Residential proximity to agricultural fumigant use and respiratory health in 7-year old children.

OBJECTIVES: To examine the relationship between residential proximity to agricultural fumigant use and respiratory symptoms and lung function in 7-year old children. METHODS: Participants were 294 children living in the agricultural Salinas Valley, California and enrolled in the Center for the Health Assessment of Mothers and Children Of Salinas (CHAMACOS) study. We obtained information on respiratory symptoms and asthma medication use from maternal questionnaires and children performed spirometry to determine the forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and forced expiratory flow 25-75% (FEF25-75) at 7-years of age. We estimated agricultural fumigant use within 3, 5 and 8 km of residences during pregnancy and from birth to age 7 using California's Pesticide Use Report data. We evaluated the association between prenatal and postnatal residential proximity to agricultural use of methyl bromide, chloropicrin, metam sodium and 1,3-dichloropropene with respiratory symptoms and use of asthma medication with logistic regression models and continuous lung function measurements with linear regression models adjusted for confounders. RESULTS: There were no significant associations between residential proximity to use of fumigants and respiratory symptoms or use of asthma medication. We did not observe any adverse relationships between residential proximity to fumigant use and lung function measurements. Unexpectedly, we observed suggestive evidence of improved FEV1 and FEF25-75 with higher use of methyl bromide and chloropicrin during the prenatal period. For example, for each 10-fold increase in methyl bromide use during the prenatal development period we observed higher FEV1 (ß = 0.06 L/s; 95% CI: 0.00, 0.12) and higher FEF25-75 (ß = 0.15 L/s; 95% CI: 0.03, 0.27). Maternal report of child allergies (runny nose without a cold during the previous year) modified the relationship between FEV1 and prenatal proximity to methyl bromide use (p = .07) and we only observed higher FEV1 among children without allergies (ß = 0.08 L/s; 95% CI: 0.02, 0.14 for a 10-fold increase in methyl bromide use during the prenatal period). CONCLUSIONS: Residential proximity to agricultural fumigant use during pregnancy and childhood did not adversely affect respiratory health in the children through 7 years of age. These findings should be explored in larger studies.

Residential proximity to agricultural fumigant use and IQ, attention and hyperactivity in 7-year old children.

OBJECTIVES: Our objective was to examine the relationship between residential proximity to agricultural fumigant use and neurodevelopment in 7-year old children. METHODS: Participants were living in the agricultural Salinas Valley, California and enrolled in the Center for the Health Assessment of Mothers and Children Of Salinas (CHAMACOS) study. We administered the Wechsler Intelligence Scale for Children (4th Edition) to assess cognition and the Behavioral Assessment System for Children (2nd Edition) to assess behavior. We estimated agricultural fumigant use within 3, 5 and 8km of residences during pregnancy and from birth to age 7 using California's Pesticide Use Report data. We evaluated the association between prenatal (n = 285) and postnatal (n = 255) residential proximity to agricultural use of methyl bromide, chloropicrin, metam sodium and 1,3-dichloropropene with neurodevelopment. RESULTS: We observed decreases of 2.6 points (95% Confidence Interval (CI): -5.2, 0.0) and 2.4 points (95% CI: -4.7, -0.2) in Full-Scale intelligence quotient for each ten-fold increase in methyl bromide and chloropicrin use within 8km of the child's residences from birth to 7-years of age, respectively. There were no associations between residential proximity to use of other fumigants and cognition or proximity to use of any fumigant and hyperactivity or attention problems. These findings should be explored in larger studies.

In utero and childhood DDT, DDE, PBDE and PCBs exposure and sex hormones in adolescent boys: The CHAMACOS study.

