Bio

Academic Appointments


Administrative Appointments


  • Consulting Assistant Professor, Health Research & Policy, Stanford School of Medicine (2006 - Present)
  • Research Scientist, Cancer Prevention Institute of California (2006 - Present)
  • Research Scientist, Impact Assessment, Inc.; California Department of Health Services (2005 - 2006)
  • Assistant Researcher, Center for Health Policy Research, University of California, Los Angeles (2004 - 2005)

Professional Education


  • Ph.D., University of California, Los Angeles, Epidemiology (2004)
  • M.P.H., University of California, Los Angeles, Epidemiology (1999)
  • B.A., University of California at Berkeley, Environmental Sciences (1995)

Research & Scholarship

Current Research and Scholarly Interests


Dr. Rull is an epidemiologist whose research focuses on assessing and validating exposures to hazards such as metals, pesticides, traffic emissions, and other pollutants and evaluating whether these exposures affect the risk of cancer. In his research, geographic information systems (GIS) and mapping technologies play a critical role in improving the quality of exposure assessment and linking exposures to health outcomes. Dr. Rull also employs complex statistical methods such as hierarchical regression models to estimate the effects of combinations of exposures and improve precision.

Prior to joining CPIC, Dr. Rull gained extensive experience in environmental epidemiology as a doctoral student and researcher at UCLA, where he developed a GIS-based model for assessing exposures to pesticides by linking residential locations with the locations of agricultural pesticide use and crops. His dissertation examined whether women residing near specific agricultural crop types or pesticide applications during early pregnancy increased the risk of neural tube defects. In addition, he worked on studies assessing the effects of air pollutants on frequent and severe asthma symptoms in a population of asthmatic respondents to the 2001 California Health Interview Survey.

Dr. Rull is currently conducting a study examining the effect of cadmium, a carcinogenic metal that exhibits estrogen-like activity, on the risk of breast cancer in the California Teachers Study cohort. The major sources of non-occupational exposure to cadmium include cigarette smoke, diet, and inhalation of contaminated ambient air. This study is one of the few studies that will use dietary intake, environmental exposure, and a biological marker (cadmium in urine) of exposure to develop a measure of total exposure from multiple sources.

Dr. Rull’s other research activities include a Stanford Cancer Center pilot study to identify urinary biomarkers of environmental exposure to diesel exhaust, a carcinogenic pollutant. In addition, Dr. Rull is conducting a study that will use GIS to construct geographic areas within the nine-county Greater Bay Area Cancer Registry region that will allow for the mapping and analysis of cancer incidence in areas smaller than the county. These newly defined areas will have a sufficiently large base population that will allow for more reliable estimation of cancer incidence while preserving the confidentiality of cancer cases. In collaboration with Dr. Peggy Reynolds, Dr. Rull is also working on the Northern California Childhood Leukemia Study, the largest and most comprehensive study to date of risk factors for leukemia in children, where they are using GIS to evaluate the impacts of exposures to agricultural pesticides, indoor and outdoor air pollution, and other environmental hazards.

Teaching

Graduate and Fellowship Programs


Publications

Journal Articles


  • Papillary thyroid cancer incidence rates vary significantly by birthplace in Asian American women CANCER CAUSES & CONTROL Horn-Ross, P. L., McClure, L. A., Chang, E. T., Clarke, C. A., Keegan, T. H., Rull, R. P., Quach, T., Gomez, S. L. 2011; 22 (3): 479-485

