Rudolph P. Rull

Outdoor air pollution and uncontrolled asthma in the San Joaquin Valley, California

Background The San Joaquin Valley (SJV) in California ranks among the worst in the USA in terms of air quality, and its residents report some of the highest rates of asthma symptoms and asthma-related emergency department (ED) visits and hospitalisations in California. Using California Health Interview Survey data, the authors examined associations between air pollution and asthma morbidity in this region. Methods Eligible subjects were SJV residents (2001 California Health Interview Survey) who reported physician-diagnosed asthma (n=1502, 14.6%). The authors considered two outcomes indicative of uncontrolled asthma: (1) daily or weekly asthma symptoms and (2) asthma-related ED visits or hospitalisation in the past year. Based on residential zip code, subjects were assigned annual average concentrations of ozone, PM10 and PM2.5 for the 1-year period prior to the interview date from their closest government air monitoring station within an 8 km (5 miles) radius. Results Adjusting for age, gender, race/ethnicity, poverty level and insurance status, the authors observed increased odds of experiencing daily or weekly asthma symptoms for ozone, PM10 and PM2.5 (ORozone 1.23, 95% CI 0.94 to 1.60 per 10 ppb; ORPM10 1.29, 95% CI 1.05 to 1.57 per 10 μg/m3; and ORPM2.5 1.82; 95% CI 1.11 to 2.98 per 10 μg/m3). The authors also observed increased odds of asthma-related ED visits or hospitalisations for ozone (OR 1.49, 95% CI 1.05 to 2.11 per 10 ppb) and a 29% increase in odds for PM10 (OR 1.29, 95% CI 0.99 to 1.69 per 10 μg/m3). Conclusions Overall, these findings suggest that individuals with asthma living in areas of the SJV with high ozone and particulate pollution levels are more likely to have frequent asthma symptoms and asthma-related ED visits and hospitalisations.

Determinants of Agricultural Pesticide Concentrations in Carpet Dust

Background: Residential proximity to agricultural pesticide applications has been used as a surrogate for exposure in epidemiologic studies, although little is known about the relationship with levels of pesticides in homes. Objective: We identified determinants of concentrations of agricultural pesticides in dust. Methods: We collected samples of carpet dust and mapped crops within 1,250 m of 89 residences in California. We measured concentrations of seven pesticides used extensively in agriculture (carbaryl, chlorpyrifos, chlorthal-dimethyl, diazinon, iprodione, phosmet, and simazine). We estimated use of agricultural pesticides near residences from a statewide database alone and by linking the database with crop maps. We calculated the density of pesticide use within 500 and 1,250 m of residences for 180, 365, and 730 days before collection of dust and evaluated relationships between agricultural pesticide use estimates and pesticide concentrations in carpet dust. Results: For five of the seven pesticides evaluated, residences with use of agricultural pesticides within 1,250 m during the previous 365 days had significantly higher concentrations of pesticides than did residences with no nearby use. The highest correlation with concentrations of pesticides was generally for use reported within 1,250 m of the residence and 730 days before sample collection. Regression models that also accounted for occupational and home use of pesticides explained only a modest amount of the variability in pesticide concentrations (4–28%). Conclusions: Agricultural pesticide use near residences was a significant determinant of concentrations of pesticides in carpet dust for five of seven pesticides evaluated.

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 childs 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.

Environmental Public Health Tracking of Childhood Asthma Using California Health Interview Survey, Traffic, and Outdoor Air Pollution Data

