Findings from Exposure Studies

Click on the study name below to see findings, or scroll down the page.

Studies in Farmworkers

  • Field-Based Intervention
  • Home-Based Intervention
  • Occupational Behaviors Intervention

Studies in Pregnant and Perinatal Women

  • Maternal Organophosphate Pesticide Metabolites in Urine
  • Organophosphate Pesticide Exposure Modeling
  • Pilot Study of Persistent and Non-Persistent Pesticides and Other Chemicals in Breast Milk
  • Persistent Organic Pollutants and Duration of Lactation
  • Maternal Exposure to Organochlorine Pesticides
  • Maternal PBDE Flame Retardant Exposure Studies

Studies in Children

  • Time Activity Analysis
  • Child Urinary Organophosphate Pesticide Metabolites
  • Infant-Toddler Exposure Study
  • Child PBDE Flame Retardant Exposure Studies

Studies of Chemicals in House Dust

  • Pesticides Measured in House Dust
  • Pre-Formed Organophosphate Metabolites in House Dust
  • PBDE Flame Retardants in House Dust

Study Findings:

Findings from Studies in Farmworkers:

Field-Based Intervention Study Findings

  • Clothing and gloves reduced observed levels of the organophosphate (OP) pesticide malathion on the skin and hands of strawberry harvesters. (Go to publication)
  • Wearing gloves significantly reduced urinary malathion metabolites in strawberry harvesters. (Go to publication)
  • Workers who ate strawberries in the field had higher malathion metabolite levels in urine compared to workers who did not. (Go to publication)
  • Study findings suggest that:
    • Wearing gloves and coveralls reduces pesticide exposure to strawberry pickers.
    • Removing work clothes before leaving the fields could reduce transport of pesticides into worker homes and cars.
    • Workers need to be better informed about exposure from eating strawberries in the field.

Home-Based Intervention Study Findings

  • We evaluated a worksite intervention intended to improve farmworkers’ behaviors during and after work to reduce occupational and take-home pesticide exposures. (Go to publication)
  • Workers received warm water and soap for hand washing, gloves, coveralls, and education. (Go to publication)
  • Self-reported assessments before and after the intervention revealed that glove use, wearing clean work clothes, and hand washing practices increased significantly among farmworkers. (Go to publication)

Occupational Behaviors Intervention Study Findings

  • We studied the relationship between behaviors promoted through the US EPA Worker Protection Standard and other programs and agricultural pesticide exposures in 73 strawberry fieldworkers employed in Monterey County, California. (Go to publication)
  • Wearing recommended clothing, clean work clothes, and the combination of hand washing with soap and wearing gloves were associated with decreases in malathion metabolite levels in urine. (Go to publication)
  • Despite these protective behaviors, however, participants had significantly higher levels of exposure as compared with a U.S. national reference sample of adults. (Go to publication)
  • Study findings suggest that:
    • Interventions that facilitate compliance with protective behaviors may be effective in decreasing fieldworkers’ pesticide exposures.
    • However, further efforts are needed to reduce the exposure disparities experienced by farmworkers and decrease the potential for “take home” exposures to farmworkers’ families.

Findings from Studies in Pregnant and Perinatal Women:

Maternal Organophosphate Pesticide Metabolites in Urine

  • The CHAMACOS cohort of pregnant women have levels of organophosphate (OP) pesticide metabolite levels in urine 30-40% higher than U.S. national reference levels reported for women of child-bearing age (18-40 yrs old) by NHANES.  (Go to publication)
  • Based on cumulative OP pesticide dose estimates, 14.8% of pregnant women in the CHAMACOS cohort may exceed health-based exposure benchmarks. (Go to publication)
  • We also measured 34 metabolites of current-use pesticides and other precursor compounds in urine samples collected from women twice during pregnancy. (Go to publication)
  • Detected metabolites may be related to home or agricultural pesticide use in the Salinas Valley, household products, and other sources of chlorinated phenols. (Go to publication)
  • More than 78% of CHAMACOS women had detectable levels of at least one OP pesticide-specific metabolite, and > 30% had two or more. (Go to publication)
  • The 95th percentile values of six of the most commonly detected compounds were significantly higher among the CHAMACOS women compared to U.S. national reference levels for pregnant women after controlling for age, race, socioeconomic status, and smoking. (Go to publication)
  • Findings suggest that the CHAMACOS cohort has an additional burden of pesticide exposure compared with the national sample, possibly from living and/or working in an agricultural area(Go to publication)

