Cross-sectional Associations between Exposure to Persistent Organic Pollutants and Leukocyte Telomere Length among U.S. Adults in NHANES, 2001-2002

BACKGROUND

Exposure to persistent organic pollutants (POPs) such as dioxins, furans, and polychlorinated biphenyls (PCBs) may influence leukocyte telomere length (LTL), a biomarker associated with chronic disease. In vitro research suggests dioxins may bind to the aryl hydrocarbon receptor (AhR) and induce telomerase activity, which elongates LTL. However, few epidemiologic studies have investigated associations between POPs and LTL.

OBJECTIVES

We examined the association between 18 PCBs, 7 dioxins, and 9 furans and LTL among 1,330 U.S. adults from NHANES 2001-2002.

METHODS

We created three summed POP metrics based on toxic equivalency factor (TEF), a potency measure including affinity for the AhR: a) non-dioxin-like PCBs (composed of 10 non-dioxin-like PCBs; no AhR affinity and no TEF); b) non-ortho PCBs (composed of 2 non-ortho-substituted PCBs with high TEFs); and c) toxic equivalency (TEQ) (composed of 7 dioxins, 9 furans, 2 non-ortho-substituted PCBs, and 6 mono-ortho-substituted PCBs; weighted by TEF). We tested the association between each metric and LTL using linear regression, adjusting for demographics, blood cell count and distribution, and another metric with a different TEF (i.e., non-ortho PCBs and TEQ adjusted for non-dioxin-like PCBs; non-dioxin-like PCBs adjusted for non-ortho PCBs).

RESULTS

In adjusted models, each doubling of serum concentrations of non-ortho PCBs and TEQ was associated with 3.74% (95% CI: 2.10, 5.40) and 5.29% (95% CI: 1.66, 9.05) longer LTLs, respectively. Compared with the lowest quartile, the highest quartile of exposure was associated with 9.16% (95% CI: 2.96, 15.73) and 7.84% (95% CI: -0.53, 16.92) longer LTLs, respectively. Non-dioxin-like PCBs were not associated with LTL.

CONCLUSIONS

POPs with high TEFs and AhR affinity were associated with longer LTL. Because many dioxin-associated cancers are also associated with longer LTL, these results may provide insight into the mechanisms underlying PCB- and dioxin-related carcinogenesis.

CITATION

Mitro SD, Birnbaum LS, Needham BL, Zota AR. 2016. Cross-sectional associations between exposure to persistent organic pollutants and leukocyte telomere length among U.S. adults in NHANES, 2001-2002. Environ Health Perspect 124:651-658; http://dx.doi.org/10.1289/ehp.1510187.

Uppsala Consensus Statement on Environmental Contaminants and the Global Obesity Epidemic

Summary: From the lectures presented at the 2nd International Workshop on Obesity and Environmental Contaminants, which was held in Uppsala, Sweden, on 8–9 October 2015, it became evident that the findings from numerous animal and epidemiological studies are consistent with the hypothesis that environmental contaminants could contribute to the global obesity epidemic. To increase awareness of this important issue among scientists, regulatory agencies, politicians, chemical industry management, and the general public, the authors summarize compelling scientific evidence that supports the hypothesis and discuss actions that could restrict the possible harmful effects of environmental contaminants on obesity.

E-Waste and Harm to Vulnerable Populations: A Growing Global Problem

BACKGROUND

Electronic waste (e-waste) is produced in staggering quantities, estimated globally to be 41.8 million tonnes in 2014. Informal e-waste recycling is a source of much-needed income in many low- to middle-income countries. However, its handling and disposal in underdeveloped countries is often unsafe and leads to contaminated environments. Rudimentary and uncontrolled processing methods often result in substantial harmful chemical exposures among vulnerable populations, including women and children. E-waste hazards have not yet received the attention they deserve in research and public health agendas.

OBJECTIVES

We provide an overview of the scale and health risks. We review international efforts concerned with environmental hazards, especially affecting children, as a preface to presenting next steps in addressing health issues stemming from the global e-waste problem.

DISCUSSION

The e-waste problem has been building for decades. Increased observation of adverse health effects from e-waste sites calls for protecting human health and the environment from e-waste contamination. Even if e-waste exposure intervention and prevention efforts are implemented, legacy contamination will remain, necessitating increased awareness of e-waste as a major environmental health threat.