Dichlorodiphenyltrichloroethane (DDT), polybrominated diphenyl ether (PBDE) flame retardants, and polychlorinated biphenyls (PCBs) are believed to be endocrine-disrupting chemicals (EDCs) in humans and animals. The purpose of this study is to examine the relationship of in utero and childhood exposure to these purported EDCs and reproductive hormones in adolescent boys who participated in CHAMACOS, an ongoing birth cohort in California's Salinas Valley. We measured o,p'- and p,p'-DDT, p,p'-DDE, PBDEs and PCBs in serum collected from mothers during pregnancy or at delivery and from their sons at 9 years. We measured concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and total testosterone (T) from 234 of their sons at 12 years. In adjusted models, we found that a 10-fold increase in maternal prenatal serum concentrations of BDE-153 was associated with a 22.2% increase (95% CI: 1.0, 47.9) in FSH, a 96.6% increase (95% CI: 35.7, 184.7) in LH, and a 92.4% increase (95% CI: 20.9, 206.2) increase in T. Similarly, BDE-100 concentrations were associated with increases in boys' LH levels. A 10-fold increase in total prenatal ΣPCBs was associated with a 64.5% increase (95% CI: 8.6, 149.0) in FSH, primarily driven by non- dioxin-like congeners. Boys' hormone levels were only marginally associated with prenatal DDT or DDE in primary models, but when boys' Tanner stage at age 12 was added to models, prenatal maternal DDT levels were associated with decreases in LH (adjusted percent change per 10-fold increase=-18.5%, 95% CI: -29.8, -5.4) and T (percent change=-18.2%, 95% CI: -30.2, -4.2) and DDE with LH (percent change=-18.3%, 95% CI: -32.9, -0.6). Exposures measured in the children's serum at 9 years also showed associations between BDE-153 and ΣPCBs. However, there is evidence that these associations appear to be mediated by child BMI. This study suggests associations on male hormones of 12year old boys related to exposure to certain EDC exposure prenatally. The implications on future reproductive function in puberty and adulthood should be determined.

Prenatal Organophosphorus Pesticide Exposure and Child Neurodevelopment at 24 Months: An Analysis of Four Birth Cohorts.

BACKGROUND: Organophosphorus pesticides (OPs) are used in agriculture worldwide. Residential use was common in the United States before 2001. OBJECTIVES: We conducted a pooled analysis of four birth cohorts (children's centers; n = 936) to evaluate associations of prenatal exposure to OPs with child development at 24 months. METHODS: Using general linear models, we computed site-specific and pooled estimates of the association of total dialkyl (ΣDAP), diethyl (ΣDEP), and dimethylphosphate (ΣDMP) metabolite concentrations in maternal prenatal urine with mental and psychomotor development indices (MDI/PDI) and evaluated heterogeneity by children's center, race/ethnicity, and PON1 genotype. RESULTS: There was significant heterogeneity in the center-specific estimates of association for ΣDAP and ΣDMP and the MDI (p = 0.09, and p = 0.05, respectively), as well as heterogeneity in the race/ethnicity-specific estimates for ΣDAP (p = 0.06) and ΣDMP (p = 0.02) and the MDI. Strong MDI associations in the CHAMACOS population per 10-fold increase in ΣDAP (ß = -4.17; 95% CI: -7.00, -1.33) and ΣDMP (ß = -3.64; 95% CI: -5.97, -1.32) were influential, as were associations among Hispanics (ß per 10-fold increase in ΣDAP = -2.91; 95% CI: -4.71, -1.12). We generally found stronger negative associations of ΣDAP and ΣDEP with the 24-month MDI for carriers of the 192Q PON1 allele, particularly among blacks and Hispanics. CONCLUSIONS: Data pooling was complicated by center-related differences in subject characteristics, eligibility, and changes in regulations governing residential use of OPs during the study periods. Pooled summary estimates of prenatal exposure to OPs and neurodevelopment should be interpreted with caution because of significant heterogeneity in associations by center, race/ethnicity, and PON1 genotype. Subgroups with unique exposure profiles or susceptibilities may be at higher risk for adverse neurodevelopment following prenatal exposure. CITATION: Engel SM, Bradman A, Wolff MS, Rauh VA, Harley KG, Yang JH, Hoepner LA, Barr DB, Yolton K, Vedar MG, Xu Y, Hornung RW, Wetmur JG, Chen J, Holland NT, Perera FP, Whyatt RM, Lanphear BP, Eskenazi B. 2016. Prenatal organophosphorus pesticide exposure and child neurodevelopment at 24 months: an analysis of four birth cohorts. Environ Health Perspect 124:822-830; http://dx.doi.org/10.1289/ehp.1409474.

Prenatal Exposure to Organophosphorous Pesticides and Fetal Growth: Pooled Results from Four Longitudinal Birth Cohort Studies.

