Exposure to fumigants and residual chemicals in workers handling cargo from shipping containers and export logs : a study of exposure determinants and neuropsychological symptoms : a thesis by publications presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Public Health (Epidemiology) at Massey University, Wellington, New Zealand

Abstract

Fumigants are widely used in shipping containers and on export logs for biosecurity reasons. This thesis aimed to: (i) assess concentrations of fumigants and off-gassed chemicals in closed containers; (ii) identify container characteristics associated with high concentrations; (iii) assess personal exposure levels of workers exposed to these chemicals; and (iv) assess whether exposed workers report more neuropsychological symptoms.

Air samples were collected from 490 sealed containers and at opening of 46 containers, and 193 personal full-shift air samples were collected for 133 container handlers, 15 retail workers, 40 workers loading export logs, and 5 fumigators. Samples were analysed by Selected Ion Flow Tube Mass Spectrometry for several common fumigants and harmful chemicals frequently found in shipping containers. Levels were compared to the New Zealand Work Exposure Standard (WES) and the Threshold Limit Value (TLV). A neuropsychological symptom questionnaire was completed by 274 container handlers, 38 retail workers, 35 fumigators, 18 log workers, and a reference group of 206 construction workers.

Fumigants were detected in 11.4% of sealed containers (ethylene oxide 4.7%; methyl bromide 3.5%). Chemicals other than fumigants were detected more frequently, particularly formaldehyde (84.7%). Some cargo types (e.g. rubber products) and countries of origin (e.g. China) were associated with higher chemical concentrations. Fumigants were detected in both fumigated and non-fumigated containers. Ambient chemical concentrations in closed and just opened containers regularly exceeded the NZ WES and TLV. Personal exposure measurements never exceeded the NZ WES, although for 26.2% of samples the TLV for formaldehyde was exceeded. Duration spent unloading containers was associated with higher levels of ethylene oxide, C2-alkylbenzenes and acetaldehyde.

Exposed workers were more likely to report ≥10 symptoms, and particularly for the fatigue domain. Longer cumulative duration of unloading containers was associated with more symptoms (Odds Ratio (OR) 7.5, 95% Confidence Interval (CI) 1.7-32.8), and specifically for symptoms in the memory/-concentration domain (OR 6.8, 95%CI 1.5-30.3), when comparing the highest exposure duration tertile to the lowest.

In conclusion, while workers’ full-shift exposure levels to container chemicals are lower than previously expected (based on the high levels measured in closed containers), they may nonetheless cause long-term health effects.