Proximity to endocrine-disrupting pesticides and risk of testicular germ cell tumors (TGCT) among adolescents: A population-based case-control study in California

BACKGROUND

The incidence of testicular germ cell tumors (TGCT) is increasing steadily in the United States, particularly among Latinos. TGCT is thought to be initiated in utero and exposure to endocrine-disrupting chemicals, suspected contributors to TGCT pathogenesis, during this critical developmental period may contribute to the rise.

OBJECTIVES

To assess the relationship between fetal exposure to agricultural endocrine-disrupting pesticides (EDPs) and TGCT risk among adolescents in a diverse population in California.

METHODS

We conducted a registry-based case-control study of TGCT. Cases, diagnosed between 1997 and 2011, were 15-19 years of age (n = 381). Controls were matched on birth year and race/ethnicity (n = 762). Quantities (kilograms) of 33 pesticides applied within 3 km and 1 km radii of each individual's address before birth were estimated using the Pesticide Use Reporting database. Odds ratios (OR), 95% confidence intervals (CI), and population attributable risk (PAR) were calculated for each EDP (using log-2 transformed values). Risk models considered race/ethnicity, birth year, and neighborhood socioeconomic status.

RESULTS

A doubling of nearby acephate applications (3 km and 1 km radii) and malathion applications (1 km radius) was associated with increased risks of TGCT among Latinos only (OR = 1.09; 95% CI:1.01-1.17; 1.30; 95% CI:1.08-1.57, and 1.19; 95% CI:1.01-1.39, respectively), whereas application of carbaryl within a 3 km radius increased TGCT risk in non-Latinos only (OR = 1.14, 95% CI:1.01-1.28). We estimate that acephate was associated with approximately 10% of the TGCT PAR, malathion with 3% and carbaryl with 1%.

CONCLUSIONS

TGCT among adolescents in California was associated with prenatal residential proximity to acephate and malathion among Latinos, and with carbaryl among non-Latinos. These results suggest that the rise in TGCT risk among Latinos may be associated with exposure to these pesticides.

Latent profiles of children's autonomic nervous system reactivity early in life predict later externalizing problems

Prior researchers have observed relations between children's autonomic nervous system reactivity and externalizing behavior problems, but rarely considers the role of developmentally regulated changes in children's stress response systems. Using growth mixture modeling, the present study derived profiles of parasympathetic nervous system reactivity (as indicated by respiratory sinus arrhythmia (RSA)) and sympathetic nervous system reactivity (as indicated by pre-ejection period (PEP)) from low income, primarily Mexican American children measured repeatedly from infancy through age 5 (N = 383) and investigated whether profiles were associated with externalizing problems at age 7. Analyses identified two profiles of RSA reactivity (reactive decreasing and U-shaped reactivity) and three profiles of PEP reactivity (blunted/anticipatory reactivity, reactive decreasing, non-reactive increasing). Compared to children with an RSA profile of reactive decreasing, those with an RSA profile of U-shaped reactivity had marginally higher externalizing problems, however, this difference was not statistically significant. Children who demonstrated a profile of blunted/anticipatory PEP reactivity had significantly higher externalizing problems compared to those with a profile of non-reactive increasing, likely related to the predominantly male composition of the former profile and predominantly female composition of the latter profile. Findings contribute to our understanding of developmental trajectories of ANS reactivity and highlight the utility of a longitudinal framework for understanding the effects of physiological risk factors on later behavior problems.

Abstract PO-125: Prenatal proximity to agricultural use of endocrine-disrupting pesticides and risk of testicular germ cell tumor (TGCT) among Latino and non-Latino adolescents in California

BACKGROUND. Incidence of testicular germ cell tumors (TGCTs) has increased steadily in the United States in recent years, especially among Latinos. TGCT initiation is believed to occur during fetal development and to be related to endocrine disruption; the increasing prevalence of in utero exposures to endocrine- disrupting chemicals may have contributed to the rise in the disease’s incidence.