BACKGROUND: Organophosphorous (OP) pesticides are associated with reduced fetal growth in animals, but human studies are inconsistent. OBJECTIVES: We pooled data from four cohorts to examine associations of prenatal OP exposure with birth weight (n = 1,169), length (n = 1,152), and head circumference (n = 1,143). METHODS: Data were from the CHAMACOS, HOME, Columbia, and Mount Sinai birth cohorts. Concentrations of three diethyl phosphate (ΣDEP) and three dimethyl phosphate (ΣDMP) metabolites of OP pesticides [summed to six dialkyl phosphates (ΣDAPs)] were measured in maternal urine. Linear regression and mixed-effects models were used to examine associations with birth outcomes. RESULTS: We found no significant associations of ΣDEP, ΣDMP, or ΣDAPs with birth weight, length, or head circumference overall. However, among non-Hispanic black women, increasing urinary ΣDAP and ΣDMP concentrations were associated with decreased birth length (ß = -0.4 cm; 95% CI: -0.9, 0.0 and ß = -0.4 cm; 95% CI: -0.8, 0.0, respectively, for each 10-fold increase in metabolite concentration). Among infants with the PON1192RR genotype, ΣDAP and ΣDMP were negatively associated with length (ß = -0.4 cm; 95% CI: -0.9, 0.0 and ß = -0.5 cm; 95% CI: -0.9, -0.1). CONCLUSIONS: This study confirms previously reported associations of prenatal OP exposure among black women with decreased infant size at birth, but finds no evidence of smaller birth weight, length, or head circumference among whites or Hispanics. Contrary to our hypothesis, we found stronger inverse associations of DAPs and birth outcome in infants with the less susceptible PON1192RR genotype. The large pooled data set facilitated exploration of interactions by race/ethnicity and PON1 genotype, but was limited by differences in study populations. CITATION: Harley KG, Engel SM, Vedar MG, Eskenazi B, Whyatt RM, Lanphear BP, Bradman A, Rauh VA, Yolton K, Hornung RW, Wetmur JG, Chen J, Holland NT, Barr DB, Perera FP, Wolff MS. 2016. Prenatal exposure to organophosphorous pesticides and fetal growth: pooled results from four longitudinal birth cohort studies. Environ Health Perspect 124:1084-1092; http://dx.doi.org/10.1289/ehp.1409362.

Effect of Organic Diet Intervention on Pesticide Exposures in Young Children Living in Low-Income Urban and Agricultural Communities.

BACKGROUND: Recent organic diet intervention studies suggest that diet is a significant source of pesticide exposure in young children. These studies have focused on children living in suburban communities. OBJECTIVES: We aimed to determine whether consuming an organic diet reduced urinary pesticide metabolite concentrations in 40 Mexican-American children, 3-6 years of age, living in California urban and agricultural communities. METHODS: In 2006, we collected urine samples over 16 consecutive days from children who consumed conventionally grown food for 4 days, organic food for 7 days, and then conventionally grown food for 5 days. We measured 23 metabolites, reflecting potential exposure to organophosphorous (OP), pyrethroid, and other pesticides used in homes and agriculture. We used linear mixed-effects models to evaluate the effects of diet on urinary metabolite concentrations. RESULTS: For six metabolites with detection frequencies > 50%, adjusted geometric mean concentrations during the organic phase were generally lower for all children, and were significant for total dialkylphosphates (DAPs) and dimethyl DAPs (DMs; metabolites of OP insecticides) and 2,4-D (2,4-dichlorophenoxyacetic acid, a herbicide), with reductions of 40%, 49%, and 25%, respectively (p < 0.01). Chemical-specific metabolite concentrations for several OP pesticides, pyrethroids, and herbicides were either infrequently detected and/or not significantly affected by diet. Concentrations for most of the frequently detected metabolites were generally higher in Salinas compared with Oakland children, with DMs and metolachlor at or near significance (p = 0.06 and 0.03, respectively). CONCLUSION: An organic diet was significantly associated with reduced urinary concentrations of nonspecific dimethyl OP insecticide metabolites and the herbicide 2,4-D in children. Additional research is needed to clarify the relative importance of dietary and non-dietary sources of pesticide exposures to young children.

Prenatal and postnatal bisphenol A exposure and body mass index in childhood in the CHAMACOS cohort.