CONCLUSION

Global, national, and local levels efforts must aim to create safe recycling operations that consider broad security issues for people who rely on e-waste processing for survival. Paramount to these efforts is reducing pregnant women and children's e-waste exposures to mitigate harmful health effects. With human environmental health in mind, novel dismantling methods and remediation technologies and intervention practices are needed to protect communities.

CITATION

Heacock M, Kelly CB, Asante KA, Birnbaum LS, Bergman AL, Bruné MN, Buka I, Carpenter DO, Chen A, Huo X, Kamel M, Landrigan PJ, Magalini F, Diaz-Barriga F, Neira M, Omar M, Pascale A, Ruchirawat M, Sly L, Sly PD, Van den Berg M, Suk WA. 2016. E-waste and harm to vulnerable populations: a growing global problem. Environ Health Perspect 124:550-555; http://dx.doi.org/10.1289/ehp.1509699.

Disposition of the emerging brominated flame retardant, bis(2-ethylhexyl) tetrabromophthalate, in female Sprague Dawley rats: effects of dose, route and repeated administration

1. Bis(2-ethylhexyl)-tetrabromophthalate (BEH-TEBP; CAS No. 26040-51-7; PubChem CID: 117291; MW 706.15 g/mol, elsewhere: TeBrDEPH, TBPH, or BEHTBP) is used as an additive brominated flame retardant in consumer products. 2. Female Sprague Dawley rats eliminated 92-98% of [¹⁴C]-BEH-TEBP unchanged in feces after oral administration (0.1 or 10 μmol/kg). A minor amount of each dose (0.8-1%) was found in urine after 72 h. Disposition of orally administered BEH-TEBP in male B6C3F1/Tac mice was similar to female rats. 3. Bioaccumulation of [¹⁴C]-radioactivity was observed in liver and adrenals following 10 daily oral administrations (0.1 μmol/kg/day). These tissues contained 5- and 10-fold higher concentrations of [¹⁴C]-radioactivity, respectively, versus a single dose. 4. IV-administered [¹⁴C]-BEH-TEBP (0.1 μmol/kg) was slowly eliminated in feces, with >15% retained in tissues after 72 h. Bile and fecal extracts from these rats contained the metabolite mono-ethylhexyl tetrabromophthalate (TBMEHP). 5. BEH-TEBP was poorly absorbed, minimally metabolized and eliminated mostly by the fecal route after oral administration. Repeated exposure to BEH-TEBP led to accumulation in some tissues. The toxicological significance of this effect remains to be determined. This work was supported by the Intramural Research Program of the National Cancer Institute at the National Institutes of Health (Project ZIA BC 011476).

Informing 21st-Century Risk Assessments with 21st-Century Science

Understanding and preventing adverse impacts from chemicals in the environment is fundamental to protecting public health, and chemical risk assessments are used to inform public health decisions in the United States and around the world. Traditional chemical risk assessments focus on health effects of environmental contaminants on a chemical-by-chemical basis, largely based on data from animal models using exposures that are typically higher than those experienced by humans. Results from environmental epidemiology studies sometimes show effects that are not observed in animal studies at human exposure levels that are lower than those used in animal studies. In addition, new approaches such as Toxicology in the 21st Century (Tox21) and exposure forecasting (ExpoCast) are generating mechanistic data that provide broad coverage of chemical space, chemical mixtures, and potential associated health outcomes, along with improved exposure estimates. It is becoming clear that risk assessments in the future will need to use the full range of available mechanistic, animal, and human data to integrate multiple types of data and to consider nontraditional health outcomes and end points. This perspective was developed at the "Strengthening the Scientific Basis of Chemical Safety Assessments" workshop, which was cosponsored by the U.S. Environmental Protection Agency and the National Institute of Environmental Health Sciences, where gaps between the emerging science and traditional chemical risk assessments were explored, and approaches for bridging the gaps were considered.

Bisphenol A, Bisphenol S, and 4-Hydro​xyphenyl 4-Isopro​oxyphenyl​sulfone (BPSIP) in Urine and Blood of Cashiers

BACKGROUND

Bisphenol A (BPA) is a high-production-volume chemical associated with a wide range of health outcomes in animal and human studies. BPA is used as a developer in thermal paper products, including cash register receipt paper; however, little is known about exposure of cashiers to BPA and alternative compounds in receipt paper.

