Methods: Outdoor security non-smoking guards (N = 12) wore TSI DustTrack AM520 aerosol monitors with a 10-μm impactor for 8 hours of outdoor shift. Ten samples (k = 10) from each worker were obtained for the cold season (November-March) from various locations across Almaty. Total sampling time was 57600 minutes. We compared normalized time-weighted average (TWA) concentrations for 8-hour shifts within and between workers using analysis of variance (ANOVA) and assessed compliance with environmental exposure limit (EEL) (0.060 mg/m3) via exceedance (γ) and probability of overexposure (θ).
Results: PM10 TWA ranged from 0.050 to 2.075 mg/m3 with the geometric mean 0.366 and median 0.352 mg/m3. PM10 TWA distribution was left-skewed with large variation. The fold-range of within-person variability, containing 95% of the exposure concentration (wR0.95) was 13, whereas between-person fold-range (bR0.95) was 3. However, between-person variance exceeded the one within with F-ratio 2.797 (p = 0.003) with statistical power 97% at α = 0.05. Only two of 120 samples had TWA below EEL, yielding γ = 0.995 and θ = 1.
Conclusions: Outdoor workers in polluted cities like Almaty are exposed to very high levels of PM10 during the cold season. Urgent action should be taken to regulate such occupational exposure and to raise awareness of workers and employers on hazards associated with it.