Drinking water chlorination and adverse birth outcomes in Taiwan

Using simple and easy water quality parameters to predict trihalomethane occurrence in tap water

Monitoring of disinfection by-products (DBPs) in water supply system is important to ensure safety of drinking water. Yet it is a laborious job. Developing predictive DBPs models using simple and easy parameters is a promising way. Yet current models could not be well applied into practice because of the improper dataset (e.g. not from real tap water) they used or involving the parameters that are difficult to measure or require expensive instruments. In this study, four simple and easy water quality parameters (temperature, pH, UVA₂₅₄ and Cl₂) were used to predict trihalomethane (THMs) occurrence in tap water. Linear/log linear regression models (LRM) and radial basis function artificial neural network (RBF ANN) were adopted to develop the THMs models. 64 observations from tap water samples were used to develop and test models. Results showed that only one or two parameters entered LRMs, and their prediction ability was very limited (testing datasets: N₂₅ = 46-69%, r_p = 0.334-0.459). Different from LRM, the prediction accuracy of RBF ANNs developed with pH, temperature, UVA₂₅₄ and Cl₂ can be improved continuously by tweaking the maximum number of neuron (MN) and Gaussian function spread (S) until it reached best. The optimum RBF ANNs of T-THMs, TCM and BDCM were obtained when setting MN = 20, S = 100, 100.1 and 60, respectively, where the N₂₅ and r_p values for testing datasets reached 85-92% and 0.813-0.886, respectively. Accurate predictions of THMs by RBF ANNs with these four simple and easy parameters paved an economic and convenient way for THMs monitoring in real water supply system.

Urinary biomarker of late pregnancy exposure to drinking water disinfection by-products and ultrasound measures of fetal growth in Wuhan, China

BACKGROUND

Disinfection by-products (DBPs) have been shown to be reproductive and developmental toxicity. However, few studies examine the effect of prenatal exposure to DBPs on fetal growth via ultrasound measures.

OBJECTIVE

To investigate the associations between maternal exposure to DBPs during late pregnancy and ultrasound measures of fetal growth.

METHODS

We included 332 pregnant women who presented to a hospital to wait for delivery in Wuhan, China. Ultrasound parameters of fetal growth including femur length (FL), head circumference (HC), abdominal circumference (AC) and biparietal diameter (BPD) were assessed. We measured maternal TCAA concentrations in first morning urine collected from late pregnancy as a biomarker of in utero DBP exposure levels. Multivariable linear regression models were used to examine the associations between maternal urinary TCAA concentrations during late pregnancy and ultrasound parameters of fetal growth.

RESULTS

We found that elevated maternal creatinine (Cr)-adjusted urinary TCAA levels had negative associations with BPD, HC and FL in boys but not in girls (P interaction = 0.04, 0.05 and 0.08, respectively). Male fetal BPD, HC and FL had decreases of 0.21 cm (95% CI: -0.35, -0.07; P for trend = 0.003), 0.46 cm (95% CI: -0.81, -0.10; P for trend = 0.01) and 0.17 cm (95% CI: -0.30, -0.04; P for trend = 0.01) for the highest vs. lowest tertile of Cr-adjusted urinary TCAA, respectively. These negative associations persisted for maternal Cr-adjusted urinary TCAA concentrations modeled as continuous variables.

CONCLUSION

The results from our study suggest that maternal exposure to TCAA during late pregnancy may have adverse effects on male fetal growth.

Occurrence of regulated and emerging iodinated DBPs in the Shanghai drinking water

Drinking water chlorination plays a pivotal role in preventing pathogen contamination against water-borne disease. However, chemical disinfection leads to the formation of halogenated disinfection by products (DBPs). Many DBPs are highly toxic and are of health concern. In this study, we conducted a comprehensive measurements of DBPs, including iodoacetic acid (IAA), iodoform (IF), nine haloacetic acids and four trihalomethanes in drinking waters from 13 water plants in Shanghai, China. The results suggested that IAA and IF were found in all the water treatment plants, with maximum levels of 1.66 µg/L and 1.25 µg/L for IAA and IF, respectively. Owing to deterioration of water quality, the Huangpu River has higher IAA and IF than the Yangtze River. Our results also demonstrated that low pH, high natural organic matter, ammonia nitrogen, and iodide in source waters increased IAA and IF formation. Compared to chlorine, chloramines resulted in higher concentration of iodinated DBP, but reduced the levels of trihalomethanes. This is the first study to reveal the widespread occurrence of IAA and IF in drinking water in China. The data provide a better understanding on the formation of iodinated disinfection byproducts and the findings should be useful for treatment process improvement and disinfection byproducts controls.

