On-the-Job Pesticide Exposure Increases Risk of COPD

Workplace exposure to pesticides was linked to a higher risk of chronic obstructive pulmonary disease (COPD), a large U.K. study found.

Risk of COPD increased among adults ages 40-74 ever exposed to pesticides on the job (prevalence ratio [PR] 1.13, 95% CI 1.01-1.28), reported Sara De Matteis, MD, PhD, MPH, of Imperial College London, and colleagues.

Risk was increased even among individuals without asthma (PR 1.26, 95% CI 1.00-1.60) and those who have never smoked (PR 1.39, 95% CI 1.04-1.86), they noted in Thorax.

Cumulative exposure to pesticides greater than 10 exposure-unit years was also associated with heightened risk of COPD among all subjects (PR 1.32, 95% CI 1.12-1.56), with positive exposure-response trends (P=0.004), which were confirmed among never-smokers (P=0.005) and never-asthmatics (P=0.001).

"Occupational exposures are important, preventable causes of COPD," De Matteis and team wrote, noting that approximately 14% of COPD cases are related to workplace exposures.

A 2019 study also led by De Matteis identified agriculture, fishing, and groundskeeping, among others, as occupations linked to higher risk of COPD, and the researchers hypothesized that pesticides may be a common denominator.

In the U.S., approximately 15.7 million Americans have been diagnosed with COPD, according to the CDC. In 2020, chronic lower respiratory diseases including COPD were the sixth leading cause of death.

In the current study, the authors found no positive associations between "traditional 'dusty' exposures" and metal exposures and COPD risk, but previous investigations have linked "vapors, gases, dusts, and fumes," and "mineral dusts" with risk of COPD.

One potential explanation for the lack of a positive association with dust and metal exposures is that the jobs with significant exposure to these hazards, such as coal mining, were underrepresented in this voluntary study population, which was drawn from the U.K. Biobank, De Matteis and team explained.

For the study, over 300,000 U.K. Biobank participants with an email address were invited to complete an online job history timeline. Of the 116,000 who completed the form, 94,514 with acceptable spirometry and smoking data were included in the analysis (mean age 56, 56% women, 95% white). Over half of the study group were never-smokers, and only 5.6% were current smokers. About 11% of the study group had asthma.

COPD was defined as an FEV₁/FVC less than the lower limit of normal determined by spirometry. Overall in this study, the prevalence of spirometry-defined COPD was 8%. COPD was more common among current smokers (16.8%) compared with former smokers (8.6%) and never-smokers (6.9%).

To determine occupational exposures, De Matteis and colleagues used the ALOHA+ job exposure matrix, which assigns exposure levels of 10 hazard categories to different jobs. In this study, herbicides, insecticides, and fungicides were combined into one category of pesticides, since there was significant overlap between the subgroups and sparse data for each, "making it impossible to disentangle their specific effects," they wrote.

The authors noted that their study may be prone to selection bias on multiple levels -- the U.K. Biobank itself is a voluntary group that is disproportionately white, educated, non-smoking, and composed of women. They also had no data on people who declined the email invite.

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