BACKGROUND: Bisphenol A (BPA), a widely used endocrine-disrupting chemical, has been associated with increased body weight and fat deposition in rodents. OBJECTIVES: We examined whether prenatal and postnatal urinary BPA concentrations were associated with body mass index (BMI), waist circumference, percent body fat, and obesity in 9-year-old children (n = 311) in the CHAMACOS longitudinal cohort study. METHODS: BPA was measured in spot urine samples collected from mothers twice during pregnancy and from children at 5 and 9 years of age. RESULTS: Prenatal urinary BPA concentrations were associated with decreased BMI at 9 years of age in girls but not boys. Among girls, being in the highest tertile of prenatal BPA concentrations was associated with decreased BMI z-score (ß = -0.47, 95% CI: -0.87, -0.07) and percent body fat (ß = -4.36, 95% CI: -8.37, -0.34) and decreased odds of overweight/obesity [odds ratio (OR) = 0.37, 95% CI: 0.16, 0.91] compared with girls in the lowest tertile. These findings were strongest in prepubertal girls. Urinary BPA concentrations at 5 years of age were not associated with any anthropometric parameters at 5 or 9 years, but BPA concentrations at 9 years were positively associated with BMI, waist circumference, fat mass, and overweight/obesity at 9 years in boys and girls. CONCLUSIONS: Consistent with other cross-sectional studies, higher urinary BPA concentrations at 9 years of age were associated with increased adiposity at 9 years. However, increasing BPA concentrations in mothers during pregnancy were associated with decreased BMI, body fat, and overweight/obesity among their daughters at 9 years of age.

Variability of organophosphorous pesticide metabolite levels in spot and 24-hr urine samples collected from young children during 1 week.

BACKGROUND: Dialkyl phosphate (DAP) metabolites in spot urine samples are frequently used to characterize children's exposures to organophosphorous (OP) pesticides. However, variable exposure and short biological half-lives of OP pesticides could result in highly variable measurements, leading to exposure misclassification. OBJECTIVE: We examined within- and between-child variability in DAP metabolites in urine samples collected during 1 week. METHODS: We collected spot urine samples over 7 consecutive days from 25 children (3-6 years of age). On two of the days, we collected 24-hr voids. We assessed the reproducibility of urinary DAP metabolite concentrations and evaluated the sensitivity and specificity of spot urine samples as predictors of high (top 20%) or elevated (top 40%) weekly average DAP metabolite concentrations. RESULTS: Within-child variance exceeded between-child variance by a factor of two to eight, depending on metabolite grouping. Although total DAP concentrations in single spot urine samples were moderately to strongly associated with concentrations in same-day 24-hr samples (r ≈ 0.6-0.8, p < 0.01), concentrations in spot samples collected > 1 day apart and in 24-hr samples collected 3 days apart were weakly correlated (r ≈ -0.21 to 0.38). Single spot samples predicted high (top 20%) and elevated (top 40%) full-week average total DAP excretion with only moderate sensitivity (≈ 0.52 and ≈ 0.67, respectively) but relatively high specificity (≈ 0.88 and ≈ 0.78, respectively). CONCLUSIONS: The high variability we observed in children's DAP metabolite concentrations suggests that single-day urine samples provide only a brief snapshot of exposure. Sensitivity analyses suggest that classification of cumulative OP exposure based on spot samples is prone to type 2 classification errors.

Maternal urinary bisphenol a during pregnancy and maternal and neonatal thyroid function in the CHAMACOS study.

BACKGROUND: Bisphenol A (BPA) is widely used in the manufacture of polycarbonate plastic bottles, food and beverage can linings, thermal receipts, and dental sealants. Animal and human studies suggest that BPA may disrupt thyroid function. Although thyroid hormones play a determinant role in human growth and brain development, no studies have investigated relations between BPA exposure and thyroid function in pregnant women or neonates. OBJECTIVE: Our goal was to evaluate whether exposure to BPA during pregnancy is related to thyroid hormone levels in pregnant women and neonates. METHODS: We measured BPA concentration in urine samples collected during the first and second half of pregnancy in 476 women participating in the CHAMACOS (Center for the Health Assessment of Mothers and Children of Salinas) study. We also measured free thyroxine (T4), total T4, and thyroid-stimulating hormone (TSH) in women during pregnancy, and TSH in neonates. RESULTS: Associations between the average of the two BPA measurements and maternal thyroid hormone levels were not statistically significant. Of the two BPA measurements, only the one taken closest in time to the TH measurement was significantly associated with a reduction in total T4 (ß = -0.13 µg/dL per log2 unit; 95% CI: -0.25, 0.00). The average of the maternal BPA concentrations was associated with reduced TSH in boys (-9.9% per log2 unit; 95% CI: -15.9%, -3.5%) but not in girls. Among boys, the relation was stronger when BPA was measured in the third trimester of pregnancy and decreased with time between BPA and TH measurements. CONCLUSION: Results suggest that exposure to BPA during pregnancy is related to reduced total T4 in pregnant women and decreased TSH in male neonates. Findings may have implications for fetal and neonatal development.

