Maria T. Stoecklin-Marois

Engaging a Hard-to-Reach Population in Research: Sampling and Recruitment of Hired Farm Workers in the MICASA Study

Hired farm workers provide the majority of the workforce for Californias labor-intensive agricultural sector Agriculture is one of the most hazardous occupations, but there has been little research into the etiology of poor health outcomes that occur disproportionately in hired farm worker populations. MICASA is a cohort investigation of occupational and environmental health risks in hired farm worker households in Mendota, California, that employed a two-stage sampling process, including random selection of census blocks and door-to-door enumeration. The aim of this analysis was to evaluate the success of the sampling process and compare demographics of the enumerated population to other regional samples of Latino populations. In the enumeration, 1257 addresses were mapped and 729 hired farm worker households were enumerated. Findings showed no significant differences between the enumerated population and the resulting MICASA study sample; however, the MICASA population was more likely to be male, from Central America, work in agriculture, and have fewer years residency in the U.S. than California Health Interview Survey (CHIS) respondents. Additionally, 9.4% of the enumerated dwellings were back houses or unofficial dwellings and may have been missed by the U.S. Census 2000. Demographic comparisons between the enumerated population, census data, and CHIS data highlight the differences in these sampling methods and suggest possible demographic changes in hired farm workers in California. While difficulties in accessing hired farm workers often account for the lack of population-based research, the MICASA cohort provides an opportunity to examine occupational health patterns relevant to other farm worker populations.

Pyrethroids in house dust from the homes of farm worker families in the MICASA study.

Indoor pesticide exposure is a growing concern, particularly for pyrethroids, a commonly used class of pesticides. Pyrethroid concentrations may be especially high in homes of immigrant farm worker families, who often live in close proximity to agricultural fields and are faced with poor housing conditions, potentially causing high pest infestation and pesticide use. We investigate levels of pyrethroids in the house dust of farm worker family homes in a study of mothers and children living in Mendota, CA, within the population-based Mexican Immigration to California: Agricultural Safety and Acculturation (MICASA) Study. We present pesticide use data and levels of pyrethroid pesticides in indoor dust collected in 2009 as measured by questionnaires and a GC/MS analysis of the pyrethroids cis- and trans-permethrin, cypermethrin, deltamethrin, esfenvalerate and resmethrin in single dust samples collected from 55 households. Cis- and trans-permethrin had the highest detection frequencies at 67%, with median concentrations of 244 and 172ng/g dust, respectively. Cypermethrin was detected in 52% of the homes and had a median concentration of 186ng/g dust. Esfenvalerate, resmethrin and deltamethrin were detected in less than half the samples. We compared the pyrethroid concentrations found in our study to other studies looking at both rural and urban homes and daycares. Lower detection frequencies and/or lower median concentrations of cis- and trans-permethrin and cypermethrin were observed in our study as compared to those studies. However, deltamethrin, esfenvalerate and resmethrin were detected more frequently in the house dust from our study than in the other studies. Because households whose children had higher urinary pyrethroid metabolite levels were more likely to be analyzed in this study, a positive bias in our estimates of household pyrethroid levels may be expected. A positive association was observed with reported outdoor pesticide use and cypermethrin levels found in the indoor dust samples (rs=0.28, p=0.0450). There was also a positive association seen with summed pyrethroid levels in house dust and the results of a pesticide inventory conducted by field staff (rs=0.32, p=0.018), a potentially useful predictor of pesticide exposure in farm worker family homes. Further research is warranted to fully investigate the utility of such a measure.

Agricultural work and chronic musculoskeletal pain among Latino farm workers: the MICASA study.