METHODS. This registry-based case-control study included 381 California-born patients diagnosed with TGCT at age 15-19 years from 1997-2011 (336 non- seminomas, 41 seminomas) and 762 controls matched on birth year and race/ethnicity. We assessed the agricultural application of 22 endocrine-disrupting pesticides (EDPs) using California’s Pesticide Use Reporting (PUR) database for an area within a 3km radius of participants’ birth address in the year prior to birth; 15 high-volume EDPs (those to which 50 or more participants were potentially exposed) were included in statistical analyses. We used logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for log2-transformed continuous pesticide levels, and to calculate attributable risk (AR) for dichotomous exposure (zero and low application vs. high application). Analyses accounted for the timing of pesticide application, histologic subtype, race/ethnicity, birth year, and neighborhood socioeconomic status (SES). RESULTS. Overall, 48% of cases and 45% of controls lived within 3km of an EDP application in the year before birth. Nearby pesticide applications were greater among Latinos than non-Latinos for 13 of 15 EDPs; the median [interquartile range (IQR)] for total EDP application was 29 kg [5- 135] vs. 11 kg [1-80]. Application was also greater for those born after 1990 (the period of time with complete PUR reporting) than before 1990 for 14 of 15 EDPs (median [IQR] for total EDP application: 54 kg [10-229] vs. 13 kg [0.7-70]). Analyses of individual EDPs showed an increased risk of TGCT associated with acephate (OR [95%CI]: 1.1 [1.0-1.2] and 1.3 [1.0-1.7] for continuous and binary exposures, respectively). In analyses stratified by ethnicity, risk remained elevated for acephate application among Latinos (n=614, OR [95% CI] for continuous exposure model: 1.1 [1.0-1.2]) and for carbaryl and copper sulfate in non-Latinos (n=504, OR [95% CI]: 1.2 [1.0-1.3] and 1.1 [1.0-1.3], respectively). Overall there were no differences by PUR reporting period (before and after 1990) and application timing (preconception and trimesters), yet risk appeared to be higher for non-seminomas and among high SES participants. The population AR for high levels of acephate was 5.4% among Latinos, and <1% prior to 1990 vs. 10% after 1990 for all subjects combined. In non-Latinos, the AR for carbaryl was 4.8% and 2.5% for copper sulfate. CONCLUSIONS. Acephate, an organophosphate insecticide, was associated with an increased TGCT risk, possibly contributing 5-10% to the prevalence of TGCT among Latinos in California.

Citation Format: Scott J. Swartz, Libby Morimoto, Todd Whitehead, Robert Gunier, Joseph Wiemels, Xiaomei Ma, Catherine Metayer. Prenatal proximity to agricultural use of endocrine-disrupting pesticides and risk of testicular germ cell tumor (TGCT) among Latino and non-Latino adolescents in California [abstract]. In: Proceedings of the AACR Virtual Conference: Thirteenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2020 Oct 2-4. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(12 Suppl):Abstract nr PO-125.

Prenatal exposure to organophosphate pesticides and functional neuroimaging in adolescents living in proximity to pesticide application

We have reported consistent associations of prenatal organophosphate pesticide (OP) exposure with poorer cognitive function and behavior problems in our Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS), a birth cohort of Mexican American youth in California's agricultural Salinas Valley. However, there is little evidence on how OPs affect neural dynamics underlying associations. We used functional near-infrared spectroscopy (fNIRS) to measure cortical activation during tasks of executive function, attention, social cognition, and language comprehension in 95 adolescent CHAMACOS participants. We estimated associations of residential proximity to OP use during pregnancy with cortical activation in frontal, temporal, and parietal regions using multiple regression models, adjusting for sociodemographic characteristics. OP exposure was associated with altered brain activation during tasks of executive function. For example, with a 10-fold increase in total OP pesticide use within 1 km of maternal residence during pregnancy, there was a bilateral decrease in brain activation in the prefrontal cortex during a cognitive flexibility task (β = -4.74; 95% CI: -8.18, -1.31 and β = -4.40; 95% CI: -7.96, -0.84 for the left and right hemispheres, respectively). We also found that prenatal OP exposure was associated with sex differences in brain activation during a language comprehension task. This first functional neuroimaging study of prenatal OP exposure suggests that pesticides may impact cortical brain activation, which could underlie previously reported OP-related associations with cognitive and behavioral function. Use of fNIRS in environmental epidemiology offers a practical alternative to neuroimaging technologies and enhances our efforts to assess the impact of chemical exposures on neurodevelopment.