Utility of urinary Clara cell protein (CC16) to demonstrate increased lung epithelial permeability in non-smokers exposed to outdoor secondhand smoke.

The objective of this study was to assess the utility of urinary Clara cell protein (CC16) as a biomarker of increased lung epithelial permeability in non-smokers exposed to outdoor secondhand smoke. Twenty-eight healthy non-smoking adults visited outdoor patios of a restaurant and a bar where non-participants smoked and an open-air control with no smokers on three weekend days in a crossover study; subjects visited each site once for 3 h. Urine samples were collected at baseline, immediately post exposure and next morning, and analyzed for CC16. Changes in CC16 across location types or with cigarette count were analyzed using mixed-effect models, which included all subjects and stratified by gender. Urinary CC16 was higher in males (n=9) compared with females (n=18) at all measurement occasions (P<0.002), possibly reflecting prostatic contamination. Urinary CC16 from pre-exposure to post-exposure was higher following visits to restaurant and bar sites compared with the control among females but this increase did not reach statistical significance. Post-exposure to pre-exposure urinary CC16 ratios among females increased with cigarette count (P=0.048). Exposure-related increases in urinary CC16 were not seen among males. In conclusion, urinary CC16 may be a useful biomarker of increased lung epithelial permeability among female non-smokers; further work will be required to evaluate its applicability to males.

Cholinesterase and paraoxonase (PON1) enzyme activities in Mexican-American mothers and children from an agricultural community.

Exposure to organophosphate and carbamate pesticides can lead to neurotoxic effects through inhibition of cholinesterase enzymes. The paraoxonase (PON1) enzyme can detoxify oxon derivatives of some organophosphates. Lower PON1, acetylcholinesterase, and butyrylcholinesterase activities have been reported in newborns relative to adults, suggesting increased susceptibility to organophosphate exposure in young children. We determined PON1, acetylcholinesterase, and butyrylcholinesterase activities in Mexican-American mothers and their 9-year-old children (n=202 pairs) living in an agricultural community. We used Wilcoxon signed-rank tests to compare enzymatic activities among mothers and their children, and analysis of variance to identify factors associated with enzyme activities. Substrate-specific PON1 activities were slightly lower in children than their mothers; however, these differences were only statistically significant for the paraoxon substrate. We observed significantly lower acetylcholinesterase but higher butyrylcholinesterase levels in children compared with their mothers. Mean butyrylcholinesterase levels were strongly associated with child obesity status (body mass index Z scores >95%). We observed highly significant correlations among mother-child pairs for each of the enzymatic activities analyzed; however, PON1 activities did not correlate with acetylcholinesterase or butyrylcholinesterase activities. Our findings suggest that by age 9 years, PON1 activities approach adult levels, and host factors including sex and obesity may affect key enzymes involved in pesticide metabolism.

Factors associated with serum polybrominated diphenyl ether (PBDE) levels among school-age children in the CHAMACOS cohort.

Polybrominated diphenyl ethers (PBDEs) are a class of flame retardants historically used in textiles, furniture, and electronic products. Recent studies have documented widespread PBDE exposure to humans, with higher levels measured in children than adults. We analyzed 10 tri- to hepta-BDE congener levels in blood collected from 7-year old Mexican-American children living in an agriculture community in California (n = 272). The most frequently detected PBDE congeners in child serum were BDE-47, -99, -100, and -153, all of which were measured in >99% of the children. We used multiple linear regression models to examine associations between child total PBDE levels (ng/g lipid) and determinants of exposure. Factors positively associated with higher PBDE levels in the children were total PBDE levels in maternal serum during pregnancy, duration of exclusive breastfeeding, and having no safe places to play in their neighborhood. Child BMI was inversely associated with serum PBDE levels (regression p-values <0.05). Our findings confirm that exposure to the penta-BDE mixture is ongoing, and that Mexican-American children living in California may be experiencing higher PBDE exposure from their environment compared to children sampled from the general U.S. population. Additional research is needed to assess the health impacts of these exposures.

Exposure to secondhand smoke outside of a bar and a restaurant and tobacco exposure biomarkers in nonsmokers.