OBJECTIVE

We determined whether handling receipt paper results in measurable absorption of BPA or the BPA alternatives bisphenol S (BPS) and 4-hydroxyphenyl 4-isoprooxyphenylsulfone (BPSIP).

METHODS

Cashiers (n = 77) and non-cashiers (n = 25) were recruited from the Raleigh-Durham-Chapel Hill region of North Carolina during 2011-2013. Receipts were analyzed for the presence of BPA or alternatives considered for use in thermal paper. In cashiers, total urine and serum BPA, BPS, and BPSIP levels in post-shift samples (collected ≤ 2 hr after completing a shift) were compared with pre-shift samples. Levels of these compounds in urine from cashiers were compared to levels in urine from non-cashiers.

RESULTS

Each receipt contained 1-2% by weight of the paper of BPA, BPS, or BPSIP. The post-shift geometric mean total urinary BPS concentration was significantly higher than the pre-shift mean in 33 cashiers who handled receipts containing BPS. The mean urine BPA concentrations in 31 cashiers who handled BPA receipts were as likely to decrease as to increase after a shift, but the mean post-shift concentrations were significantly higher than those in non-cashiers. BPSIP was detected more frequently in the urine of cashiers handling BPSIP receipts than in the urine of non-cashiers. Only a few cashiers had detectable levels of total BPA or BPS in serum, whereas BPSIP tended to be detected more frequently.

CONCLUSIONS

Thermal receipt paper is a potential source of occupational exposure to BPA, BPS, and BPSIP.

CITATION

Thayer KA, Taylor KW, Garantziotis S, Schurman SH, Kissling GE, Hunt D, Herbert B, Church R, Jankowich R, Churchwell MI, Scheri RC, Birnbaum LS, Bucher JR. 2016. Bisphenol A, bisphenol S, and 4-hydro​xyphenyl 4-isopro​oxyphenyl​sulfone (BPSIP) in urine and blood of cashiers. Environ Health Perspect 124:437-444; http://dx.doi.org/10.1289/ehp.1409427.

Associations Between Selected Xenobiotics and Antinuclear Antibodies in the National Health and Nutrition Examination Survey, 1999-2004

BACKGROUND

Potential associations between background environmental chemical exposures and autoimmunity are understudied.

OBJECTIVES

Our exploratory study investigated exposure to individual environmental chemicals and selected mixtures in relation to the presence of antinuclear antibodies (ANA), a widely used biomarker of autoimmunity, in a representative sample of the U.S.

METHODS

This cross-sectional analysis used data on 4,340 participants from the National Health and Nutrition Examination Survey (1999-2004), of whom 14% were ANA positive, to explore associations between ANA and concentrations of dioxins, dibenzofurans, polychlorinated biphenyls, organochlorines, organophosphates, phenols, metals, and other environmental exposures and metabolites measured in participants' serum, whole blood, or urine. For dioxin-like compounds with toxic equivalency factors, we developed and applied a new statistical approach to study selected mixtures. Lognormal models and censored-data methods produced estimates of chemical associations with ANA in males, nulliparous females, and parous females; these estimates were adjusted for confounders and accommodated concentrations below detectable levels.

RESULTS

Several associations between chemical concentration and ANA positivity were observed, but only the association in males exposed to triclosan remained statistically significant after correcting for multiple comparisons (mean concentration ratio = 2.8; 95% CI: 1.8, 4.5; p < 0.00001).

CONCLUSIONS

These data suggest that background levels of most xenobiotic exposures typical in the U.S. population are not strongly associated with ANA. Future studies should ideally reduce exposure misclassification by including prospective measurement of the chemicals of concern and should track changes in ANA and other autoantibodies over time.

CITATION

Dinse GE, Jusko TA, Whitt IZ, Co CA, Parks CG, Satoh M, Chan EKL, Rose KM, Walker NJ, Birnbaum LS, Zeldin DC, Weinberg CR, Miller FW. 2016. Associations between selected xenobiotics and antinuclear antibodies in the National Health and Nutrition Examination Survey, 1999-2004. Environ Health Perspect 124:426-436; http://dx.doi.org/10.1289/ehp.1409345.