Association of Perceived Immigration Policy Vulnerability With Mental and Physical Health Among US-Born Latino Adolescents in California

IMPORTANCE

Current US immigration policy targets immigrants from Mexico and other Latin American countries; anti-immigration rhetoric has possible implications for the US-born children of immigrant parents.

OBJECTIVE

To assess whether concerns about immigration policy are associated with worse mental and physical health among US citizen children of Latino immigrants.

DESIGN, SETTING, AND PARTICIPANTS

This study of cohort data from the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS), a long-term study of Mexican farmworker families in the Salinas Valley region of California, included a sample of US-born adolescents (n = 397) with at least 1 immigrant parent. These adolescents underwent a health assessment before the 2016 presidential election (at age 14 years) and in the first year after the election (at age 16 years). Data were analyzed from March 23, 2018, to February 14, 2019.

EXPOSURES

Adolescents aged 16 years self-reported their concern about immigration policy using 2 subscales (Threat to Family and Children's Vulnerability) of the Perceived Immigration Policy Effects Scale (PIPES) instrument.

MAIN OUTCOMES AND MEASURES

Resting systolic blood pressure, diastolic blood pressure, and mean arterial pressure; body mass index; maternal- and self-reported depression and anxiety problems (using Behavioral Assessment System for Children, 2nd edition); self-reported sleep quality (using Pittsburgh Sleep Quality Index [PSQI]); and maternal rating of child's overall health. All measures except sleep quality were assessed at both the aged-14-years and aged-16-years visits. Health outcomes at age 16 years and the change in outcomes between ages 14 and 16 years were examined among youth participants who reported low or moderate PIPES scores vs high PIPES scores.

RESULTS

In the sample of 397 US-born Latino adolescents (207 [52.1%] female) and primarily Mexican American individuals, nearly half of the youth participants worried at least sometimes about the personal consequences of the US immigration policy (n = 178 [44.8%]), family separation because of deportation (177 [44.6%]), and being reported to the immigration office (164 [41.3%]). Those with high compared with low or moderate PIPES scores had higher self-reported mean anxiety T scores (5.43; 95% CI, 2.64-8.23), higher maternally reported anxiety T scores (2.98; 95% CI, 0.53-5.44), and worse PSQI scores (0.98; 95% CI, 0.36-1.59). Youth participants with high PIPES scores reported statistically significantly increased levels of anxiety over the 2 visits (adjusted mean difference-in-differences, 2.91; 95% CI, 0.20-5.61) and not significantly increased levels of depression (adjusted mean difference-in-differences, 2.63; 95% CI, -0.28 to 5.54).

CONCLUSIONS AND RELEVANCE

Fear and worry about the personal consequences of current US immigration policy and rhetoric appear to be associated with higher anxiety levels, sleep problems, and blood pressure changes among US-born Latino adolescents; anxiety significantly increased after the 2016 presidential election.