BACKGROUND Agriculture poses varied dangers to hired farm workers in the U.S., but little information exists on occupational risks for chronic musculoskeletal pain. We examined common work positions, such as kneeling, carrying heavy loads, and repetitive motion that may increase the risk for chronic musculoskeletal pain. METHODS MICASA is a population-based study of occupational exposures and health in hired farm workers in California. This analysis includes 759 participants, 18-55 years old, engaged in farm work and residing in Mendota, CA. Chronic pain was defined as pain lasting 6 weeks or longer at specific body sites (back, knee, hip, etc.) over the entire farm work career. RESULTS Mean age was 37.9 years. Sixty-five percent participants were born in Mexico, 27.7% were born in El Salvador, and 4.2% were U.S-born. Chronic pain was associated with older age and female sex. After adjustment for age, years working in agriculture, and smoking, stooping/bending >30 hr/week among both men (OR = 2.49, 95% CI: 1.03-5.99) and women (OR = 2.15, 95% CI: 1.04-4.46) was associated with chronic hip pain. Driving tractors or other heavy farm equipment >60 hr/week was associated with increased odds of chronic hip pain (OR = 2.16, 95% CI: 1.02-4.54) among men. We also observed significant associations with kneeling or crawling >35 hr/week among women for both chronic back pain (OR = 2.96, 95% CI: 1.27-6.93) and knee pain (OR = 3.02, 95% CI: 1.07-8.50), respectively. CONCLUSIONS Chronic musculoskeletal pain is prevalent among farm workers and is associated with common work positions. Further research should focus on developing preventive interventions for tasks associated with increased pain risk. These interventions should be targeted to specific types of agricultural tasks.

Concentrations of the urinary pyrethroid metabolite 3-phenoxybenzoic acid in farm worker families in the MICASA study

Indoor pesticide exposure is a growing concern, particularly from pyrethroids, a commonly used class of pesticides. Pyrethroid concentrations may be especially high in homes of immigrant farm worker families who often live in close proximity to agricultural fields, and are faced with poor housing conditions, causing higher pest infestation and more pesticide use. We investigate exposure of farm worker families to pyrethroids in a study of mothers and children living in Mendota, CA within the population-based Mexican Immigration to California: Agricultural Safety and Acculturation (MICASA) Study. We present pyrethroid exposure based on an ELISA analysis of urinary metabolite 3-phenoxybenzoic acid (3PBA) levels among 105 women and 103 children. The median urinary 3PBA levels (children=2.56 ug/g creatinine, mothers=1.46 ug/g creatinine) were higher than those reported in population based studies for the United States general population, but similar to or lower than studies with known high levels of pyrethroid exposure. A positive association was evident between poor housing conditions and the urinary metabolite levels, showing that poor housing conditions are a contributing factor to the higher levels of 3PBA seen in the urine of these farm worker families. Further research is warranted to fully investigate sources of exposure.

Occupational Exposures and Migration Factors Associated With Respiratory Health in California Latino Farm Workers: The MICASA Study

Objective:To evaluate associations of agricultural work and migration on self-reported respiratory symptoms in a Latino farm worker sample. Methods:Work history and respiratory symptoms were assessed in 702 workers through interviews in a community-based cohort. Results:Prevalence was 6% for asthma, 5% for chronic cough, 3% for chronic bronchitis, and 7% for persistent wheeze. The total number of years in agriculture was associated with asthma; however, time-weighted average dust exposure, use of protective equipment, and pesticide use in the past 12 months were not associated with respiratory outcomes. Living 15 years or more in the United States (adjusted odds ratio = 3.60; 95% confidence interval = 1.16 to 11.16) and medium/high acculturation (adjusted odds ratio = 6.06; 95% confidence interval = 1.40 to 26.29) were associated with increased odds of asthma in women. Conclusions:Analysis of this community-based Latino farm worker cohort identified associations with asthma, particularly with migration factors in women.

Adherence to Dietary Recommendations Is Associated with Acculturation among Latino Farm Workers

We examined adherence to dietary recommendations on fruit/vegetable and fat intake and identified correlates with acculturation indicators as well as with family, lifestyle, and occupational factors in a farm worker cohort in central California. Interviewer-administered questionnaires for this cross-sectional study were completed from January 2006 to April 2007. Participants were 18- to 55-y-old Latinos living in Mendota in a farm worker household. We assessed fruit/vegetable consumption and fat intake using the Block Fruit/Vegetable/Fiber Screener and the Block Dietary Fat Screener, respectively. Survey data analysis methods for contingency tables and logistic regression were used for assessing associations. The sample included 802 participants, reporting mean fruit and vegetable intake ( ± SD) of 5.0 ± 1.5 daily servings, and 47% reporting < 5 daily servings. Being born in Mexico or Central America and longer United States residency were associated with higher odds of consuming ≥ 5 daily fruit/vegetable servings and more frequent consumption of field products while working was associated with lower adherence to this recommendation. The average daily percent of calories from fat was 35.0 ± 4.1% and 53% of participants consumed > 35% of daily calories from fat. Men born in Mexico, women born in Central America, and participants who worked in fruit or vegetable crops had higher odds of consuming ≤ 35% of calories from fat. Higher acculturation level, United States school attendance, and having a child at home were associated with lower adherence to this recommendation. Acculturation, family, and occupational correlates of diet quality were identified in this underserved, immigrant population. Our findings may assist program targeting and intervention efforts.