Background Despite extensive evidence that air pollution affects childhood asthma, state-level and national-level tracking of asthma outcomes in relation to air pollution is limited. Objectives Our goals were to evaluate the feasibility of linking the 2001 California Health Interview Survey (CHIS), air monitoring, and traffic data; estimate associations between traffic density (TD) or outdoor air pollutant concentrations and childhood asthma morbidity; and evaluate the usefulness of such databases, linkages, and analyses to Environmental Public Health Tracking (EPHT). Methods We estimated TD within 500 feet of residential cross-streets of respondents and annual average pollutant concentrations based on monitoring station measurements. We used logistic regression to examine associations with reported asthma symptoms and emergency department (ED) visits/hospitalizations. Results Assignment of TD and air pollution exposures for cross-streets was successful for 82% of children with asthma in Los Angeles and San Diego, California, Counties. Children with asthma living in high ozone areas and areas with high concentrations of particulate matter < 10 μm in aerodynamic diameter experienced symptoms more frequently, and those living close to heavy traffic reported more ED visits/hospitalizations. The advantages of the CHIS for asthma EPHT include a large and representative sample, biennial data collection, and ascertainment of important socio-demographic and residential address information. Disadvantages are its cross-sectional design, reliance on parental reports of diagnoses and symptoms, and lack of information on some potential confounders. Conclusions Despite limitations, the CHIS provides a useful framework for examining air pollution and childhood asthma morbidity in support of EPHT, especially because later surveys address some noted gaps. We plan to employ CHIS 2003 and 2005 data and novel exposure assessment methods to re-examine the questions raised here.

Residential Traffic Density and Childhood Leukemia Risk

Background: Exposures to carcinogenic compounds from vehicle exhaust may increase childhood leukemia risk, and the timing of this exposure may be important. Methods: We examined the association between traffic density and childhood leukemia risk for three time periods: birth, time of diagnosis, and lifetime average, based on complete residential history in a case-control study. Cases were rapidly ascertained from participating hospitals in northern and central California between 1995 and 2002. Controls were selected from birth records, individually matched on age, sex, race, and Hispanic ethnicity. Traffic density was calculated by estimating total vehicle miles traveled per square mile within a 500-foot (152 meter) radius area around each address. We used conditional logistic regression analyses to account for matching factors and to adjust for household income. Results: We included 310 cases of acute lymphocytic leukemias (ALL) and 396 controls in our analysis. The odds ratio for ALL and residential traffic density above the 75th percentile, compared with subjects with zero traffic density, was 1.17 [95% confidence interval (95% CI), 0.76-1.81] for residence at diagnosis and 1.11 (95% CI, 0.70-1.78) for the residence at birth. For average lifetime traffic density, the odds ratio was 1.24 (95% CI, 0.74-2.08) for the highest exposure category. Conclusions: Living in areas of high traffic density during any of the exposure time periods was not associated with increased risk of childhood ALL in this study. (Cancer Epidemiol Biomarkers Prev 2008;17(9):2298–301)

Validation of self-reported proximity to agricultural crops in a case–control study of neural tube defects

Self-reported perinatal exposures to chemicals or pollutant sources in case–control studies of birth defects may be inaccurate due to misreporting among mothers. In a case–control study of neural tube defects delivered in California in 1987–1988, mothers of case and control infants were asked whether they lived within 0.25 mile (400 m) of agricultural crops. Responses were compared against a gold standard derived from historical agricultural land-use survey maps. The odds ratio for self-reported proximity to any crops (1.62, 95% confidence interval: 1.08, 2.43) appeared to be positively biased compared with the estimate for map-based proximity (1.17, 95% confidence interval: 0.79, 1.71). This pattern was also observed for proximity to specific crops such as nonpermanent and orchard crops. For vineyards, however, we observed an increased risk associated with map-based proximity (odds ratio=2.45, 95% confidence interval: 1.08, 5.58) but not with self-reported proximity (1.09, 95% confidence interval: 0.51, 2.34). The sensitivity of self-reported proximity to any crops was greater for case (65.7%) than control mothers (50.0%) while specificity was about the same for case and control mothers (87.5 vs. 89.3%), suggesting that control mothers under-reported proximity to crops. Differential reporting was also observed between geographic regions, urban and rural residents, and across levels of maternal employment and education. These results suggest differential reporting between case and control mothers as well as an influence from maternal demographic characteristics on reporting accuracy.