BACKGROUND: With an increase in indoor smoking bans, many smokers smoke outside establishments and near their entrances, which has become a public health concern. OBJECTIVES: We characterized the exposure of nonsmokers to secondhand smoke (SHS) outside a restaurant and bar in Athens, Georgia, where indoor smoking is banned, using salivary cotinine and urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL). METHODS: In a crossover study, we assigned 28 participants to outdoor patios of a restaurant and a bar and an open-air site with no smokers on three weekend days; participants visited each site once and stayed for 3 hr. We collected saliva and urine samples immediately before and after the visits (postexposure) and on the following morning and analyzed samples for cotinine and total NNAL, respectively. Regression models were fitted and changes in biomarkers were contrasted between locations. RESULTS: Postexposure and preexposure geometric mean salivary cotinine concentrations differed by 0.115 ng/mL [95% confidence interval (CI): 0.105, 0.126)] and by 0.030 ng/mL (95% CI: 0.028, 0.031) for bar and restaurant visits, respectively. There were no significant post- and preexposure differences in cotinine levels after control site visits, and changes after bar and restaurant site visits were significantly different from changes after control site visits (p < 0.001). Results comparing next-day and preexposure salivary cotinine levels were similar. Next-day creatinine-corrected urinary NNAL concentrations also were higher than preexposure levels following bar and restaurant visits [1.858 pg/mg creatinine higher (95% CI: 0.897, 3.758) and 0.615 pg/mg creatinine higher (95% CI: 0.210, 1.761), respectively], and were significantly different from changes after the control visits (p = 0.005). CONCLUSION: Salivary cotinine and urinary NNAL increased significantly in nonsmokers after outdoor SHS exposure. Our findings indicate that such exposures may increase risks of health effects associated with tobacco carcinogens.

Association of organophosphate pesticide exposure and paraoxonase with birth outcome in Mexican-American women.

BACKGROUND: Epidemiologic studies suggest that maternal organophosphorus (OP) pesticide exposure is associated with poorer fetal growth, but findings are inconsistent. We explored whether paraoxonase (PON1), a key enzyme involved in detoxification of OPs, could be an effect modifier in this association. METHODS: The study population included 470 pregnant women enrolled in the CHAMACOS Study, a longitudinal cohort study of mothers and children living in an agricultural region of California. We analyzed urine samples collected from mothers twice during pregnancy for dialkyl phosphate (DAP) metabolites of OP pesticides. We analyzed maternal and fetal (cord) blood samples for PON1 genotype (PON1(192) and PON1(-108)) and enzyme activity (paraoxonase and arylesterase). Infant birth weight, head circumference, and gestational age were obtained from medical records. RESULTS: Infants' PON1 genotype and activity were associated with birth outcome, but mothers' were not. Infants with the susceptible PON1(-108TT) genotype had shorter gestational age (ß = -0.5 weeks, 95% Confidence Interval (CI): -0.9, 0.0) and smaller head circumference (ß = -0.4 cm, 95% CI: -0.7, 0.0) than those with the PON1(-108CC) genotype. Infants' arylesterase and paraoxonase activity were positively associated with gestational age. There was some evidence of effect modification with DAPs: maternal DAP concentrations were associated with shorter gestational age only among infants of the susceptible PON1(-108TT) genotype (p-value(interaction) = 0.09). However, maternal DAP concentrations were associated with larger birth weight (p-value(interaction) = 0.06) and head circumference (p-value(interaction)<0.01) in infants with non-susceptible genotypes. CONCLUSIONS: Infants whose PON1 genotype and enzyme activity levels suggested that they might be more susceptible to the effects of OP pesticide exposure had decreased fetal growth and length of gestation. PON1 may be another factor contributing to preterm or low birth weight birth.

Biomarkers of immunotoxicity for environmental and public health research.

The immune response plays an important role in the pathophysiology of numerous diseases including asthma, autoimmunity and cancer. Application of biomarkers of immunotoxicity in epidemiology studies and human clinical trials can improve our understanding of the mechanisms that underlie the associations between environmental exposures and development of these immune-mediated diseases. Immunological biomarkers currently used in environmental health studies include detection of key components of innate and adaptive immunity (e.g., complement, immunoglobulin and cell subsets) as well as functional responses and activation of key immune cells. The use of high-throughput assays, including flow cytometry, Luminex, and Multi-spot cytokine detection methods can further provide quantitative analysis of immune effects. Due to the complexity and redundancy of the immune response, an integrated assessment of several components of the immune responses is needed. The rapidly expanding field of immunoinformatics will also aid in the synthesis of the vast amount of data being generated. This review discusses and provides examples of how the identification and development of immunological biomarkers for use in studies of environmental exposures and immune-mediated disorders can be achieved.