Environmental contaminant exposures and preterm birth: a comprehensive review

Preterm birth is a significant public health concern, as it is associated with high risk of infant mortality, various morbidities in both the neonatal period and later in life, and a significant societal economic burden. As many cases are of unknown etiology, identification of the contribution of environmental contaminant exposures is a priority in the study of preterm birth. This is a comprehensive review of all known studies published from 1992 through August 2012 linking maternal exposure to environmental chemicals during pregnancy with preterm birth. Using PubMed searches, studies were identified that examined associations between preterm birth and exposure to five categories of environmental toxicants, including persistent organic pollutants, drinking-water contaminants, atmospheric pollutants, metals and metalloids, and other environmental contaminants. Individual studies were summarized and specific suggestions were made for future work in regard to exposure and outcome assessment methods as well as study design, with the recommendation of focusing on potential mediating toxicological mechanisms. In conclusion, no consistent evidence was found for positive associations between individual chemical exposures and preterm birth. By identifying limitations and addressing the gaps that may have impeded the ability to identify true associations thus far, this review can guide future epidemiologic studies of environmental exposures and preterm birth.

Environmental and urinary markers of prenatal exposure to drinking water disinfection by-products, fetal growth, and duration of gestation in the PELAGIE birth cohort (Brittany, France, 2002-2006)

Although prenatal exposure to water disinfection by-products does not appear to affect the duration of gestation, its impact on fetal growth remains an open question. The authors studied the associations between prenatal exposure to disinfection by-products and fetal growth restriction (FGR) and preterm birth in the PELAGIE cohort, a French birth cohort comprising 3,421 pregnant women recruited between 2002 and 2006. Exposure was assessed by estimating levels of trihalomethanes (THMs) in tap water during pregnancy and maternal water use and by measuring maternal urinary levels of trichloroacetic acid (TCAA) during early pregnancy in a nested case-control design that compared 174 FGR cases, 114 preterm births, and 399 controls. Higher uptake of THMs (especially brominated THMs) was associated with a higher risk of FGR. Women with TCAA detected in their urine (>0.01 mg/L) had a higher risk of FGR than those with TCAA levels below the detection limit (adjusted odds ratio = 1.8, 95% confidence interval: 0.9, 3.7) and had an odds ratio for preterm birth below 1 (adjusted odds ratio = 0.8, 95% confidence interval: 0.3, 2.6). Results from this prospective study, the first to use a biomarker of disinfection by-product exposure, suggest that prenatal exposure affects fetal growth, but the causal agent or agents remain to be identified.

Decreased birth weight in relation to maternal urinary trichloroacetic acid levels

BACKGROUND

The effect of exposure to disinfection by-products (DBPs) during pregnancy on newborn's birth weight has been commonly described in animal studies. However, epidemiological evidence was not consistent.

OBJECTIVES

To investigate the relationship between exposure to DBPs and newborn's birth weight in a Chinese population, we conducted a cross-sectional study in Wuhan, China.

METHODS

A total number of 398 women who had given birth to a live singleton with a gestational age between 37 to 42 weeks were recruited from a local hospital between November 2008 and May 2009. Basic information for all mothers and newborns was obtained from clinic birth records. Among these subjects, 180 women also gave further information including maternal medical history, social status and water-use behaviors by a face-to-face interview. Urinary creatinine (Cr) adjusted trichloroacetic (TCAA) was used as an exposure biomarker.

RESULTS

No statically significant results were found in the linear regression for both 398 participants and 180 participants who finished questionnaires. However, both the crude and adjusted results showed that the mean birth weight of the subjects in the third and top quartiles of Cr-adjusted urinary TCAA concentrations was decreased compared with those in the lowest quartile. Subjects in the top quartiles had the lowest mean birth weight compared to those in other quartiles. In addition, a weak correlation was observed among 82 subjects between drinking water ingestion and urinary Cr-adjusted TCAA (r=0.23, P=0.04).