Metabolomic Markers of Phthalate Exposure in Plasma and Urine of Pregnant Women

Phthalates are known endocrine disruptors and found in almost all people with several associated adverse health outcomes reported in humans and animal models. Limited data are available on the relationship between exposure to endocrine disrupting chemicals and the human metabolome. We examined the relationship of metabolomic profiles in plasma and urine of 115 pregnant women with eleven urine phthalate metabolites measured at 26 weeks of gestation to identify potential biomarkers and relevant pathways. Targeted metabolomics was performed by selected reaction monitoring liquid chromatography and triple quadrupole mass spectrometry to measure 415 metabolites in plasma and 151 metabolites in urine samples. We have chosen metabolites with the best defined peaks for more detailed analysis (138 in plasma and 40 in urine). Relationship between urine phthalate metabolites and concurrent metabolomic markers in plasma and urine suggested potential involvement of diverse pathways including lipid, steroid, and nucleic acid metabolism and enhanced inflammatory response. Most of the correlations were positive for both urine and plasma, and further confirmed by regression and PCA analysis. However, after the FDR adjustment for multiple comparisons, only 9 urine associations remained statistically significant (q-values 0.0001–0.0451), including Nicotinamide mononucleotide, Cysteine T2, Cystine, and L-Aspartic acid. Additionally, we found negative associations of maternal pre-pregnancy body mass index (BMI) with more than 20 metabolomic markers related to lipid and amino-acid metabolism and inflammation pathways in plasma (p = 0.01–0.0004), while Mevalonic acid was positively associated (p = 0.009). Nicotinic acid, the only significant metabolite in urine, had a positive association with maternal BMI (p = 0.002). In summary, when evaluated in the context of metabolic pathways, the findings suggest enhanced lipid biogenesis, inflammation and altered nucleic acid metabolism in association with higher phthalate levels. These results provide new insights into the relationship between phthalates, common in most human populations, and metabolomics, a novel approach to exposure and health biomonitoring.

DNA methylation and socioeconomic status in a Mexican-American birth cohort

Background

Maternal social environmental stressors during pregnancy are associated with adverse birth and child developmental outcomes, and epigenetics has been proposed as a possible mechanism for such relationships.

Methods

In a Mexican-American birth cohort of 241 maternal-infant pairs, cord blood samples were measured for repeat element DNA methylation (LINE-1 and Alu). Linear mixed effects regression was used to model associations between indicators of the social environment (low household income and education, neighborhood-level characteristics) and repeat element methylation. Results from a dietary questionnaire were also used to assess the interaction between maternal diet quality and the social environment on markers of repeat element DNA methylation.

Results

After adjusting for confounders, living in the most impoverished neighborhoods was associated with higher cord blood LINE-1 methylation (β = 0.78, 95%CI 0.06, 1.50, p = 0.03). No other neighborhood-, household-, or individual-level socioeconomic indicators were significantly associated with repeat element methylation. We observed a statistical trend showing that positive association between neighborhood poverty and LINE-1 methylation was strongest in cord blood of infants whose mothers reported better diet quality during pregnancy (pinteraction = 0.12).

Conclusion

Our findings indicate a small yet unexpected positive association between neighborhood-level poverty during pregnancy and methylation of repetitive element DNA in infant cord blood and that this association is possibly modified by diet quality during pregnancy. However, our null findings for other adverse SES indicators do not provide strong evidence for an adverse association between early-life socioeconomic environment and repeat element DNA methylation in infants.

Association between Pesticide Profiles Used on Agricultural Fields near Maternal Residences during Pregnancy and IQ at Age 7 Years

We previously showed that potential prenatal exposure to agricultural pesticides was associated with adverse neurodevelopmental outcomes in children, yet the effects of joint exposure to multiple pesticides is poorly understood. In this paper, we investigate associations between the joint distribution of agricultural use patterns of multiple pesticides (denoted as "pesticide profiles") applied near maternal residences during pregnancy and Full-Scale Intelligence Quotient (FSIQ) at 7 years of age. Among a cohort of children residing in California's Salinas Valley, we used Pesticide Use Report (PUR) data to characterize potential exposure from use within 1 km of maternal residences during pregnancy for 15 potentially neurotoxic pesticides from five different chemical classes. We used Bayesian profile regression (BPR) to examine associations between clustered pesticide profiles and deficits in childhood FSIQ. BPR identified eight distinct clusters of prenatal pesticide profiles. Two of the pesticide profile clusters exhibited some of the highest cumulative pesticide use levels and were associated with deficits in adjusted FSIQ of -6.9 (95% credible interval: -11.3, -2.2) and -6.4 (95% credible interval: -13.1, 0.49), respectively, when compared with the pesticide profile cluster that showed the lowest level of pesticides use. Although maternal residence during pregnancy near high agricultural use of multiple neurotoxic pesticides was associated with FSIQ deficit, the magnitude of the associations showed potential for sub-additive effects. Epidemiologic analysis of pesticides and their potential health effects can benefit from a multi-pollutant approach to analysis.