    Abstract

    To investigate how birthplace influences the incidence of papillary thyroid cancer among Asian American women.Birthplace- and ethnic-specific age-adjusted and age-specific incidence rates were calculated using data from the California Cancer Registry for the period 1988-2004. Birthplace was statistically imputed for 30% of cases using a validated imputation method based on age at Social Security number issuance. Population estimates were obtained from the US Census. Incidence rate ratios (IRR) and 95% confidence intervals (CI) were estimated for foreign-born vs. US-born women.Age-adjusted incidence rates of papillary thyroid cancer among Filipina (13.7 per 100,000) and Vietnamese (12.7) women were more than double those of Japanese women (6.2). US-born Chinese (IRR = 0.48, 95% CI: 0.40-0.59) and Filipina women (IRR = 0.74, 95% CI: 0.58-0.96) had significantly higher rates than those who were foreign-born; the opposite was observed for Japanese women (IRR = 1.55, 95% CI: 1.17-2.08). The age-specific patterns among all foreign-born Asian women and US-born Japanese women showed a slow steady increase in incidence until age 70. However, among US-born Asian women (except Japanese), substantially elevated incidence rates during the reproductive and menopausal years were evident.Ethnic- and birthplace-variation in papillary thyroid cancer incidence can provide insight into the etiology of this increasingly common and understudied cancer.

    View details for DOI 10.1007/s10552-010-9720-5

    View details for Web of Science ID 000288542400015

    View details for PubMedID 21207130

  • Outdoor air pollution and uncontrolled asthma in the San Joaquin Valley, California JOURNAL OF EPIDEMIOLOGY AND COMMUNITY HEALTH Meng, Y., Rull, R. P., Wilhelm, M., Lombardi, C., Balmes, J., Ritz, B. 2010; 64 (2): 142-147

    Abstract

    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.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, PM(10) and PM(2.5) for the 1-year period prior to the interview date from their closest government air monitoring station within an 8 km (5 miles) radius.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, PM(10) and PM(2.5) (OR(ozone) 1.23, 95% CI 0.94 to 1.60 per 10 ppb; OR(PM10) 1.29, 95% CI 1.05 to 1.57 per 10 microg/m(3); and OR(PM2.5) 1.82; 95% CI 1.11 to 2.98 per 10 microg/m(3)). 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 PM(10) (OR 1.29, 95% CI 0.99 to 1.69 per 10 microg/m(3)).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.

    View details for DOI 10.1136/jech.2009.083576

    View details for Web of Science ID 000273400700012

    View details for PubMedID 20056967

  • Residential proximity to agricultural pesticide applications and childhood acute lymphoblastic leukemia ENVIRONMENTAL RESEARCH Rull, R. P., Gunier, R., Von Behren, J., Hertz, A., Crouse, V., Buffler, P. A., Reynolds, P. 2009; 109 (7): 891-899

    Abstract

    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.

    View details for DOI 10.1016/j.envres.2009.07.014

    View details for Web of Science ID 000270252600014

    View details for PubMedID 19700145

  • Assessment of environmental exposures from agricultural pesticides in childhood leukaemia studies: challenges and opportunities RADIATION PROTECTION DOSIMETRY Ritz, B., Rull, R. P. 2008; 132 (2): 148-155

    Abstract

    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.

    View details for DOI 10.1093/rpd/ncn268

    View details for Web of Science ID 000262336800007

    View details for PubMedID 18930927

  • Environmental Public Health Tracking of childhood asthma using California Health Interview Survey, traffic, and outdoor air pollution data ENVIRONMENTAL HEALTH PERSPECTIVES Wilhelm, M., Meng, Y., Rull, R. P., English, P., Balmes, J., Ritz, B. 2008; 116 (9): 1254-1260

    Abstract

    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.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).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.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 microm 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.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.

    View details for DOI 10.1289/ehp.10945

    View details for Web of Science ID 000259020100043

    View details for PubMedID 18795172

  • Residential traffic density and childhood leukemia risk CANCER EPIDEMIOLOGY BIOMARKERS & PREVENTION Von Behren, J., Reynolds, P., Gunier, R. B., Rull, R. P., Hertz, A., Urayama, K. Y., Kronish, D., Buffler, P. A. 2008; 17 (9): 2298-2301

    Abstract

    Exposures to carcinogenic compounds from vehicle exhaust may increase childhood leukemia risk, and the timing of this exposure may be important.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.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.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.