Agricultural Work Exposures and Pulmonary Function Among Hired Farm Workers in California (The MICASA Study)

ABSTRACT Despite California’s dependence on hired farm labor, scarce research has been conducted on the respiratory health of hired farm workers. Agricultural exposures to inorganic and organic dusts can adversely affect an individual’s respiratory health and differ by farm type and job task. The purpose of the present analysis was to examine associations between agricultural work exposures and pulmonary function among 450 California farm workers. Data were collected as part of the Mexican Immigration to California: Agricultural Safety and Acculturation (MICASA) study, a prospective cohort study examining occupational risk factors and health of hired farm worker families in Mendota, California. Time-weighted self-reported average (TWSRA) dust scores were calculated from assessments of past-12-month agricultural work history. Other dust exposure indicator variables included months worked in agriculture in the past 12 months and years worked in agriculture. Multiple linear regression modeled FEV1 (forced expiratory volume in 1 second), FEF25–75% (forced midexpiratory flow rate), FVC (forced vital capacity), FEV6, FEV1/FVC, and FEV1/FEV6 separately. Seventy-six percent of participants had worked in agriculture in the past year. In models conducted for crops and tasks separately, high TWSRA dust score was associated with better FEV6. Crop and task models showed associations between greater months worked in agriculture in the past year and better FEV1, FEF25–75%, and FEV6. Both models also found greater years worked in agriculture to be associated with worse FEV1/FEV6. Results were generally in the opposite direction as expected given past research but not uncommon. Future research should investigate relationships between pulmonary function and agricultural dust exposure over a lifetime and changes in pulmonary function over time.

Acculturation-Related Predictors of Very Light Smoking Among Latinos in California and Nationwide

The prevalence of light smoking has increased among Latinos. The purpose of this study was to identify demographic and acculturation-related factors associated with very light smoking, defined as smoking 1–5 cigarettes per day (CPD), among Latinos in California and nationwide. Latino smokers in the 2007–2008 National Health and Nutrition Examination Survey (NHANES) or the 2009 California Health Interview Survey (CHIS) were analyzed. Logistic regression assessed factors associated with very light smoking. Among NHANES smokers, those born in Mexico or who lived fewer years in the US were more likely to be very light smokers than 6+ CPD smokers. Among CHIS smokers, those born in Mexico, in another Spanish speaking country, or who spent smaller percentages of their life in the US were more likely to be very light smokers. Findings from this study can be used to design tobacco control media campaigns that include very light smokers.

Agricultural Injury in California Hispanic Farm Workers: MICASA Follow-up Survey

ABSTRACT The authors report here results from the first follow-up survey of the Mexican Immigration to California: Agricultural Safety and Acculturation (MICASA) cohort of community-dwelling immigrant Hispanic farm workers in Californias Central Valley. Among 560 participants the authors observed cumulative 1-year injury incidence of 6.6% (all injuries) and 4.3% (agricultural injuries). Increased prospective injury risk was associated with males, US birth, years lived in the United States, family income, and poor self-rated health. Agricultural injuries were associated most frequently with being struck by an object, falls, and cutting instruments, whereas over two thirds of nonagricultural injuries involved motor vehicles. Prevention should focus on safe handling of tools and materials, falls, and motor vehicle safety.

Cohort study of physical activity and injury among Latino farm workers

INTRODUCTION This study characterized physical activity and its association with injury among Latino farm workers. METHODS An interviewer-administered questionnaire was used to collect baseline and follow-up data on 843 and 640 Latino farm workers, respectively. Participants were 18-55 years old, engaged in farm work and residing in Mendota, CA at baseline interview. The questionnaire assessed self-reported physical activity and risk of injury. RESULTS The 12 month prevalence of injury decreased from 9.0% at baseline to 6.9% at follow up interview. In GEE models adjusted for age, follow-up time, gender, smoking, income and years working in agriculture, poor/fair self-assessed health status (OR = 1.82, 95% CI: 1.18-2.82) and 2-3 hr per day of sitting/watching TV/using a computer (OR = 0.50, 95% CI: 0.30-0.83) were significantly associated with injury. CONCLUSIONS Physical activity was not associated with injury in this population. Efforts to reduce injuries should focus on known risk factors such as poor health status.