CONCLUSION

Our findings suggested that elevated exposure to DBPs may affect fetal growth. The effect of exposure to DBPs during pregnancy on birth weight still warrants further investigations.

The impact of different causal models on estimated effects of disinfection by-products on preterm birth

BACKGROUND

Previous epidemiologic studies of preterm birth and drinking water disinfection by-products (DBP) reported inconsistent results especially for third trimester exposures. These inconsistencies may have been due to differences in the underlying causal model assumed and methodological issues, including the method of analysis (cumulative vs. density-sampling of controls and matching on gestational age) and appropriate control of confounding.

METHODS

We use data from previously published research to illustrate how different causal models, methods of analysis, and the choice of covariates to control impact results.

RESULTS

Exposure at high measured TTHM levels (≥ 60 μg/l) during the last trimester - with cumulatively sampled controls - corresponded to negative effect estimates when comparing preterm to term births and averaging exposure over different length periods. In contrast, density-sampling of controls with an exposure truncated at 36 weeks gestation and adjustment for possible confounding by exposures experienced in prior trimesters led to moderate changes in risk at the highest level of exposure averaged over the four weeks prior to birth.

CONCLUSIONS

We recommend that future research on an exposure to DBPs and risk of preterm birth explore the sensitivity of their findings to different model specifications, specifically: (1) cumulative vs. density-sampling of controls when evaluating third trimester or whole pregnancy exposures, taking into account exposure-averaging length; (2) short-term peak exposures vs. long-term exposures; and (3) adjustment for exposure during prior pregnancy periods when evaluating later trimester exposures to account for possible 'priming' effects of early exposures.

Traffic air pollution and risk of death from gastric cancer in Taiwan: petrol station density as an indicator of air pollutant exposure

To investigate the relationship between air pollution and risk of death attributed to gastric cancer, a matched cancer case-control study was conducted using deaths that occurred in Taiwan from 2004 through 2008. Data for all eligible gastric cancer deaths were obtained and compared to a control group consisting of individuals who died from causes other than neoplasms and diseases that were associated with gastrointestinal (GIT) disorders. The controls were pair-matched to the cancer cases by gender, year of birth, and year of death. Each matched control was randomly selected from the set of possible controls for each cancer case. Data for the number of petrol stations in study municipalities were collected from two major petroleum supply companies. The petrol station density (per square kilometer) (PSD) for study municipalities was used as an indicator of a subject's exposure to benzene and other hydrocarbons present in ambient evaporative losses of petrol or to air emissions from motor vehicles. The exposed individuals were subdivided into three categories (≤25th percentile; 25th-75th percentile; >75th percentile) according to PSD in the residential municipality. Results showed that individuals who resided in municipalities with the highest PSD were at an increased risk of death attributed to gastric cancer compared to those subjects living in municipalities with the lowest PSD. The findings of this study warrant further investigation of the role of traffic air pollution exposure in the etiology of gastric cancer.

Traffic air pollution and risk of death from bladder cancer in Taiwan using petrol station density as a pollutant indicator

To investigate the relationship between air pollution and risk of death from bladder cancer, a matched cancer case-control study was conducted using deaths that occurred in Taiwan from 1997 through 2006. Data for all eligible bladder cancer deaths were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. The control group consisted of individuals who died from causes other than cancer or diseases associated with genitourinary problems. The controls were pair matched to the cases by gender, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each case. Data for the number of petrol stations in study municipalities were collected from the two major petroleum supply companies, Chinese Petroleum Corporation (CPC) and Formosa Petrochemical Corporation (FPCC). The petrol station density (per square kilometer) (PSD) for study municipalities was used as an indicator of a subject's exposure to benzene and other hydrocarbons present in ambient evaporative losses of petrol or to air emissions from motor vehicles. The subjects were divided into tertiles according to PSD in their residential municipality. The present study showed that individuals who resided in municipalities with high PSD levels were at an increased risk of death from bladder cancer compared to subjects living in municipalities with a low PSD level; however, the differences are not statistically significant. The findings of this study warrant further investigation of the role of vehicular air pollutant emissions in the etiology of bladder cancer development.