Determinants and Within-Person Variability of Urinary Cadmium Concentrations among Women in Northern California

Background: Cadmium (Cd) is a toxic metal associated with increased morbidity and mortality. Urinary Cd (U-Cd) concentration is considered a biomarker of long-term exposure. Objectives: Our objectives were to evaluate the within-person correlation among repeat samples and to identify predictors of U-Cd concentrations. Methods: U-Cd concentrations (micrograms per liter) were measured in 24-hr urine samples collected from 296 women enrolled in the California Teachers Study in 2000 and a second 24-hr sample collected 3–9 months later from 141 of the participants. Lifestyle and sociodemographic characteristics were obtained via questionnaires. The Total Diet Study database was used to quantify dietary cadmium intake based on a food frequency questionnaire. We estimated environmental cadmium emissions near participants’ residences using a geographic information system. Results: The geometric mean U-Cd concentration was 0.27 µg/L and the range was 0.1–3.6 µg/L. The intraclass correlation among repeat samples from an individual was 0.50. The use of a single 24-hr urine specimen to characterize Cd exposure in a case–control study would result in an observed odds ratio of 1.4 for a true odds ratio of 2.0. U-Cd concentration increased with creatinine, age, and lifetime pack-years of smoking among ever smokers or lifetime intensity-years of passive smoking among nonsmokers, whereas it decreased with greater alcohol consumption and number of previous pregnancies. These factors explained 42–44% of the variability in U-Cd concentrations. Conclusion: U-Cd levels varied with several individual characteristics, and a single measurement of U-Cd in a 24-hr sample did not accurately reflect medium- to long-term body burden.

Reproductive factors, exogenous hormones, and pancreatic cancer risk in the CTS.

Female steroid hormones are hypothesized to play a protective role in pancreatic cancer risk. However, results from epidemiologic studies that examined hormone-related exposures have been inconsistent. The California Teachers Study is a cohort study of female public school professionals that was established in 1995-1996. Of the 118,164 eligible study participants, 323 women were diagnosed with incident invasive pancreatic cancer through December 31, 2009. Multivariable Cox proportional hazards regression methods were used to estimate hazard ratios and 95% confidence intervals for the association of pancreatic cancer risk with reproductive factors and exogenous hormone use. Current users of estrogen-only therapy at baseline (1995-1996) had a lower risk of pancreatic cancer than did participants who had never used hormone therapy (hazard ratio = 0.59, 95% confidence interval: 0.42, 0.84). Use of estrogen-plus-progestin therapy was not associated with the risk of pancreatic cancer. A longer duration of oral contraceptive use (≥10 years of use compared with never use) was associated with an increased risk of cancer (hazard ratio = 1.72, 95% confidence interval: 1.19, 2.49). Reproductive factors, including age at menarche, parity, breastfeeding, and age at menopause, were not associated with pancreatic cancer risk. Our results suggest that increased estrogen exposure through estrogen-only therapy may reduce pancreatic cancer risk in women.

Assessment of environmental exposures from agricultural pesticides in childhood leukaemia studies: challenges and opportunities

Pesticides are ubiquitous in environments of many rural communities due to drift from agricultural applications and home/garden use. Studies of childhood leukaemia predominantly relied on retrospective pesticide exposure assessment and parental recall of use or proximity to fields or pesticide applications. Sample size requirements mostly preclude the collection of individual-level exposure information, biomarkers or environmental measurements of pesticides prospectively in cohorts. Yet such measures can be used in nested case-control approaches or for validating exposure models that can be applied to large populations. Recently developed models incorporate geographic information system technology and environmental databases of pesticide and/or crop data to assess exposure. Models developed in California to estimate residential exposures are presented by linking addresses to agricultural pesticide application data and land-use maps. Results from exposure validation and simulation studies and exposure measurement error issues are discussed.

Nativity and papillary thyroid cancer incidence rates among Hispanic women in California.

Overall, the incidence of papillary thyroid cancer in Hispanic women residing in the United States (US) is similar to that of non‐Hispanic white women. However, little is known as to whether rates in Hispanic women vary by nativity, which may influence exposure to important risk factors.