Farm work is a known risk factor for occupational exposure to pollutants linked to obstructive airway diseases like COPD, but a new report from the CDC finds an elevated risk of exposure in rural workers with no connection to the agricultural industry.
When researchers from the National Institute for Occupational Safety and Health (NIOSH) compared exposures to vapor-gas, dust, and fumes (VGDF) by occupation in a cohort of adult workers in rural Iowa to adult workers in six urban areas across the U.S., they were not surprised to find the highest exposures among farm workers and former farmers.
But they were surprised that exposures among rural workers who had never farmed were almost twice as high as those seen in urban workers.
Findings from the NIOSH report were published online Thursday in the CDC's Morbidity and Mortality Weekly Report.
"Around 15% of urban workers had medium-to-high exposures to vapor-gas, dust, and fumes, compared to 27% of the rural never-farmers," Paul Henneberger, ScD, of NIOSH's lab in Morgantown, West Virginia, told MedPage Today.
Smoking is the biggest risk factor for COPD, by far, but the American Thoracic Society estimates that 15% of COPD cases in the general population are attributed to occupational exposures.
Occupational exposures to pollutants from vapor-gas, dust and fumes have specifically been linked to COPD in several studies.
Henneberger noted that while VGDF exposures in agricultural occupational settings has been well studied, little has been known about exposures among rural workers not involved in farm work.
The researchers evaluated data from a baseline questionnaire completed by adult rural residents of Iowa participating in the Keokuk County Rural Health Study (KCRHS). Job distribution and occupational exposures to VGDF was analyzed and stratified by farming status (current, former, and never) and compared with a cohort of urban workers participating in the Multi-Ethnic Study of Atherosclerosis (MESA).
Occupational exposure at the respondents' most recent job was assessed with a job-exposure matrix developed for COPD (COPD JEM), which rated VGDF exposure levels as non or low, medium, and high.
Among the main findings:
- The 1,699 KCRHS (rural) participants were almost three times more likely to have medium or high occupational VGDF exposure (43.2%) at their last job than their urban MESA counterparts (15.0% of 3,667 participants)
- One-in-five (20.8%) rural participants currently farmed, 43.1% were former farmers, and approximately one third (36.1%) had never farmed
- These three farming groups differed in VGDF exposure at the last job, with the prevalence of medium or high exposure at 80.2% for current farmers, 38.7% for former farmers, and 27.4% for never farmers
- 15% of urban workers had medium or high level of VGDF exposure
Rural workers who did not work in the farming industry were more likely to have blue collar jobs than urban workers, while urban workers were more likely to be categorized as management/professional.
And while current and former farmers made up around 64% of the rural cohort, they accounted for 88% of rural participants with high total VGDF exposures in their most recent jobs.
"Any findings of an association between respiratory health and high VGDF exposure might be primarily result of farming exposures, and determining whether an exposure-response relation is evident both for those with and those without farming experience is important," the MMWR report stated.