The epidemiology and possible mechanisms of disinfection by-products in drinking water

This paper summarizes the epidemiological evidence for adverse health effects associated with disinfection by-products (DBPs) in drinking water and describes the potential mechanism of action. There appears to be good epidemiological evidence for a relationship between exposure to DBPs, as measured by trihalomethanes (THMs), in drinking water and bladder cancer, but the evidence for other cancers including colorectal cancer is inconclusive and inconsistent. There appears to be some evidence for an association between exposure to DBPs, specifically THMs, and little for gestational age/intrauterine growth retardation and, to a lesser extent, pre-term delivery, but evidence for relationships with other outcomes such as low birth weight, stillbirth, congenital anomalies and semen quality is inconclusive and inconsistent. Major limitations in exposure assessment, small sample sizes and potential biases may account for the inconclusive and inconsistent results in epidemiological studies. Moreover, most studies have focused on total THMs as the exposure metric, whereas other DBPs appear to be more toxic than the THMs, albeit generally occurring at lower levels in the water. The mechanisms through which DBPs may cause adverse health effects including cancer and adverse reproductive effects have not been well investigated. Several mechanisms have been suggested, including genotoxicity, oxidative stress, disruption of folate metabolism, disruption of the synthesis and/or secretion of placental syncytiotrophoblast-derived chorionic gonadotropin and lowering of testosterone levels, but further work is required in this area.

Drinking-water herbicide exposure in Indiana and prevalence of small-for-gestational-age and preterm delivery

BACKGROUND

Atrazine and other corn herbicides are routinely detected in drinking water. Two studies on potential association of atrazine with small-for-gestational-age (SGA) and preterm birth prevalence found inconsistent results. Moreover, these studies did not control for individual-level potential confounders.

OBJECTIVES

Our retrospective cohort study evaluated whether atrazine in drinking water is associated with increased prevalence of SGA and preterm birth.

METHODS

We developed atrazine concentration time series for 19 water systems in Indiana from 1993 to 2007 and selected all births (n = 24,154) based on geocoded mother's residences. Log-binomial models were used to estimate prevalence ratios (PRs) for SGA and preterm delivery in relation to atrazine concentrations during various periods of the pregnancy. Models controlled for maternal demographic characteristics, prenatal care and reproductive history, and behavioral risk factors (smoking, drinking, drug use).

RESULTS

Atrazine in drinking water during the third trimester and the entire pregnancy was associated with a significant increase in the prevalence of SGA. Atrazine in drinking water > 0.1 microg/L during the third trimester resulted in a 17-19% increase in the prevalence of SGA compared with the control group (< 0.1 microg/L). Mean atrazine concentrations over the entire pregnancy > 0.644 microg/L were associated with higher SGA prevalence than in the control group (adjusted PR = 1.14; 95% confidence interval, 1.03-1.24). No significant association was found for preterm delivery.

CONCLUSIONS

We found that atrazine, and perhaps other co-occurring herbicides in drinking water, is associated with an increased prevalence of SGA, but not preterm delivery.

Ambient exposure to criteria air pollutants and risk of death from bladder cancer in Taiwan

To investigate the relationship between air pollution and risk of death from bladder cancer, the authors conducted a matched case-control study using deaths that occurred in Taiwan from 1995 through 2005. Data on all eligible bladder cancer deaths were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. The control group consisted of people who died from causes other than cancer or diseases associated with genitourinary problems. The controls were pair matched to the cases by sex, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each case. Classification of exposure to municipality air pollution was based on the measured levels of nitrogen dioxide and sulfur dioxide. The results of the present study show that there is a significant positive association between the levels of air pollution and bladder cancer mortality. The adjusted odds ratios (95% confidence interval) were 1.37 (1.03-1.82) for the group with medium air pollution level and 1.98 (1.36-2.88) for the group with high air pollution level when compared to the group with the low air pollution level. Trend analyses showed statistically significant trend in risk of death from bladder cancer with increasing air pollution level. The findings of this study warrant further investigation of the role of air pollutants in the etiology of bladder cancer.