Residential proximity to organophosphate and carbamate pesticide use during pregnancy, poverty during childhood, and cognitive functioning in 10-year-old children

BACKGROUND

Low-income communities and communities of color have been shown to experience disproportionate exposure to agricultural pesticides, which have been linked to poorer neurobehavioral outcomes in infants and children. Few studies have assessed health impacts of pesticide mixtures in the context of socioeconomic adversity.

OBJECTIVES

To examine associations between residential proximity to toxicity-weighted organophosphate (OP) and carbamate pesticide use during pregnancy, household- and neighborhood-level poverty during childhood, and IQ scores in 10-year-old children.

METHODS

We evaluated associations between both nearby agricultural pesticide use and poverty measures and cognitive abilities in 10-year-old children (n = 501) using data from a longitudinal birth cohort study linked with data from the California Pesticide Use Reporting system and the American Community Survey. Associations were assessed using multivariable linear regression.

RESULTS

Children of mothers in the highest quartile compared to the lowest quartile of proximal pesticide use had lower performance on Full Scale IQ [β = -3.0; 95% Confidence Interval (CI) = (-5.6, -0.3)], Perceptual Reasoning [β = -4.0; (-7.6, -0.4)], and Working Memory [β = -2.8; (-5.6, -0.1)]. Belonging to a household earning an income at or below the poverty threshold was associated with approximately two point lower scores on Full Scale IQ, Verbal Comprehension, and Working Memory. Living in the highest quartile of neighborhood poverty at age 10 was associated with approximately four point lower performance on Full Scale IQ, Verbal Comprehension, Perceptual Reasoning, and Working memory.

CONCLUSIONS

Residential proximity to OP and carbamate pesticide use during pregnancy and both household- and neighborhood-level poverty during childhood were independently associated with poorer cognitive functioning in children at 10 years of age.

Reducing chemical exposures in nail salons through owner and worker trainings: an exploratory intervention study

BACKGROUND

Nail salons represent a rapidly growing industry with mainly Vietnamese immigrant workers. Workers routinely handle nail products containing hazardous compounds, yet have limited accessible information to minimize workplace exposures.

METHODS

We conducted a culturally appropriate pilot intervention on workplace chemical exposure reduction strategies. We trained eight Vietnamese owners, who then trained Vietnamese workers in their salons. We conducted pre-, mid-, and post-intervention assessments with workers, including an in-person survey and personal air monitoring of volatile compounds.

RESULTS

Survey results suggested statistically significant increases for chemical knowledge and behavioral changes in glove and mask use, and a reduced prevalence of nose, throat, and skin irritations. Air monitoring results showed a net reduction for methyl methacrylate and total volatile organic compounds, but not for toluene.

CONCLUSIONS

Worker education disseminated through salon owners to their workers can improve work-related knowledge, behavior, health symptoms, and exposures for select air contaminants, although more research is warranted.

Characterization of residential pesticide use and chemical formulations through self-report and household inventory: the Northern California Childhood Leukemia study

BACKGROUND

Home and garden pesticide use has been linked to cancer and other health outcomes in numerous epidemiological studies. Exposure has generally been self-reported, so the assessment is potentially limited by recall bias and lack of information on specific chemicals.

OBJECTIVES

As part of an integrated assessment of residential pesticide exposure, we identified active ingredients and described patterns of storage and use.