Disruption of estrogen homeostasis as a mechanism for uterine toxicity in Wistar Han rats treated with tetrabromobisphenol A

Chronic oral treatment of tetrabromobisphenol A (TBBPA) to female Wistar Han rats resulted in increased incidence of cell proliferation at 250mg/kg and tumor formation in the uterus at higher doses. The present study was designed to test the hypothesis that disruption of estrogen homeostasis was a major mode-of-action for the observed effects. Biological changes were assessed in serum, liver, and the proximal (nearest the cervix) and distal (nearest the ovaries) sections of the uterine horn of Wistar Han rats 24h following administration of the last of five daily oral doses of 250mg/kg. Expression of genes associated with receptors, biosynthesis, and metabolism of estrogen was altered in the liver and uterus. TBBPA treatment also resulted in changes in expression of genes associated with cell division and growth. Changes were also observed in the concentration of thyroxine in serum and in expression of genes in the liver and uterus associated with thyroid hormone receptors. Differential expression of some genes was tissue-dependent or specific to tissue location in the uterus. The biological responses observed in the present study support the hypothesis that perturbation of estrogen homeostasis is a major mode-of-action for TBBPA-mediated cell proliferation and tumorigenesis previously observed in the uterus of TBBPA-treated Wistar Han rats.

Anniston community health survey: Follow-up and dioxin analyses (ACHS-II)--methods

High serum concentrations of polychlorinated biphenyls (PCBs) have been reported previously among residents of Anniston, Alabama, where a PCB production facility was located in the past. As the second of two cross-sectional studies of these Anniston residents, the Anniston Community Health Survey: Follow-Up and Dioxin Analyses (ACHS-II) will yield repeated measurements to be used to evaluate changes over time in ortho-PCB concentrations and selected health indicators in study participants. Dioxins, non-ortho PCBs, other chemicals, heavy metals, and a variety of additional clinical tests not previously measured in the original ACHS cohort will be examined in ACHS-II. The follow-up study also incorporates a questionnaire with extended sections on diet and occupational history for a more comprehensive assessment of possible exposure sources. Data collection for ACHS-II from 359 eligible participants took place in 2014, 7 to 9 years after ACHS.

Lessons from Toxicology: Developing a 21st-Century Paradigm for Medical Research

Biomedical developments in the 21st century provide an unprecedented opportunity to gain a dynamic systems-level and human-specific understanding of the causes and pathophysiologies of disease. This understanding is a vital need, in view of continuing failures in health research, drug discovery, and clinical translation. The full potential of advanced approaches may not be achieved within a 20th-century conceptual framework dominated by animal models. Novel technologies are being integrated into environmental health research and are also applicable to disease research, but these advances need a new medical research and drug discovery paradigm to gain maximal benefits. We suggest a new conceptual framework that repurposes the 21st-century transition underway in toxicology. Human disease should be conceived as resulting from integrated extrinsic and intrinsic causes, with research focused on modern human-specific models to understand disease pathways at multiple biological levels that are analogous to adverse outcome pathways in toxicology. Systems biology tools should be used to integrate and interpret data about disease causation and pathophysiology. Such an approach promises progress in overcoming the current roadblocks to understanding human disease and successful drug discovery and translation. A discourse should begin now to identify and consider the many challenges and questions that need to be solved.

Prepubertal Serum Concentrations of Organochlorine Pesticides and Age at Sexual Maturity in Russian Boys

BACKGROUND

Few human studies have evaluated the impact of childhood exposure to organochlorine pesticides (OCP) on pubertal development.

OBJECTIVE

We evaluated associations of serum OCP concentrations [hexachlorobenzene (HCB), β-hexachlorocyclohexane (βHCH), and p,p-dichlorodiphenyldichloroethylene (p,p´-DDE)] with age at attainment of sexual maturity among boys.

METHODS

From 2003 through 2005, 350 8- to 9-year-old boys from Chapaevsk, Russia, with measured OCPs were enrolled and followed annually for 8 years. We used multivariable interval-censored models to evaluate associations of OCPs (quartiles) with three physician-assessed measures of sexual maturity: Tanner stage 5 for genitalia growth, Tanner stage 5 for pubic hair growth, or testicular volume (TV) ≥ 20 mL in either testis.

