defined by p53 mutation status, and interact with glutathione S-transferases GSTM1, T1, A1 and P1 polymorphisms.

METHODS

Population-based, case-control resources (1,508 cases/1,556 controls) were used to conduct unconditional logistic regression to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Breast cancer risk was increased among women reporting ever burning synthetic logs (which may also contain wood) in their homes (OR = 1.42, 95% CI 1.11, 1.84), but not for ever burning wood alone (OR = 0.93, 95% CI 0.77, 1.12). For synthetic log use, longer duration >7 years, older age at exposure (>20 years; OR = 1.65, 95% CI 1.02, 2.67) and 2 or more variants in GSTM1, T1, A1 or P1 (OR = 1.71, 95% CI 1.09, 2.69) were associated with increased risk.

CONCLUSIONS

Burning wood or synthetic logs are both indoor PAH exposure sources; however, positive associations were only observed for burning synthetic logs, which was stronger for longer exposures, adult exposures, and those with multiple GST variant genotypes. Therefore, our results should be interpreted with care and require replication.

Particulate matter beyond mass: recent health evidence on the role of fractions, chemical constituents and sources of emission

Particulate matter (PM) is regulated in various parts of the world based on specific size cut offs, often expressed as 10 or 2.5 µm mass median aerodynamic diameter. This pollutant is deemed one of the most dangerous to health and moreover, problems persist with high ambient concentrations. Continuing pressure to re-evaluate ambient air quality standards stems from research that not only has identified effects at low levels of PM but which also has revealed that reductions in certain components, sources and size fractions may best protect public health. Considerable amount of published information have emerged from toxicological research in recent years. Accumulating evidence has identified additional air quality metrics (e.g. black carbon, secondary organic and inorganic aerosols) that may be valuable in evaluating the health risks of, for example, primary combustion particles from traffic emissions, which are not fully taken into account with PM2.5 mass. Most of the evidence accumulated so far is for an adverse effect on health of carbonaceous material from traffic. Traffic-generated dust, including road, brake and tire wear, also contribute to the adverse effects on health. Exposure durations from a few minutes up to a year have been linked with adverse effects. The new evidence collected supports the scientific conclusions of the World Health Organization Air Quality Guidelines and also provides scientific arguments for taking decisive actions to improve air quality and reduce the global burden of disease associated with air pollution.

Maternal diet, prenatal exposure to dioxin-like compounds and birth outcomes in a European prospective mother-child study (NewGeneris)

Maternal diet can result in exposure to environmental contaminants including dioxins which may influence foetal growth. We investigated the association between maternal diet and birth outcomes by defining a dioxin-rich diet. We used validated food frequency questionnaires to assess the diet of pregnant women from Greece, Spain, United Kingdom, Denmark and Norway and estimated plasma dioxin-like activity by the Dioxin-Responsive Chemically Activated LUciferase eXpression (DR-CALUX®) bioassay in 604 maternal blood samples collected at delivery. We applied reduced rank regression to identify a dioxin-rich dietary pattern based on dioxin-like activity (DR-CALUX®) levels in maternal plasma, and calculated a dioxin-diet score as an estimate of adherence to this dietary pattern. In the five country population, dioxin-diet score was characterised by high consumption of red and white meat, lean and fatty fish, low-fat dairy and low consumption of salty snacks and high-fat cheese, during pregnancy. The upper tertile of the dioxin-diet score was associated with a change in birth weight of -121g (95% confidence intervals: -232, -10g) compared to the lower tertile after adjustment for confounders. A small non-significant reduction in gestational age was also observed (-1.4days, 95% CI: -3.8, 1.0days). Our results suggest that maternal diet might contribute to the exposure of the foetus to dioxins and dioxin-like compounds and may be related to reduced birth weight. More studies are needed to develop updated dietary guidelines for women of reproductive age, aiming to the reduction of dietary exposure to persistent organic pollutants as dioxins and dioxin-like compounds.

DNA damage in buccal mucosa cells of pre-school children exposed to high levels of urban air pollutants

Air pollution has been recognized as a human carcinogen. Children living in urban areas are a high-risk group, because genetic damage occurring early in life is considered able to increase the risk of carcinogenesis in adulthood. This study aimed to investigate micronuclei (MN) frequency, as a biomarker of DNA damage, in exfoliated buccal cells of pre-school children living in a town with high levels of air pollution. A sample of healthy 3-6-year-old children living in Brescia, Northern Italy, was investigated. A sample of the children's buccal mucosa cells was collected during the winter months in 2012 and 2013. DNA damage was investigated using the MN test. Children's exposure to urban air pollution was evaluated by means of a questionnaire filled in by their parents that included items on various possible sources of indoor and outdoor pollution, and the concentration of fine particulate matter (PM10, PM2.5) and NO2 in the 1-3 weeks preceding biological sample collection. 181 children (mean age ± SD: 4.3 ± 0.9 years) were investigated. The mean ± SD MN frequency was 0.29 ± 0.13%. A weak, though statistically significant, association of MN with concentration of air pollutants (PM10, PM2.5 and NO2) was found, whereas no association was apparent between MN frequency and the indoor and outdoor exposure variables investigated via the questionnaire. This study showed a high MN frequency in children living in a town with heavy air pollution in winter, higher than usually found among children living in areas with low or medium-high levels of air pollution.