METHODS

During a home interview of 500 residentially stable households enrolled in the Northern California Childhood Leukemia Study during 2001-2006, trained interviewers inventoried residential pesticide products and queried participants about their storage and use. U.S. Environmental Protection Agency registration numbers, recorded from pesticide product labels, and pesticide chemical codes were matched to public databases to obtain information on active ingredients and chemical class. Poisson regression was used to identify independent predictors of pesticide storage. Analyses were restricted to 259 participating control households.

RESULTS

Ninety-five percent (246 of 259) of the control households stored at least one pesticide product (median, 4). Indicators of higher sociodemographic status predicted more products in storage. We identified the most common characteristics: storage areas (garage, 40%; kitchen, 20%), pests treated (ants, 33%; weeds, 20%), pesticide types (insecticides, 46%; herbicides, 24%), chemical classes (pyrethroids, 77%; botanicals, 50%), active ingredients (pyrethrins, 43%) and synergists (piperonyl butoxide, 42%). Products could contain multiple active ingredients.

CONCLUSIONS

Our data on specific active ingredients and patterns of storage and use will inform future etiologic analyses of residential pesticide exposures from self-reported data, particularly among households with young children.

Characterizing workplace exposures in Vietnamese women working in California nail salons

OBJECTIVES

We engaged Vietnamese nail salon workers in a community-based participatory research (CBPR) study to measure personal and area concentrations of solvents in their workplace.

METHODS

We measured average work-shift concentrations of toluene, ethyl acetate, and isopropyl acetate among 80 workers from 20 salons using personal air monitors. We also collected area samples from 3 salons using summa canisters.

RESULTS

For personal measurements, the arithmetic mean was 0.53 parts per million (range = 0.02-5.50) for ethyl acetate, 0.04 parts per million (range = 0.02-0.15) for isopropyl acetate, and 0.15 parts per million (range = 0.02-1.0) for toluene. Area measurements were lower in comparison, but we detected notable levels of methyl methacrylate, a compound long banned from nail products. Predictors of solvent levels included different forms of ventilation and whether the salon was located in an enclosed building.

CONCLUSIONS

Using a CBPR approach that engaged community members in the research process contributed to the successful recruitment of salon workers. Measured levels of toluene, methyl methacrylate, and total volatile organic compounds were higher than recommended guidelines to prevent health symptoms such as headaches, irritations, and breathing problems, which were frequently reported in this workforce.

Residential proximity to agricultural pesticide applications and childhood acute lymphoblastic leukemia

Ambient exposure from residential proximity to applications of agricultural pesticides may contribute to the risk of childhood acute lymphoblastic leukemia (ALL). Using residential histories collected from the families of 213 ALL cases and 268 matched controls enrolled in the Northern California Childhood Leukemia Study, the authors assessed residential proximity within a half-mile (804.5m) of pesticide applications by linking address histories with reports of agricultural pesticide use. Proximity was ascertained during different time windows of exposure, including the first year of life and the child's lifetime through the date of diagnosis for cases or reference for controls. Agricultural pesticides were categorized a priori into groups based on similarities in toxicological effects, physicochemical properties, and target pests or uses. The effects of moderate and high exposure for each group of pesticides were estimated using conditional logistic regression. Elevated ALL risk was associated with lifetime moderate exposure, but not high exposure, to certain physicochemical categories of pesticides, including organophosphates, chlorinated phenols, and triazines, and with pesticides classified as insecticides or fumigants. A similar pattern was also observed for several toxicological groups of pesticides. These findings suggest future directions for the identification of specific pesticides that may play a role in the etiology of childhood leukemia.

Is house-dust nicotine a good surrogate for household smoking?