Cellular function of neuropathy target esterase in lysophosphatidylcholine action.

Neuropathy target esterase (NTE) plays critical roles in embryonic development and maintenance of peripheral axons. It is a secondary target of some organophosphorus toxicants including analogs of insecticides and chemical warfare agents. Although the mechanistic role of NTE in vivo is poorly defined, it is known to hydrolyze lysophosphatidylcholine (LPC) in vitro and may protect cell membranes from cytotoxic accumulation of LPC. To determine the cellular function of NTE, Neuro-2a and COS-7 cells were transfected with a full-length human NTE-containing plasmid yielding recombinant NTE (rNTE). We find the same inhibitor sensitivity and specificity profiles for rNTE assayed with LPC or phenyl valerate (a standard NTE substrate) and that this correlation extends to the LPC hydrolases of human brain, lymphocytes and erythrocytes. All of these LPC hydrolases are therefore very similar to each other in respect to a conserved inhibitor binding site conformation. NTE is expressed in brain and lymphocytes and contributes to LPC hydrolase activities in these tissues. The enzyme or enzymes responsible for erythrocyte LPC hydrolase activity remain to be identified. We also show that rNTE protects Neuro-2a and COS-7 cells from exogenous LPC cytotoxicity. Expression of rNTE in Neuro-2a cells alters their phospholipid balance (analyzed by liquid chromatography-mass spectrometry with single ion monitoring) by lowering LPC-16:0 and LPC-18:0 and elevating glycerophosphocholine without a change in phosphatidylcholine-16:0/18:1 or 16:0/18:2. NTE therefore serves an important function in LPC homeostasis and action.

Lysophosphatidylcholine hydrolases of human erythrocytes, lymphocytes, and brain: sensitive targets of conserved specificity for organophosphorus delayed neurotoxicants.

Brain neuropathy target esterase (NTE), associated with organophosphorus (OP)-induced delayed neuropathy, has the same OP inhibitor sensitivity and specificity profiles assayed in the classical way (paraoxon-resistant, mipafox-sensitive hydrolysis of phenyl valerate) or with lysophosphatidylcholine (LysoPC) as the substrate. Extending our earlier observation with mice, we now examine human erythrocyte, lymphocyte, and brain LysoPC hydrolases as possible sensitive targets for OP delayed neurotoxicants and insecticides. Inhibitor profiling of human erythrocytes and lymphocytes gave the surprising result of essentially the same pattern as with brain. Human erythrocyte LysoPC hydrolases are highly sensitive to OP delayed neurotoxicants, with in vitro IC50 values of 0.13-85 nM for longer alkyl analogs, and poorly sensitive to the current OP insecticides. In agricultural workers, erythrocyte LysoPC hydrolyzing activities are similar for newborn children and their mothers and do not vary with paraoxonase status but have high intersample variation that limits their use as a biomarker. Mouse erythrocyte LysoPC hydrolase activity is also of low sensitivity in vitro and in vivo to the OP insecticides whereas the delayed neurotoxicant ethyl n-octylphosphonyl fluoride inhibits activity in vivo at 1-3 mg/kg. Overall, inhibition of blood LysoPC hydrolases is as good as inhibition of brain NTE as a predictor of OP inducers of delayed neuropathy. NTE and lysophospholipases (LysoPLAs) both hydrolyze LysoPC, yet they are in distinct enzyme families with no sequence homology and very different catalytic sites. The relative contributions of NTE and LysoPLAs to LysoPC hydrolysis and clearance from erythrocytes, lymphocytes, and brain remain to be defined.

Cytokines and other immunological biomarkers in children's environmental health studies.