    View details for DOI 10.1158/1055-9965.EPI-08-0338

    View details for Web of Science ID 000259211400016

    View details for PubMedID 18768496

  • Are frequent asthma symptoms among low-income individuals related to heavy traffic near homes, vulnerabilities, or both? ANNALS OF EPIDEMIOLOGY Meng, Y., Wilhelm, M., Rull, R. P., English, P., Nathan, S., Ritz, B. 2008; 18 (5): 343-350

    Abstract

    To investigate whether frequent asthma symptoms (daily/weekly symptoms) can be attributed to traffic-related exposures, poverty, and/or vulnerabilities.Annual average daily vehicle traffic density (TD) within 500 feet of 2001 California Health Interview Survey respondents' residential cross streets was calculated. Logistic regression analyses were performed to evaluate the association between annual average TD and frequent asthma symptoms with income as a confounder and a modifier.After adjustment for age, sex, and race/ethnicity, a 92% increase in frequent asthma symptoms was observed among those in high TD and a 50% increase among those in medium TD compared to those in low TD. Adjustment for poverty did not change these estimates, but individuals in poverty were twice more likely to experience frequent symptoms. Furthermore, delays in care, a poor/fair health status, current/previous smoking, overweight/obese, or unemployment showed independent associations with frequent asthma symptoms. Analyses stratified on income indicated greater estimated traffic effects for asthmatics in poverty, whereas the estimates for asthmatics above the poverty level moved closer toward the null.Traffic-related exposures, poverty and vulnerabilities all increased the risk of frequent asthma symptoms. Those in poverty appeared to be more strongly affected by heavy traffic near their residences.

    View details for DOI 10.1016/j.annepidem.2008.01.006

    View details for Web of Science ID 000255530900001

    View details for PubMedID 18433665

  • Traffic and outdoor air pollution levels near residences and poorly controlled asthma in adults ANNALS OF ALLERGY ASTHMA & IMMUNOLOGY Meng, Y., Wilhelm, M., Rull, R. P., English, P., Ritz, B. 2007; 98 (5): 455-463

    Abstract

    Air pollution may exacerbate asthma.To investigate associations between traffic and outdoor air pollution levels near residences and poorly controlled asthma among adults diagnosed as having asthma in Los Angeles and San Diego counties, California.We estimated traffic density within 500 ft of 2001 California Health Interview Survey respondents' reported residential cross-street intersections. Additionally, we assigned annual average concentrations of ozone, nitrogen dioxide, particulate matter 2.5 and 10 micrometers or less in diameter, and carbon monoxide measured at government monitoring stations within a 5-mile radius of the reported residential cross-street intersections.We observed a 2-fold increase in poorly controlled asthma (odds ratio [OR], 2.11; 95% confidence interval [CI], 1.38-3.23) among asthmatic adults in the highest quintile of traffic density after adjusting for age, sex, race, and poverty. Similar increases were seen for nonelderly adults, men, and women, although associations seemed strongest in elderly adults (OR, 3.00; 95% CI, 1.13-7.91). Ozone exposures were associated with poorly controlled asthma among elderly adults (OR, 1.70; 95% CI, 0.91-3.18 per 1 pphm) and men (OR, 1.76; 95% CI, 1.05-2.94 per 1 pphm), whereas particulate matter 10 micrometers or less seemed to affect primarily women (OR, 2.06; 95% CI, 1.17-3.61), even at levels below the national air quality standard.Heavy traffic and high air pollution levels near residences are associated with poorly controlled asthma.

