Association of ambient air pollution and pesticide mixtures on respiratory inflammatory markers in agricultural communities.

Air pollution exposure is associated with adverse respiratory health outcomes. Evidence from occupational and community-based studies also suggests agricultural pesticides have negative health impacts on respiratory health. Although populations are exposed to multiple inhalation hazards simultaneously, multidomain mixtures (e.g. environmental and chemical pollutants of different classes) are rarely studied. We investigated the association of ambient air pollution-pesticide exposure mixtures with urinary leukotriene E4 (LTE4), a respiratory inflammation biomarker, for 75 participants in four Central California communities over two seasons. Exposures included three criteria air pollutants estimated via the Community Multiscale Air Quality model (fine particulate matter, ozone, and nitrogen dioxide) and urinary metabolites of organophosphate (OP) pesticides (total dialkyl phosphates (DAPs), total diethyl phosphates (DE), and total dimethyl phosphates (DM)). We implemented multiple linear regression models to examine associations in single pollutant models adjusted for age, sex, asthma status, occupational status, household member occupational status, temperature, and relative humidity, and evaluated whether associations changed seasonally. We then implemented Bayesian kernel machine regression (BKMR) to analyse these criteria air pollutants, DE, and DM as a mixture. Our multiple linear regression models indicated an interquartile range (IQR) increase in total DAPs was associated with an increase in urinary LTE4 in winter (ß: 0.04, 95% CI: [0.01, 0.07]). Similarly, an IQR increase in total DM was associated with an increase in urinary LTE4 in winter (ß:0.03, 95% CI: [0.004, 0.06]). Confidence intervals for all criteria air pollutant effect estimates included the null value. BKMR analysis revealed potential non-linear interactions between exposures in our air pollution-pesticide mixture, but all confidence intervals contained the null value. Our analysis demonstrated a positive association between OP pesticide metabolites and urinary LTE4 in a low asthma prevalence population and adds to the limited research on the joint effects of ambient air pollution and pesticides mixtures on respiratory health.

Factors Associated with Levels of Organophosphate Pesticides in Household Dust in Agricultural Communities.

Organophosphate (OP) pesticides are associated with numerous adverse health outcomes. Pesticide use data are available for California from the Pesticide Use Report (PUR), but household- and individual-level exposure factors have not been fully characterized to support its refinement as an exposure assessment tool. Unique exposure pathways, such as proximity to agricultural operations and direct occupational contact, further complicate pesticide exposure assessment among agricultural communities. We sought to identify influencing factors of pesticide exposure to support future exposure assessment and epidemiological studies. Household dust samples were collected from 28 homes in four California agricultural communities during January and June 2019 and were analyzed for the presence of OPs. Factors influencing household OPs were identified by a data-driven model via best subsets regression. Key factors that impacted dust OP levels included household cooling strategies, secondary occupational exposure to pesticides, and geographic location by community. Although PUR data demonstrate seasonal trends in pesticide application, this study did not identify season as an important factor, suggesting OP persistence in the home. These results will help refine pesticide exposure assessment for future studies and highlight important gaps in the literature, such as our understanding of pesticide degradation in an indoor environment.

The Androgen Receptor Supports Tumor Progression After the Loss of Ovarian Function in a Preclinical Model of Obesity and Breast Cancer.

The androgen receptor (AR) has context-dependent roles in breast cancer growth and progression. Overall, high tumor AR levels predict a favorable patient outcome, but several studies have established a tumor promotional role for AR, particularly in supporting the growth of estrogen receptor positive (ER-positive) breast cancers after endocrine therapy. Our previous studies have demonstrated that obesity promotes mammary tumor progression after ovariectomy (OVX) in a rat model of postmenopausal breast cancer. Here, we investigated a potential role for AR in obesity-associated post-OVX mammary tumor progression following ovarian estrogen loss. In this model, we found that obese but not lean rats had nuclear localized AR in tumors that progressed 3 weeks after OVX, compared to those that regressed. AR nuclear localization is consistent with activation of AR-dependent transcription. Longer-term studies (8 weeks post-OVX) showed that AR nuclear localization and expression were maintained in tumors that had progressed, but AR expression was nearly lost in tumors that were regressing. The anti-androgen enzalutamide effectively blocked tumor progression in obese rats by promoting tumor necrosis and also prevented the formation of new tumors after OVX. Neither circulating nor mammary adipose tissue levels of the AR ligand testosterone were elevated in obese compared to lean rats; however, IL-6, which we previously reported to be higher in plasma from obese versus lean rats, sensitized breast cancer cells to low levels of testosterone. Our study demonstrates that, in the context of obesity, AR plays a role in driving ER-positive mammary tumor progression in an environment of low estrogen availability, and that circulating factors unique to the obese host, including IL-6, may influence how cancer cells respond to steroid hormones.

Short-term markers of DNA damage among roofers who work with hot asphalt.