Organophosphate Pesticide Exposure Modeling

  • Biomarker comparisons and model results showed that women in the CHAMACOS cohort have a slightly but significantly higher intake of OP pesticides compared to women in the US general population as reported in NHANES. (Go to publication)
  • Results from this comparison suggest that diet is the common and dominant exposure pathway in both populations. (Go to publication)

Pilot Study of Persistent and Non-Persistent Pesticides and Other Chemicals in Breast Milk

  • We measured non-persistent and persistent pesticides and polychlorinated biphenyl (PCB) congeners in human milk samples collected from women residing in Salinas, CA and the San Francisco Bay Area. (Go to publication)
  • Median concentrations for 21 urban and 13 agricultural women were reported. (Go to publication)
  • Results suggest that neonates and young children may be exposed to persistent and non-persistent pesticides and PCBs via breast milk. (Go to publication)

Persistent Organic Pollutants and Duration of Lactation

  • We measured select organochlorines and polychlorinated biphenyls (PCBs) in serum from 366 pregnant women of the CHAMACOS cohort and assessed breastfeeding duration by questionnaire. (Go to publication)
  • We found no associations between estrogenic persistent organic pollutants (POPs) with shortened lactation duration; associations were found, however, between two potentially estrogenic POPs (p, p’-DDE & PCB-52) with lengthened lactation duration. (Go to publication)
  • Estrogenic POPs were not associated with shortened lactation duration, but may be associated with longer lactation duration. (Go to publication)

Maternal Exposure to Organochlorine Pesticides

  • We measured organochlorine pesticides in serum from 426 low-income pregnant Latina women living in an agricultural community in California. (Go to publication)
  • Detection frequencies were 94% to 100%. (Go to publication)
  • Median levels of p,p’-DDE, p,p’-DDT, beta-HCH and HCB were significantly higher than United States population levels. (Go to publication)
  • Multivariate analyses 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. (Go to publication)
  • Lactation history and recent weight gain were negatively associated with serum levels of some, but not all OC compounds studied. (Go to publication)
  • 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. (Go to publication)

Maternal PBDE Flame Retardant Exposure Studies

  • We analyzed PBDE levels from a subset of the CHAMACOS cohort of recent immigrants (n=24 pregnant women). (Go to publication)
  • We found that time residing in the U.S. was associated with increased PBDE levels, albeit not significantly. (Go to publication)
  • We expanded our analysis to report serum PBDE levels in 416 pregnant women, and we identify important determinants of exposure. (Go to publication)
  • The most frequently detected congeners in pregnant women’s serum were BDE-47, -99, -100 and -153, all components of the penta mixture, detected in 100% of samples. (Go to publication)
  • Women’s total PBDE levels increased significantly with each additional year residing in the U.S., after adjustment for prepregnancy BMI, weight gain during pregnancy, and SES. (Go to publication)
  • Having ≥3 pieces of stuffed furniture in the home was also associated with increases in women’s serum PBDE levels. (Go to publication)
  • Findings suggest PBDE indoor contamination in California homes is contributing to human exposures.  (Go to publication)

Findings from Studies in Children:

Time Activity Analysis

  • Co-investigators quantified exposure-prone behaviors in young children using videotaping techniques. (Go to publication 1)
  • The median hand-to-mouth frequency was 15.2 events/hr and the median object-to-mouth frequency was 27.2 events/hr. (Go to publication 1)
  • Boys had higher contact frequencies while girls had longer contact durations. (Go to publication 1)
  • Differences indicate factors such as age and gender should be accounted for when conducting exposure assessments. (Go to publication 1)
  • Contact frequencies in this study were higher than current US EPA recommendations, calling into question their protective value for infants and toddlers. (Go to publication 1)
  • The Cumulative Aggregate Simulation of Exposure (CASE) model, was then used to estimate residential non-dietary organophosphate pesticide exposure (i.e., inhalation, dermal, and nondietary ingestion) to California farmworker children and evaluate the micro-activity approach. (Go to publication)
  • Model results demonstrated that simulations can be used to identify at-risk children and target intervention strategies. (Go to publication)