    View details for Web of Science ID 000246651200007

    View details for PubMedID 17521030

  • Living near heavy traffic increases asthma severity. Policy brief (UCLA Center for Health Policy Research) Meng, Y., Rull, R. P., Wilhelm, M., Ritz, B., English, P., Yu, H., Nathan, S., Kuruvilla, M., Brown, E. R. 2006: 1-5

    View details for PubMedID 16958190

  • Neural tube defects and maternal residential proximity to agricultural pesticide applications AMERICAN JOURNAL OF EPIDEMIOLOGY Rull, R. P., Ritz, B., Shaw, G. M. 2006; 163 (8): 743-753

    Abstract

    Residential proximity to applications of agricultural pesticides may be an important source of exposure to agents that have been classified as developmental toxins. Data on two case-control study populations of infants with neural tube defects (NTDs) and nonmalformed controls delivered in California between 1987 and 1991 were pooled to investigate whether maternal residential proximity to applications of specific pesticides or physicochemical groups of pesticides during early gestation increases the risk of these malformations. Maternal residential proximity within 1,000 m of pesticide applications was ascertained by linking mothers' addresses with agricultural pesticide use reports and crop maps. Odds ratios were computed by using conventional single- and multiple-pesticide and hierarchical multiple-pesticide logistic regression. In single-pesticide models, several pesticides were associated with NTDs after adjustment for study population, maternal ethnicity, educational level, cigarette smoking, and vitamin use. In a hierarchical multiple-pesticide model, effect estimates for only benomyl and methomyl suggested a possible association. Elevated risks of NTDs and anencephaly or spina bifida subtypes were also associated with exposures to chemicals classified as amide, benzimidazole, methyl carbamate, or organophosphorus pesticides and with increasing numbers of pesticides. These results suggest that ambient exposure to certain categories of agricultural pesticides may increase the risk of NTDs.

    View details for DOI 10.1093/aje/kwj101

    View details for Web of Science ID 000236612700008

    View details for PubMedID 16495467

  • Validation of self-reported proximity to agricultural crops in a case-control study of neural tube defects JOURNAL OF EXPOSURE SCIENCE AND ENVIRONMENTAL EPIDEMIOLOGY Rull, R. P., Ritz, B., Shaw, G. M. 2006; 16 (2): 147-155

    Abstract

    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.

    View details for DOI 10.1038/sj.jea.7500444

    View details for Web of Science ID 000235890600006

    View details for PubMedID 16047039

  • Historical pesticide exposure in California using pesticide use reports and land-use surveys: An assessment of misclassification error and bias ENVIRONMENTAL HEALTH PERSPECTIVES Rull, R. A., Ritz, B. 2003; 111 (13): 1582-1589

    Abstract

    We used California's Pesticide Use Report (PUR) and land-use survey data to conduct a simulation study evaluating the potential consequences of misclassifying residential exposure from proximity to agricultural pesticide application in health effect studies. We developed a geographic model linking the PUR with crop location data from land-use surveys to assess the impact of exposure misclassification from simpler exposure models based solely on PUR or land-use data. We simulated the random selection of population controls recruited into a hypothetical case-control study within an agricultural region. Using residential parcel data, we derived annual exposure prevalences, sensitivity, and specificity for five pesticides and relied on the PUR plus land-use model as the "gold standard." Based on these estimates, we calculated the attenuation of prespecified true odds ratios (ORs), assuming nondifferential exposure misclassification. True ORs were severely attenuated a) when residential exposure status was based on a larger geographic area yielding higher sensitivity but low specificity for exposure, in contrast to relying on a smaller area and increasing specificity; b) for less frequently applied pesticides; and c) with increasing mobility of residents among the study population. Considerable effect estimate attenuation also occurred when we used residential distance to crops as a proxy for pesticide exposure. Finally, exposure classifications based on annual instead of seasonal summaries of PUR resulted in highly attenuated ORs, especially during seasons when applications of specific pesticides were unlikely to occur. These results underscore the importance of increasing the spatiotemporal resolution of pesticide exposure models to minimize misclassification.

    View details for Web of Science ID 000185940800022

    View details for PubMedID 14527836

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