Environmental exposures (e.g. pesticides, air pollution, and environmental tobacco smoke) during prenatal and early postnatal development have been linked to a growing number of childhood diseases including allergic disorders and leukemia. Because the immune response plays a critical role in each of these diseases, it is important to study the effects of toxicants on the developing immune system. Children's unique susceptibility to environmental toxicants has become an important focus of the field of immunotoxicology and the use of immune biomarkers in molecular epidemiology of children's environmental health is a rapidly expanding field of research. In this review, we discuss how markers of immune status and immunotoxicity are being applied to pediatric studies, with a specific focus on the various methods used to analyze T-helper-1/2 (Th1/Th2) cytokine profiles. Furthermore, we review recent data on the effects of children's environmental exposures to volatile organic compounds, metals, and pesticides on Th1/Th2 cytokine profiles and the associations of Th1/Th2 profiles with adverse health outcomes such as pediatric respiratory diseases, allergies, cancer and diabetes. Although cytokine profiles are increasingly used in children's studies, there is still a need to acquire distribution data for different ages and ethnic groups of healthy children. These data will contribute to the validation and standardization of cytokine biomarkers for future studies. Application of immunological markers in epidemiological studies will improve the understanding of mechanisms that underlie associations between environmental exposures and immune-mediated disorders.

Factors predicting organochlorine pesticide levels in pregnant Latina women living in a United States agricultural area.

Organochlorine (OC) pesticide use was restricted starting in the 1970s in developed countries and the 1980s and 1990s in developing countries. Current exposure to OC pesticides - dichlorodiphenyltrichloroethane (DDT), lindane (99% pure gamma-hexachlorocyclohexane (gamma-HCH)), hexachlorobenzene (HCB) - occurs on a limited basis. We measured para, para' (p,p')-DDE, p,p'-DDT, ortho, para' (o,p')-DDT, HCB, beta (beta)-HCH (the most persistent isomer of technical-grade HCH) and gamma-HCH in serum from 426 low-income pregnant Latina women living in an agricultural community in California. Detection frequencies were 94% to 100%. Median levels (ng/g lipid) of p,p'-DDE (1,052), p,p'-DDT (13), beta-HCH (37) and HCB (65) were significantly higher than United States population levels. Multivariate analyses of p,p'-DDE, p,p'-DDT, o,p'-DDT, beta-HCH and HCB indicate that time spent living outside the United States and birthplace in an area of Mexico with recent use of OC pesticides were significant predictors of exposure. Time spent living in the United States was associated with increased serum levels of p,p'-DDE and beta-HCH, but the increase for each year lived in the United States was lower than for each year lived outside the United States. There was no difference between the increase of HCB levels over time spent in or outside the United States, suggesting current and thus preventable exposure routes. However, we observed no associations between serum levels of any OC compound and current intake of saturated fat or agricultural take-home exposure risk factors. Lactation history and recent weight gain were negatively associated with serum levels of some, but not all OC compounds studied. Smoking history was borderline associated with elevated HCB levels. We observed no significant associations with body mass index. Although the weight of evidence from this study indicates that most exposure occurred before moving to the United States, the results for HCB indicate the possibility of ongoing exposure in this country.

Early environmental exposures and intracellular Th1/Th2 cytokine profiles in 24-month-old children living in an agricultural area.

BACKGROUND: Children who reside in agricultural settings are potentially exposed to higher levels of organophosphate (OP) pesticides, endotoxin, and allergens than their urban counterparts. Endotoxin and allergens stimulate maturation of the immune response in early childhood, but little is known about the effect of exposures to OPs or to the three combined. OBJECTIVES: In this study, we investigated the relationships between these exposures and T-helper 1 (Th1) and T-helper 2 (Th2) cytokines, biomarkers of allergic asthma, in the subjects of CHAMACOS (Center for the Health Assessment of Mothers and Children of Salinas), a longitudinal birth cohort in Salinas Valley, California. Exposures were ascertained by interviewer-administered questionnaires and by home visits, and clinical diagnoses were abstracted from medical records. Blood samples were collected at 12 and 24 months of age and analyzed for Th1/Th2 status by flow cytometric detection of intracellular interferon-gamma/interleukin-4 cytokine expression. FINDINGS: Mean Th2 levels were significantly higher in children with doctor-diagnosed asthma and children with wheezing at 2 years of age. In a multiple linear regression model, exclusive breast-feeding at 1 month and pet ownership were associated with 35.3% (p < 0.01) and 34.5% (p = 0.01) increases in Th1, respectively. Maternal agricultural work and presence of gas stove in the home were associated with a 25.9% increase (p = 0.04) and 46.5% increase (p < 0.01) in Th2, respectively. CONCLUSIONS: Asthma and wheeze outcomes in children at 24 months of age are associated with elevated Th2 status in children at an early age. Our data further suggest that early exposures to an agricultural environment, breast-feeding, pets, and gas stoves affect the development of children's Th1/Th2 immune response.