BACKGROUND: Roofers are at increased risk for various malignancies and their occupational exposures to polycyclic aromatic hydrocarbons (PAHs) have been considered as important risk factors. The overall goal of this project was to investigate the usefulness of phosphorylated histone H2AX (γH2AX) as a short-term biomarker of DNA damage among roofers. METHODS: Blood, urine, and dermal wipe samples were collected from 20 roofers who work with hot asphalt before and after 6 h of work on Monday and Thursday of the same week (4 sampling periods). Particle-bound and gas-phase PAHs were collected using personal monitors during work hours. γH2AX was quantified in peripheral lymphocytes using flow cytometry and 8-hydroxy-2-deoxyguanosine (8-OHdG) was assessed in urine using ELISA. General linear mixed models were used to evaluate associations between DNA damage and possible predictors (such as sampling period, exposure levels, work- and life-style factors). Differences in mean biomarker and DNA damage levels were tested via ANOVA contrasts. RESULTS: Exposure measurements did not show an association with any of the urinary biomarkers or the measures of DNA damage. Naphthalene was the most abundant PAH in gas-phase, while benzo(e)pyrene was the most abundant particle-bound PAH. Post-shift levels of γH2AX and 8-OHdG were higher on both study days, when compared to pre-shift levels. Cigarette smoking was a predictor of γH2AX and urinary creatinine was a predictor of urinary 8-OHdG. Between-subject variance to total variance ratio was 35.3 % for γH2ax and 4.8 % for 8-OHdG. CONCLUSION: γH2AX is a promising biomarker of DNA damage in occupational epidemiology studies. It has a lower within-subject variation than urinary 8-OHdG and can easily be detected in large scale groups. Future studies that explore the kinetics of H2AX phosphorylation in relation to chemical exposures may reveal the transient and persistent nature of this sensitive biomarker of early DNA damage.

Particulate matter, endotoxin, and worker respiratory health on large Californian dairies.

OBJECTIVE: To assess respiratory exposures and lung function in a cross-sectional study of California dairy workers. METHODS: Exposure of 205 dairy and 45 control (vegetable processing) workers to particulate matter and endotoxin was monitored. Pre- and postshift spirometry and interviews were conducted. RESULTS: Geometric mean inhalable and PM2.5 concentrations were 812 and 35.3 µg/m3 versus 481.9 and 19.6 µg/m3, respectively, for dairy and control workers. Endotoxin concentrations were 329 EU/m3 or 1122 pmol/m3 and 13.5 EU/m3 or 110 pmol/m3, respectively, for dairy and control workers. In a mixed-effects model, forced vital capacity decreased across a work shift by 24.5 mL (95% confidence interval, -44.7 to -4.3; P = 0.018) with log10 (total endotoxin) and by 22.0 mL (95% confidence interval, -43.2 to -0.08; P = 0.042) per hour worked. CONCLUSIONS: Modern California dairy endotoxin exposures and shift length were associated with a mild acute decrease in forced vital capacity.

Development of an immunochemical detection method for atrazine-induced albumin adducts.

Atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine) is one of the most commonly used herbicides in the United States. Exposures in rodent models have led to a host of biological effects, most notably the suppression of luteinizing hormone surge. Previously, we have reported that diaminochlorotriazine (DACT), an atrazine metabolite, forms a covalent adduct with rat hemoglobin at Cys-125. In the present study, we investigated the formation of a similar covalent adduct at Cys-34 of rat and human albumins following atrazine exposure using MALDI-TOF/TOF MS and adduct-specific immunochemical detection. Using mass spectrometry, a covalent adduct with a mass of 110 Da was located on Cys-34 of albumin from rats exposed to 20, 50, 100, and 200 mg/kg atrazine as well as rat and human albumins exposed in vitro to 90 microg/mL DACT. On the basis of the formation of the adduct in vitro, the adduct structure is a dechlorinated diaminochlorotriazine. To further study this unique protein adduction, we collaborated with Strategic Biosolutions Inc. to generate a polyclonal antibody specific for the DACT adduct and report its use for immunochemical detection. We detected adduct formation in purified serum albumin samples from rats given 5, 10, 20, 50, 100, and 200 mg/kg atrazine as well as rat and human albumins exposed in vitro to 90 microg/mL DACT by using immunochemical analysis. No adducts were detected in control animals or in the in vitro controls using our immunochemical detection method. In summary, these data report the development of a novel immunochemical detection system that could provide a rapid screening methodology for the detection of atrazine in exposed human populations.

Identification of a novel hemoglobin adduct in Sprague Dawley rats exposed to atrazine.

Atrazine (2-chloro-4-[ethylamino]-6-[isopropylamino]-1,3,5-triazine) is one of the most commonly used herbicides in North America and is frequently detected in ground and surface waters. This research investigated possible covalent modifications of hemoglobin following in vivo exposures to atrazine in Sprague Dawley (SD) rats and in vitro incubations with diaminochlorotriazine. SD rats were exposed to 0, 10, 30, 100, and 300 (mg atrazine/kg)/day for 3 days via oral gavages, and blood was drawn at 0 h, 24 h, 72 h, 20 days, 1 month, and 2 months for globin analysis. Globin was purified from red blood cells, separated with high-performance liquid chromatography, and analyzed with matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS). An additional beta globin peak was seen in exposed animals during the HPLC and MALDI-TOF MS analysis with a mass 110 Da greater than the normal beta subunits. Tryptic digests of this beta peak contained a peptide of 1449.9 m/z that corresponded to a modified peptide of amino acids 121-132. Mass spectrometry sequencing of this peptide indicated a 110 Da addition to Cys-125 of the major beta globin chain, which corresponds to a nucleophilic substitution reaction with a diaminochlorotriazine. In vitro incubations of SD globin and diaminochlorotriazine also resulted in a peptide of 1449.6 m/z that was identical in sequence to the modified peptide seen in the in vivo digest, confirming the nucleophilic substitution mechanism of adduct formation. Exposures of SD rats to atrazine results in formation of an adduct that is easily detected and provides an analytical model for detection of triazine adducts in other macromolecules with sulfhydryl functional groups.