Association of bladder cancer with residential exposure to petrochemical air pollutant emissions in Taiwan

To investigate the relationship between petrochemical air pollution and risk of death due to bladder cancer, studies were conducted using a matched cancer case-control model based upon deaths that occurred in Taiwan from 1995 through 2005. Data on all eligible bladder cancer deaths were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. The control group consisted of individuals who died from causes other than neoplasms or diseases associated with genitourinary problems. The controls were pair matched to the cases by gender, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each case. The proportion of a municipality's total population employed in the petrochemical industry in a municipality was used as an indicator of a resident's exposure to air emissions from the petrochemical industry. The subjects were divided into three levels (< or =25th percentile; 25th-50th percentile; >50th percentile). Subjects who lived in the group of municipalities characterized by the high levels of petrochemical air pollution had a significantly higher risk of death attributed to bladder cancer than subjects in the group that lived in municipalities with the lowest petrochemical air pollution levels, after controlling for possible confounders. The findings of this study warrant further investigation of the role of petrochemical air pollution in the etiology of bladder cancer.

Degradation of DBPs' precursors in river water before and after slow sand filtration by photo-Fenton process at pH 5 in a solar CPC reactor

The generation of disinfection by-products during water treatment can be controlled by reducing the levels of precursor species prior to the chlorination step. The Natural Organic Matter (NOM) is the principal organic precursor and conventional removal of pollutants such as coagulation, flocculation and filtration do not guarantee the total NOM removal. In this study the degradation of NOM model compounds (dihydroxy-benzene) as well as the removal of NOM from river water via photo-Fenton process in a CPC solar photo-reactor is presented. The effect of solar activated photo-Fenton reagent at pH 5.0 before and after a slow sand filtration (SSF) in waters containing natural iron species is investigated and the details reported. The results showed that the total transformation of dihydroxy-benzene compounds along a mineralization higher than 80% was obtained. The mineralization of the organic compounds dissolved in natural water was higher than in Milli-Q water, suggesting that the aqueous organic and inorganic components (metals, humic acids and photoactive species) positively affect the photocatalytic process. When 1.0mg/L of Fe(3+) is added to the system, the photo-Fenton degradation was improved. Therefore the photo-Fenton reagent could be an interesting complement to other processes for NOM removal. Comparing the response of two rivers as media for the organic compounds degradation it was observed that the NOM photo-degradation rate depends of the water composition.

Epidemiologic evidence of relationships between reproductive and child health outcomes and environmental chemical contaminants

This review summarizes the level of epidemiologic evidence for relationships between prenatal and/or early life exposure to environmental chemical contaminants and fetal, child, and adult health. Discussion focuses on fetal loss, intrauterine growth restriction, preterm birth, birth defects, respiratory and other childhood diseases, neuropsychological deficits, premature or delayed sexual maturation, and certain adult cancers linked to fetal or childhood exposures. Environmental exposures considered here include chemical toxicants in air, water, soil/house dust and foods (including human breast milk), and consumer products. Reports reviewed here included original epidemiologic studies (with at least basic descriptions of methods and results), literature reviews, expert group reports, meta-analyses, and pooled analyses. Levels of evidence for causal relationships were categorized as sufficient, limited, or inadequate according to predefined criteria. There was sufficient epidemiological evidence for causal relationships between several adverse pregnancy or child health outcomes and prenatal or childhood exposure to environmental chemical contaminants. These included prenatal high-level methylmercury (CH(3)Hg) exposure (delayed developmental milestones and cognitive, motor, auditory, and visual deficits), high-level prenatal exposure to polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs), and related toxicants (neonatal tooth abnormalities, cognitive and motor deficits), maternal active smoking (delayed conception, preterm birth, fetal growth deficit [FGD] and sudden infant death syndrome [SIDS]) and prenatal environmental tobacco smoke (ETS) exposure (preterm birth), low-level childhood lead exposure (cognitive deficits and renal tubular damage), high-level childhood CH(3)Hg exposure (visual deficits), high-level childhood exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (chloracne), childhood ETS exposure (SIDS, new-onset asthma, increased asthma severity, lung and middle ear infections, and adult breast and lung cancer), childhood exposure to biomass smoke (lung infections), and childhood exposure to outdoor air pollutants (increased asthma severity). Evidence for some proven relationships came from investigation of relatively small numbers of children with high-dose prenatal or early childhood exposures, e.g., CH(3)Hg poisoning episodes in Japan and Iraq. In contrast, consensus on a causal relationship between incident asthma and ETS exposure came only recently after many studies and prolonged debate. There were many relationships supported by limited epidemiologic evidence, ranging from several studies with fairly consistent findings and evidence of dose-response relationships to those where 20 or more studies provided inconsistent or otherwise less than convincing evidence of an association. The latter included childhood cancer and parental or childhood exposures to pesticides. In most cases, relationships supported by inadequate epidemiologic evidence reflect scarcity of evidence as opposed to strong evidence of no effect. This summary points to three main needs: (1) Where relationships between child health and environmental exposures are supported by sufficient evidence of causal relationships, there is a need for (a) policies and programs to minimize population exposures and (b) population-based biomonitoring to track exposure levels, i.e., through ongoing or periodic surveys with measurements of contaminant levels in blood, urine and other samples. (2) For relationships supported by limited evidence, there is a need for targeted research and policy options ranging from ongoing evaluation of evidence to proactive actions. (3) There is a great need for population-based, multidisciplinary and collaborative research on the many relationships supported by inadequate evidence, as these represent major knowledge gaps. Expert groups faced with evaluating epidemiologic evidence of potential causal relationships repeatedly encounter problems in summarizing the available data. A major driver for undertaking such summaries is the need to compensate for the limited sample sizes of individual epidemiologic studies. Sample size limitations are major obstacles to exploration of prenatal, paternal, and childhood exposures during specific time windows, exposure intensity, exposure-exposure or exposure-gene interactions, and relatively rare health outcomes such as childhood cancer. Such research needs call for investments in research infrastructure, including human resources and methods development (standardized protocols, biomarker research, validated exposure metrics, reference analytic laboratories). These are needed to generate research findings that can be compared and subjected to pooled analyses aimed at knowledge synthesis.