RESULTS

In adjusted models, boys with higher HCB concentrations achieved sexual maturity reflected by TV ≥ 20 mL a mean of 3.1 months (95% CI: -1.7, 7.8), 5.3 months (95% CI: 0.6, 10.1), and 5.0 months (95% CI: 0.2, 9.8) later for quartiles Q2, Q3, and Q4, respectively, compared with Q1 (p trend = 0.04). Tanner stage 5 for genitalia growth was attained a mean of 2.2 months (95% CI: -3.1, 7.5), 5.7 months (95% CI: 0.4, 11.0), and 3.7 months (95% CI: -1.7, 9.1) later for quartiles Q2, Q3, and Q4, respectively, of βHCH compared with Q1 (p trend = 0.09). Tanner stage 5 for pubic hair growth occurred 6-9 months later on average for boys in the highest versus lowest quartile for HCB (p trend < 0.001), βHCH (trend p = 0.01), and p,p´-DDE (p trend = 0.04). No associations were observed between p,p´-DDE and Tanner stage 5 for genitalia growth or TV ≥ 20 mL.

CONCLUSIONS AND RELEVANCE

Higher prepubertal serum HCB and βHCH concentrations were associated with a later age at attainment of sexual maturity. Only the highest quartile of serum p,p´-DDE was associated with later pubic hair maturation.

CITATION

Lam T, Williams PL, Lee MM, Korrick SA, Birnbaum LS, Burns JS, Sergeyev O, Revich B, Altshul LM, Patterson DG Jr, Hauser R. 2015. Prepubertal serum concentrations of organochlorine pesticides and age at sexual maturity in Russian boys. Environ Health Perspect 123:1216-1221; http://dx.doi.org/10.1289/ehp.1409022.

My Winding Road: From Microbiology to Toxicology and Environmental Health

I would certainly never have predicted that I would become the director of the National Institute of Environmental Health Sciences (NIEHS) and the National Toxicology Program (NTP) when I was a Jewish girl growing up in Teaneck, New Jersey. My family stressed the importance of education. Yet for a girl there were many not-so-subtle suggestions that the appropriate careers were in teaching or nursing, and the most important thing was to be a wife and mother. Well, I can't disagree with the latter, although I would have to add grandmother to that list of achievements. My parents were both college graduates, but my mom only taught high school English for one year before leaving the field to start our family. My dad returned from World War II and joined his brother in accounting. After my first sister was born, my father joined my mother's family jewelry business and helped to open a second retail store. My mother helped my dad out during the busy times—Christmas and wedding season—but otherwise focused on our growing family of three girls and one boy. This became increasingly challenging when it became clear that my little brother was severely retarded and would require extra care.

Prenatal Programming and Toxicity (PPTOX) Introduction

The developmental origin of health and disease hypothesis posits that early-life exposures, including prenatal, can influence disease outcomes throughout the entire lifespan of an organism. Over the past 30 years, scientific researchers have compiled robust epidemiological and mechanistic data showing the effects of early-life nutrition, chemical exposures, and stress on prenatal programing and toxicity. Using novel techniques in genomics and epigenetics, science is now establishing strong links between low-level early-life environmental exposures and the later development of noncommunicable diseases, such as cardiovascular disease, obesity, diabetes, neurodevelopmental and neurodegenerative disease, reproductive effects, immune system function and cancer. Now scientists must engage with communities, industry, policy makers, and clinicians to leverage our newfound understanding of prenatal programing and toxicity into better health outcomes across the lifespan.

Pharmacokinetics of bisphenol A in humans following a single oral administration

BACKGROUND

Human exposures to bisphenol A (BPA) are widespread. The current study addresses uncertainties regarding human pharmacokinetics of BPA.

OBJECTIVE

To reduce uncertainties about the metabolism and excretion of BPA in humans following oral administration.

METHODS

We exposed six men and eight women to 100 μg/kg bw of deuterated BPA (d6-BPA) by oral administration and conducted blood and urine analysis over a three day period. The use of d6-BPA allowed administered d6-BPA to be distinguished from background native (unlabeled) BPA. We calculated the rate of oral absorption, serum elimination, half-life, area under the curve (AUC), urinary excretion, and metabolism to glucuronide and sulfate conjugates.