The literature is inconsistent regarding associations between parental smoking and childhood leukemia, possibly because previous studies used self-reported smoking habits as surrogates for children's true exposures to cigarette smoke. Here, the authors investigated the use of nicotine concentrations in house dust as measures of children's exposure to cigarette smoke in 469 households from the Northern California Childhood Leukemia Study (1999-2007). House dust was collected by using high-volume surface samplers and household vacuum cleaners and was analyzed for nicotine via gas chromatography-mass spectrometry. Using multivariable linear regression, the authors evaluated the effects of self-reported parental smoking, parental demographics, house characteristics, and other covariates on house-dust nicotine concentrations. They observed that nicotine concentrations in house dust were associated with self-reported smoking for periods of months and years before dust collection. Furthermore, the authors found that the relation between nicotine dust levels and self-reported smoking varied by parental age and socioeconomic status. These findings suggest that house-dust nicotine concentrations reflect long-term exposures to cigarette smoke in the home and that they may be less biased surrogates for children's exposures to cigarette smoke than self-reported smoking habits.

Autism spectrum disorders in relation to distribution of hazardous air pollutants in the san francisco bay area

OBJECTIVE

To explore possible associations between autism spectrum disorders (ASD) and environmental exposures, we linked the California autism surveillance system to estimated hazardous air pollutant (HAP) concentrations compiled by the U.S. Environmental Protection Agency.

METHODS

Subjects included 284 children with ASD and 657 controls, born in 1994 in the San Francisco Bay area. We assigned exposure level by census tract of birth residence for 19 chemicals we identified as potential neurotoxicants, developmental toxicants, and/or endocrine disruptors from the 1996 HAPs database. Because concentrations of many of these were highly correlated, we combined the chemicals into mechanistic and structural groups, calculating summary index scores. We calculated ASD risk in the upper quartiles of these group scores or individual chemical concentrations compared with below the median, adjusting for demographic factors.

RESULTS

The adjusted odds ratios (AORs) were elevated by 50% in the top quartile of chlorinated solvents and heavy metals [95% confidence intervals (CIs) , 1.1-2.1], but not for aromatic solvents. Adjusting for these three groups simultaneously led to decreased risks for the solvents and increased risk for metals (AORs for metals: fourth quartile = 1.7 ; 95% CI, 1.0-3.0 ; third quartile = 1.95 ; 95% CI, 1.2-3.1) . The individual compounds that contributed most to these associations included mercury, cadmium, nickel, trichloroethylene, and vinyl chloride.

CONCLUSIONS

Our results suggest a potential association between autism and estimated metal concentrations, and possibly solvents, in ambient air around the birth residence, requiring confirmation and more refined exposure assessment in future studies.

Nitrogen dioxide prediction in Southern California using land use regression modeling: potential for environmental health analyses

We modeled the intraurban distribution of nitrogen dioxide (NO(2)), a marker for traffic pollution, with land use regression, a promising new exposure classification technique. We deployed diffusion tubes to measure NO(2) levels at 39 locations in the fall of 2003 in San Diego County, CA, USA. At each sample location, we constructed circular buffers in a geographic information system and captured information on roads, traffic flow, land use, population and housing. Using multiple linear regression, we were able to predict 79% of the variation in NO(2) levels with four variables: traffic density within 40-300 m of the sampling location, traffic density within 300-1000 m, length of road within 40 m and distance to the Pacific coast. Applying this model to validation samples showed that the model predicted NO(2) levels within, on average, 2.1 p.p.b for 12 training sites initially excluded from the model. Our evaluation of this land use regression model showed that this method had excellent prediction and robustness in a North American context. These models may be useful tools in evaluating health effects of long-term exposure to traffic-related pollution.

