Introduction While exposure-response relationships for work-related asthma have been studied in wood processing workers, few studies have used multiple exposure indices to evaluate various clinical endpoints.

Objectives To investigate exposure-response relationships for work-related respiratory symptoms, airway obstruction, bronchial hyperresponsiveness, and exhaled nitric oxide (FeNO) among Mozambiquan wood processing workers.

Methods A cross-sectional study of 450 workers using inhalable wood dust particulate concentrations assigned to workers based on personal environmental exposure samples (n=124) collected for different jobs. Exposure metrics of current and cumulative dust exposure were modeled using multivariate linear and logistic regression for the clinical endpoints, adjusted for confounders (age, gender, atopy, smoking).

Results The mean inhalable dust concentrations modelled were 3.29 mg/m3 (GSD: 3.04), cumulative exposure in current job was 26.23 mg/m3-yr (GSD: 2.94) and cumulative exposure over all jobs was 24.07 mg/m3-yr (GSD: 2.94). The mean age of predominately male workers was 38 years, among whom 76% were non-smokers and 50% atopic. Work-related ocular-nasal symptoms were associated, in a dose-dependent manner, with exposure groups (EGs) categorized according to current dust particulate levels (medium, 4.68–4.71 mg/m3: OR = 3.45, 95% CI: 1.21 – 10.63; high, >4.71 mg/m3: OR = 3.66, 95% CI: 1.19 – 11.26) versus low EG ( < 4 .68 mg/m3) in adjusted models. Work-related asthma symptoms were associated with mean cumulative exposure (OR = 1.01, 95% CI: 1.00 – 1.02) in adjusted models. FeNO was associated with cumulative exposure in current job (quartile 2, OR= 1.23, 95% CI: 1.02 – 1.51; quartile 4, OR= 1.23, 95% CI: 1.02 – 1.49) as well cumulative exposure across all jobs in the factory (quartile 4, OR= 1.22, 95% CI: 1.01 – 1.48) versus quartile 1 in adjusted models.

Conclusion This study demonstrated positive exposure-response relationships between wood dust particulate for both work-related ocular-nasal symptoms as well as asthma, suggestive of an acute irritant.