RESULTS

Mean serum total (unconjugated and conjugated) d6-BPA Cmax of 1711 nM (390 ng/ml) was observed at Tmax of 1.1 ± 0.50h. Unconjugated d6-BPA appeared in serum within 5-20 min of dosing with a mean Cmax of 6.5 nM (1.5 ng/ml) observed at Tmax of 1.3 ± 0.52 h. Detectable blood levels of unconjugated or total d6-BPA were observed at 48 h in some subjects at concentrations near the LOD (0.001-0.002 ng/ml). The half-times for terminal elimination of total d6-BPA and unconjugated d6-BPA were 6.4 ± 2.0 h and 6.2 ± 2.6h, respectively. Recovery of total administered d6-BPA in urine was 84-109%. Most subjects (10 of 14) excreted >90% as metabolites within 24h.

CONCLUSIONS

Using more sensitive methods, our study expands the findings of other human oral pharmacokinetic studies. Conjugation reactions are rapid and nearly complete with unconjugated BPA comprising less than 1% of the total d6-BPA in blood at all times. Elimination of conjugates into urine largely occurs within 24h.

Pharmacokinetics of bisphenol A in humans following a single oral administration

BACKGROUND

Human exposures to bisphenol A (BPA) are widespread. The current study addresses uncertainties regarding human pharmacokinetics of BPA.

OBJECTIVE

To reduce uncertainties about the metabolism and excretion of BPA in humans following oral administration.

METHODS

We exposed six men and eight women to 100 μg/kg bw of deuterated BPA (d6-BPA) by oral administration and conducted blood and urine analysis over a three day period. The use of d6-BPA allowed administered d6-BPA to be distinguished from background native (unlabeled) BPA. We calculated the rate of oral absorption, serum elimination, half-life, area under the curve (AUC), urinary excretion, and metabolism to glucuronide and sulfate conjugates.

RESULTS

Mean serum total (unconjugated and conjugated) d6-BPA Cmax of 1711 nM (390 ng/ml) was observed at Tmax of 1.1 ± 0.50h. Unconjugated d6-BPA appeared in serum within 5-20 min of dosing with a mean Cmax of 6.5 nM (1.5 ng/ml) observed at Tmax of 1.3 ± 0.52 h. Detectable blood levels of unconjugated or total d6-BPA were observed at 48 h in some subjects at concentrations near the LOD (0.001-0.002 ng/ml). The half-times for terminal elimination of total d6-BPA and unconjugated d6-BPA were 6.4 ± 2.0 h and 6.2 ± 2.6h, respectively. Recovery of total administered d6-BPA in urine was 84-109%. Most subjects (10 of 14) excreted >90% as metabolites within 24h.

CONCLUSIONS

Using more sensitive methods, our study expands the findings of other human oral pharmacokinetic studies. Conjugation reactions are rapid and nearly complete with unconjugated BPA comprising less than 1% of the total d6-BPA in blood at all times. Elimination of conjugates into urine largely occurs within 24h.

Estimation of tetrabromobisphenol A (TBBPA) percutaneous uptake in humans using the parallelogram method

Tetrabromobisphenol A (TBBPA) is currently the world's highest production volume brominated flame retardant. Humans are frequently exposed to TBBPA by the dermal route. In the present study, a parallelogram approach was used to make predictions of internal dose in exposed humans. Human and rat skin samples received 100 nmol of TBBPA/cm(2) skin and absorption and penetrance were determined using a flow-through in vitro system. TBBPA-derived [(14)C]-radioactivity was determined at 6h intervals in the media and at 24h post-dosing in the skin. The human skin and media contained an average of 3.4% and 0.2% of the total dose at the terminal time point, respectively, while the rat skin and media contained 9.3% and 3.5%, respectively. In the intact rat, 14% of a dermally-administered dose of ~100 nmol/cm(2) remained in the skin at the dosing site, with an additional 8% reaching systemic circulation by 24h post-dosing. Relative absorption and penetrance were less (10% total) at 24h following dermal administration of a ten-fold higher dose (~1000 nmol/cm(2)) to rats. However, by 72 h, 70% of this dose was either absorbed into the dosing-site skin or had reached systemic circulation. It is clear from these results that TBBPA can be absorbed by the skin and dermal contact with TBBPA may represent a small but important route of exposure. Together, these in vitro data in human and rat skin and in vivo data from rats may be used to predict TBBPA absorption in humans following dermal exposure. Based on this parallelogram calculation, up to 6% of dermally applied TBBPA may be bioavailable to humans exposed to TBBPA.