Correlating agricultural use of organophosphates with outdoor air concentrations: a particular concern for children

For the organophosphate pesticide chlorpyrifos, median inhalation noncancer, acute children's exposures in agricultural communities are elevated above reference doses; for diazinon, similar exposures are nearly elevated. We used multivariate linear regression analysis to examine the temporal and spatial associations between agricultural use and measured air concentrations of chlorpyrifos, chlorpyrifos oxon, diazinon, and malathion. Agricultural use within a 3-mile radius on the monitoring day and use on the 2-4 prior days were significantly associated with air concentrations (p < 0.01) for all analytes except malathion; chlorpyrifos oxon showed the strongest association (p < 0.0001). In the final models, which included weather parameters, the proportion of variance (r2, adjusted for the number of model variables) for all analytes ranged from 0.28 (p < 0.01) for malathion to 0.65 (p < 0.0001) for diazinon. Recent cellular, animal, and human evidence of toxicity, particularly in newborns, supports the public health concern indicated by initial risk estimates. Agricultural applications of organophosphates and their oxon products may have substantial volatization and off-field movement and are a probable source of exposures of public health concern.

Agricultural pesticides and lymphoproliferative childhood cancer in California

OBJECTIVES

This study evaluated whether the rates of lymphoproliferative malignancies among children are elevated in areas of intensive agricultural pesticide use in the state of California in the United States.

METHODS

The study included all newly diagnosed, statewide cases of childhood lymphoma and acute lymphoblastic leukemia in 1988-1994 among children aged <15 years. Of the 2642 cases (over 6.6 million children in California and 46 million child-years of observation) during this period, 2570 (97.3%) could be successfully geocoded for the analyses. An a priori classification of the >850 chemical agents reported in use during the study was developed by assigning the agents to eight chemical groupings of interest and identifying seven individual high-use agents with high potential toxicity. Rate ratios for neighborhood (block group) levels of pesticide use were estimated with a Poisson regression and adjustment for age, race and ethnicity, and gender.

RESULTS

The rates of childhood lymphoma and leukemia were not generally higher in high pesticide-use areas. Those of Hodgkin's disease, although based on small numbers (N=258), were slightly elevated in the areas with the highest use of several pesticide groupings.

CONCLUSIONS

The generally null results in this study systematically examining the risk relationships for residential proximity to agricultural pesticide use stand in contrast to existing epidemiologic literature suggesting elevated childhood cancer risks from reported household pesticide use. These differences may be due to different chemical agents or to differences in indoor versus outdoor exposure potential or both. Future studies should use refined methods that better characterize the exposure potential for children to these agents.

Community exposures to airborne agricultural pesticides in California: ranking of inhalation risks

We assessed inhalation risks to California communities from airborne agricultural pesticides by probability distribution analysis using ambient air data provided by the California Air Resources Board and the California Department of Pesticide Regulation. The pesticides evaluated include chloropicrin, chlorothalonil, chlorpyrifos, S,S,S-tributyl phosphorotrithioate, diazinon, 1,3-dichloropropene, dichlorvos (naled breakdown product), endosulfan, eptam, methidathion, methyl bromide, methyl isothiocyanate (MITC; metam sodium breakdown product), molinate, propargite, and simazine. Risks were estimated for the median and 75th and 95th percentiles of probability (50, 25, and 5% of the exposed populations). Exposure estimates greater than or equal to noncancer reference values occurred for 50% of the exposed populations (adults and children) for MITC subchronic and chronic exposures, methyl bromide subchronic exposures (year 2000 monitoring), and 1,3-dichloropropene subchronic exposures (1990 monitoring). Short-term chlorpyrifos exposure estimates exceeded the acute reference value for 50% of children (not adults) in the exposed population. Noncancer risks were uniformly higher for children due to a proportionately greater inhalation rate-to-body weight ratio compared to adults and other factors. Target health effects of potential concern for these exposures include neurologic effects (methyl bromide and chlorpyrifos) and respiratory effects (1,3-dichloropropene and MITC). The lowest noncancer risks occurred for simazine and chlorothalonil. Lifetime cancer risks of one-in-a-million or greater were estimated for 50% of the exposed population for 1,3-dichloropropene (1990 monitoring) and 25% of the exposed populations for methidathion and molinate. Pesticide vapor pressure was found to be a better predictor of inhalation risk compared to other methods of ranking pesticides as potential toxic air contaminants.