A curated review of recent literature of biomarkers used for assessing air pollution exposures and effects in humans

This is a cross-sectional review of biomarkers used in air pollution research from January 2009 through December 2012. After an initial keyword search in PubMed retrieving 426 articles, a comprehensive abstract review identified 54 articles of experimental design that used biomarkers of exposure or effect in human studies in the area of air pollution research during this specified time period. A thorough bibliographic search of the included articles retrieved an additional 65 articles meeting the inclusion criteria. This review presents these 119 studies and the 234 biomarkers employed in these air pollution research investigations. Data presented are 70 biomarkers of exposure with 54% relating to polycyclic aromatic hydrocarbons, 36% volatile organic carbons, and 10% classified as other. Of the 164 biomarkers of effect, 91 and 130 were used in investigating effects of short-term and chronic exposure, respectively. Results of biomarkers used in short-term exposure describe different lag times and pollutant components such as primary and secondary pollutants, and particle number associated with corresponding physiological mechanisms including airway inflammation, neuroinflammation, ocular, metabolic, early endothelial dysfunction, coagulation, atherosclerosis, autonomic nervous system, oxidative stress, and DNA damage. The review presents three different exposure scenarios of chronic, occupational, and extreme exposure scenarios (indoor cooking) with associated biomarker findings presented in three broad categories of (1) immune profile, (2) oxidative stress, and (3) DNA damage. This review offers a representation of the scope of data being explored by air pollution researchers through the use of biomarkers and has deliberately been restricted to this particular subject rather than an extensive or in-depth review. This article provides a contextualization of air pollution studies conducted with biomarkers in human subjects in given areas while also integrating this complex body of information to offer a useful review for investigators in this field of study.

Exposure to brominated trihalomethanes in water during pregnancy and micronuclei frequency in maternal and cord blood lymphocytes

BACKGROUND

Water disinfection by-products have been associated with an increased cancer risk. Micronuclei (MN) frequency in lymphocytes is a marker of genomic damage and can predict adult cancer risk.

OBJECTIVE

We evaluated maternal exposure to drinking water brominated trihalomethanes (BTHM) in relation to MN frequency in maternal and cord blood lymphocytes.

METHODS

MN frequency was examined in 214 mothers and 223 newborns from the Rhea mother-child cohort in Crete, Greece, in 2007-2008. Residential BTHM water concentrations were estimated during pregnancy using tap water analyses and modeling. Questionnaires on water related habits were used to estimate BTHM exposure from all routes. Associations between BTHM and MN frequency were estimated using negative binomial regression.

RESULTS

BTHM concentrations in residential tap water during pregnancy ranged from 0.06 to 7.1 μg/L. MN frequency in maternal binucleated lymphocytes was found to increase with BTHM concentrations in residential water for exposure during the first [rate ratio (RR) for 1 μg/L=1.05; 95% CI: 1.00, 1.11] and second trimesters (RR for 1 μg/L=1.03; 95% CI: 1.00, 1.06), and through all routes of BTHM exposure during the first trimester (RR for 1 μg/week=3.14; 95% CI: 1.16, 8.50).

CONCLUSIONS

These findings suggest that exposure to BTHM may increase the frequency of MN in maternal binucleated lymphocytes.

Risk of leukemia in relation to exposure to ambient air toxics in pregnancy and early childhood

There are few established causes of leukemia, the most common type of cancer in children. Studies in adults suggest a role for specific environmental agents, but little is known about any effect from exposures in pregnancy to toxics in ambient air. In our case-control study, we ascertained 69 cases of acute lymphoblastic leukemia (ALL) and 46 cases of acute myeloid leukemia (AML) from California Cancer Registry records of children <age 6, and 19,209 controls from California birth records within 2 km (1.3 miles) (ALL) and 6 km (3.8 miles) (AML) of an air toxics monitoring station between 1990 and 2007. Information on air toxics exposures was taken from community air monitors. We used logistic regression to estimate the risk of leukemia associated with one interquartile range increase in air toxic exposure. Risk of ALL was elevated with 3(rd) trimester exposure to polycyclic aromatic hydrocarbons (OR=1.16, 95% CI 1.04, 1.29), arsenic (OR=1.33, 95% CI 1.02, 1.73), benzene (OR=1.50, 95% CI 1.08, 2.09), and three other toxics related to fuel combustion. Risk of AML was increased with 3rd trimester exposure to chloroform (OR=1.30, 95% CI 1.00, 1.69), benzene (1.75, 95% CI 1.04, 2.93), and two other traffic-related toxics. During the child's first year, exposure to butadiene, ortho-xylene, and toluene increased risk for AML and exposure to selenium increased risk for ALL. Benzene is an established cause of leukemia in adults; this study supports that ambient exposures to this and other chemicals in pregnancy and early life may also increase leukemia risk in children.

Lower nucleotide excision repair capacity in newborns compared to their mothers: a pilot study

Recognition of the potential vulnerability of children and newborns and protection of their health is essential, especially regarding to genotoxic compounds. Benzo(a)pyrene B(a)P a commonly found carcinogen, and its metabolite BPDE, are known to cross the placenta. To investigate how well newborns are able to cope with BPDE-induced DNA damage, a recent developed nucleotide excision repair cell phenotype assay was applied in a pilot study of 25 newborn daughters and their mothers, using the Alkaline Comet Assay and taking demographic data into account. Newborns seemed to be less able to repair BPDE-induced DNA damage since lower repair capacity levels were calculated compared to their mothers although statistical significance was not reached. Assessment of repair capacity in combination with genotypes will provide important information to support preventive strategies in neonatal care and to define science based exposure limits for pregnant women and children.