Timing of Environmental Exposures as a Critical Element in Breast Cancer Risk

OBJECTIVE

The role of the chemical environment in disease initiation or progression is becoming more evident. Endocrine disruption via environmental chemicals is now well documented in humans, rodent research models, and wildlife. Breast cancer is an endocrine-based disease whose risk may be modified by environmental exposures. Our purpose is to encourage more investigation into early life environmental exposures as they relate to breast cancer risk factors and disease over a lifetime.

EVIDENCE

The 2009 President's Cancer Panel, 2012 Institute of Medicine, 2013 Interagency Breast Cancer and the Environment Research Coordinating Committee reports, and research publications dated ≥2012 in PubMed were used to inform our perspective.

CONSENSUS PROCESS

Literature was reviewed and evidence gathered on the effects of the environment on risk of breast cancer or mammary tumor development in animal research models as it pertained to the influence of timing of exposure on later-life outcomes.

CONCLUSIONS

Evidence has accumulated for several chemicals that environmental factors have a stronger effect on breast cancer risk when exposure occurred early in life. The insecticide, dichlorodiphenyltrichloroethane, is an excellent example and is just one of several chemicals for which there seems to be both animal and human evidence for the developmental basis of adult disease. The developing breast undergoes many changes in early life, leaving it vulnerable to the effects of epigenetic marks, endocrine disruption, and carcinogens. More research is needed in the area of early beginnings of breast cancer, with prevention of the disease as the ultimate goal.

IARC monographs: 40 years of evaluating carcinogenic hazards to humans

BACKGROUND

Recently, the International Agency for Research on Cancer (IARC) Programme for the Evaluation of Carcinogenic Risks to Humans has been criticized for several of its evaluations, and also for the approach used to perform these evaluations. Some critics have claimed that failures of IARC Working Groups to recognize study weaknesses and biases of Working Group members have led to inappropriate classification of a number of agents as carcinogenic to humans.

OBJECTIVES

The authors of this Commentary are scientists from various disciplines relevant to the identification and hazard evaluation of human carcinogens. We examined criticisms of the IARC classification process to determine the validity of these concerns. Here, we present the results of that examination, review the history of IARC evaluations, and describe how the IARC evaluations are performed.

DISCUSSION

We concluded that these recent criticisms are unconvincing. The procedures employed by IARC to assemble Working Groups of scientists from the various disciplines and the techniques followed to review the literature and perform hazard assessment of various agents provide a balanced evaluation and an appropriate indication of the weight of the evidence. Some disagreement by individual scientists to some evaluations is not evidence of process failure. The review process has been modified over time and will undoubtedly be altered in the future to improve the process. Any process can in theory be improved, and we would support continued review and improvement of the IARC processes. This does not mean, however, that the current procedures are flawed.

CONCLUSIONS

The IARC Monographs have made, and continue to make, major contributions to the scientific underpinning for societal actions to improve the public's health.

Gene-environment interplay in common complex diseases: forging an integrative model—recommendations from an NIH workshop

Although it is recognized that many common complex diseases are a result of multiple genetic and environmental risk factors, studies of gene-environment interaction remain a challenge and have had limited success to date. Given the current state-of-the-science, NIH sought input on ways to accelerate investigations of gene-environment interplay in health and disease by inviting experts from a variety of disciplines to give advice about the future direction of gene-environment interaction studies. Participants of the NIH Gene-Environment Interplay Workshop agreed that there is a need for continued emphasis on studies of the interplay between genetic and environmental factors in disease and that studies need to be designed around a multifaceted approach to reflect differences in diseases, exposure attributes, and pertinent stages of human development. The participants indicated that both targeted and agnostic approaches have strengths and weaknesses for evaluating main effects of genetic and environmental factors and their interactions. The unique perspectives represented at the workshop allowed the exploration of diverse study designs and analytical strategies, and conveyed the need for an interdisciplinary approach including data sharing, and data harmonization to fully explore gene-environment interactions. Further, participants also emphasized the continued need for high-quality measures of environmental exposures and new genomic technologies in ongoing and new studies.