Estimated effects of disinfection by-products on preterm birth in a population served by a single water utility

OBJECTIVES

We evaluated the association between drinking-water disinfection by-products and preterm births using improved exposure assessment and more appropriate analysis methods than used in prior studies.

METHODS

During 1999-2001, vital record data were obtained for a large, racially diverse population residing in 27 Massachusetts communities that received drinking water from a single public utility. This water system was monitored weekly for total trihalomethanes (TTHM), and it maintained geographically stable total TTHM levels system-wide during the study period. We employed proportional hazards regression to examine the effects of trimester-specific and shorter-term peak exposures to TTHM in drinking water late in pregnancy on preterm births in 37,498 singletons.

RESULTS

For all women, our data suggested no more than a small increase, if any, in risk for delivering a preterm baby when exposed to > or = 60 microg/L TTHM during the 4 weeks before birth [hazard ratio (HR) = 1.13; 95% confidence interval (CI), 0.95-1.35]. However, women who depended on a governmental source of payment for prenatal care were at increased risk when exposed at such levels late in gestation (HR = 1.39; 95% CI, 1.06-1.81). In contrast, exposure to high levels of TTHM during the second trimester and high exposure throughout pregnancy resulted in a 15-18% reduction in risk for preterm delivery in our population.

CONCLUSIONS

This finding confirms previous reports of a negative association during the second trimester. Our data also suggested a possible positive association with shorter-term third-trimester TTHM exposure in mothers of lower socioeconomic status.

Estimated effects of disinfection by-products on birth weight in a population served by a single water utility

Research has suggested that trihalomethane exposures during pregnancy might impair fetal growth. Most epidemiologic studies, however, relied on relatively crude exposure assessment methods and did not examine racial/ethnic subgroups. During 1999-2001, vital records data were obtained for a large, racially diverse population residing in 27 Massachusetts communities that received drinking water from a single public utility. The water system was monitored weekly for trihalomethanes and, system-wide, it maintained geographically stable total trihalomethane levels during the study period. The authors examined the effects of trimester-specific and pregnancy average exposures to total trihalomethane in drinking water on term low birth weight in all singleton births. A high average total trihalomethane exposure (> or = 70 microg/liter) during the second trimester increased the risk of term low birth weight (odds ratio = 1.50, 95% confidence interval (CI): 1.07, 2.10). The estimated risk increase for Caucasians during the second trimester was 37% (95% CI: 0.80, 2.36), while for all minority women combined (i.e., African Americans, Hispanics, and Asians) it was 60% (95% CI: 1.03, 2.47). The study data suggest that high levels (> or = 70 microg/liter) of trihalomethanes experienced during the second trimester and pregnancy overall may affect fetal growth.