1. Beamer P, Key ME, Ferguson AC, Canales RA, Auyeung W, Leckie JO. Quantified activity pattern data from 6 to 27-month-old farmworker children for use in exposure assessment. Environ Res. 2008 Oct;108(2):239-46. Epub 2008 Aug 23.

Child Urinary Organophosphate Pesticide Metabolites

  • Urinary metabolite levels of OP pesticides in 6 to 24-month-old children increase with age, and eating more fruits and vegetables. (Go to publication)

Infant-Toddler Exposure Study

  • Pesticides were detected more frequently in house dust, surface wipes, and clothing than other media. (Go to publication)
  • Chlorpyrifos, diazinon, chlorthal-dimethyl, and cis- and trans-permethrin detected in 90-100% of house dust, surface wipes, and clothing samples. (Go to publication)
  • Pesticide residues on clothing (union suits and socks) were consistently higher in the older group of children (21-27 months) compared to the younger children (5-11 months). (Go to publication)
  • Child Activity Timeline, a low-literacy instrument based on pictures, was successfully used by participants and has been implemented in recent studies. (Go to publication)
  • Study findings suggest that:
    • Higher concentrations of the most frequently detected analytes on the clothing of the older age group may be attributed to the fact that toddlers are more actively walking, running, crawling, and playing than younger children, and are thus potentially more exposed to pesticide residues from residential surfaces.

Child PBDE Flame Retardant Exposure Studies

  • We analyzed PBDE levels in blood collected from 7-year old children of the CHAMACOS cohort (n=272).  (Publication Submitted*)
  • The most frequently detected PBDE congeners in child serum were BDEs-47, -99, -100 and -153, all of which were measured in >99% of samples.  (Publication Submitted*)
  • We examined associations between child total PBDE levels and determinants of exposure. (Publication Submitted*)
  • 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. (Publication Submitted*)
  • Child BMI was inversely associated with serum PBDE levels. (Publication Submitted*)
  • We compared child PBDE levels among 7-year old Mexican-American children of the CHAMACOS cohort (n=264) with levels in 5-year old Mexican children living in areas where most CHAMACOS mothers had originated (n=283).  (Go to publication)
  • On average, PBDE serum concentrations in the California Mexican-American children were seven times higher than concentrations in the children living in Mexico and three times higher than their mothers’ levels during pregnancy. (Go to publication)
  • Our findings confirm that exposure to the penta-BDE mixture is ongoing, and that Mexican-American children living in California are experiencing higher PBDE exposure from their environment compared to children sampled from the general U.S. population.  (Go to publication)
  • As PBDEs are being phased out and replaced by other flame retardants, the health consequences of these chemical replacements should be investigated and weighed against their purported fire safety benefits. (Go to publication)

* Bradman A, Castorina R, Sjödin A, Fenster L, Jones RS, Harley KG, Chevrier J, Holland NT, Brenda Eskenazi. Factors Associated with Serum Polybrominated Diphenyl Ether (PBDE) Levels among School-Age Children in the CHAMACOS Cohort. Environ Sci Tech.  Submitted, 2011.

Findings from Studies of Chemicals in House Dust:

Pesticides Measured in House Dust

  • Of 22 pesticides measured in dust samples collected from Salinas Valley homes, permethrins and the OP pesticide chlorpyrifos were present in the highest amounts. (Go to publication)
  • Nearby agricultural use of chlorpyrifos and other more persistent pesticides was associated with higher levels in house dust. (Go to publication)
  • Follow-up studies suggest levels of chlorpyrifos and diazinon declined, possibly related to the phase-out of these pesticides for home use. (Go to publication)
  • In a 2006 study in low-income homes from urban and agricultural communities, we compared house dust levels of agricultural and residential-use pesticides. (Go to publication)
  • We collected up to two dust samples 5-8 days apart from each of 13 urban homes in Oakland, CA and 15 farmworker homes in Salinas, CA, an agricultural community (54 samples total).  (Go to publication)
  • We measured 22 insecticides including OP and pyrethroid pesticides, one phthalate herbicide (chlorthal-dimethyl), one dicarboximide fungicide (iprodione), and one pesticide synergist (piperonyl butoxide).  (Go to publication)
  • More than half of the households reported applying pesticides indoors. (Go to publication)
  • Analytes frequently detected in both locations included chlorpyrifos, diazinon, permethrin, allethrin, cypermethrin, and piperonyl butoxide; no differences in concentrations or loadings were observed between locations for these analytes. (Go to publication)
  • Chlorthal-dimethyl was detected solely in farmworker homes, suggesting contamination due to regional agricultural use. (Go to publication)
  • Concentrations in samples collected 5-8 days apart in the same home were strongly correlated for the majority of the frequently detected analytes.  (Go to publication)
  • The frequent pesticide use reported and high detection of several home-use pesticides in house dust suggests that families would benefit from integrated pest management strategies to control pests and minimize current and future exposures. (Go to publication)
  • In support of planning efforts for the National Children’s Study, we tested methods for collecting dust and other environmental media from the homes of farmworker children aged 5-27 months. (Go to publication)
  • We measured 29 common agricultural and home use pesticides in multiple exposure media samples. (Go to publication)
  • Pesticides were detected more frequently in house dust, surface wipes, and clothing than other media, with chlorpyrifos, diazinon, chlorthal dimethyl, and cis- and trans-permethrin detected in 90% to 100% of samples. (Go to publication)
  • Levels of four of these five pesticides were positively correlated among the house dust, sock, and union suit samples. (Go to publication)

Pre-formed Organophosphate Metabolites in House Dust

  • To establish the presence of OP pesticide metabolites in environmental and food media, we developed analytical methods to measure six dialkylphosphate (DAPs) metabolites in dust and orange juice. (Go to publication)
  • The limits of detection (LOD) ranged from 2.8-10.4 ng/ g in dust and 0.2-3.0 ng/ mL juice. (Go to publication)
  • DAP metabolites were detected in 80% of the dust samples tested. (Go to publication)
  • In addition, we collected dust samples from homes in farmworker and urban communities in California (40 homes total, n=79 samples) urine samples from resident children ages 3-6 years. (Publication In Press**)
  • We measured six DAPs in all samples (DEP, DETP, DEDTP, DMP, DMTP, and DMDTP) and eight DAP-devolving OP pesticides in a subset of dust samples (n=54). (Publication In Press**)
  • DAPs were detected in dust with DEP being the most frequently detected (>60%). (Publication In Press**)
  • DEP dust concentrations did not significantly differ between communities; nor were concentrations significantly correlated with dust concentrations of chlorpyrifos and diazinon. (Publication In Press**)
  • Finally, estimated non-dietary ingestion intake from DEP in dust was found to be < 5% of the dose calculated from DEP levels in urine, suggesting that ingestion of dust is not a significant source of DAPs in urine if they are excreted unchanged. (Publication In Press**)

** Quirós-Alcalá L, Bradman A, Smith KD, Weeraseker G, Odetokuns M, Barr DB,  Nishioka M,  Castorina R, Hubbard AE, Nicas M, S. Hammond K, McKone TE,  Eskenazi B. Organophosphorous pesticide breakdown products in house dust and children’s urine. J Expo Sci Environ Epidemiol. In Press, 2011.

PBDE Flame Retardants in House Dust

  • We collected dust samples, several days apart, from low-income California households in the urban community of Oakland (n=13 homes) and the agricultural community of Salinas (n=15 homes). (Go to publication)
  • We measured BDE-47, BDE-99 and BDE-100, the major constituents of the penta-PBDE flame retardant formulation commonly used in furniture. (Go to publication)
  • All three PBDE congeners were detected in every sample. (Go to publication)
  • Maximum concentrations for BDE-47 and BDE-99 were the highest reported to date. (Go to publication)

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