Background Small airways obstruction (SAO) is a key feature of both Chronic Obstructive Pulmonary Disease and asthma, which have been associated with workplace exposures. Whether SAO, which may occur early in the development of obstructive lung disease and without symptoms, also associates with occupational exposures is unknown.

Methods Using UK Biobank data, we derived measurements of SAO from the 65,145 participants with high quality spirometry and lifetime occupational histories. The ALOHA+ Job Exposure Matrix was used to assign lifetime occupational exposures to each participant. The association between SAO and lifetime occupational exposures was evaluated using a logistic regression model adjusted for potential confounders. A second logistic regression model was run to also account for potential co-exposures.

Results SAO was present in varying proportions of the population depending on definition used: 5.6% (FEF25–75<LLN)and 21.4% (FEV3/FEV6<LLN). After adjustment for confounders and co-exposures, people in the highest category of exposure to pesticides were significantly more likely to have SAO (FEV3/FEV6<LLN: OR 1.24, 95%CI 1.06–1.44). The association between pesticides and SAO showed an exposure-response pattern. SAO was also less likely among people in the highest exposure categories of aromatic solvents (FEV3/FEV6<LLN: OR 0.85, 95%CI 0.73–0.99) and metals (FEV3/FEV6<LLN: OR 0.77, 95%CI 0.62–0.94).

Conclusion Our findings suggest that occupational exposure to pesticides play a role in the SAO. However, further work is needed to determine causality, and identify the specific component(s) responsible and the underlying mechanisms involved.