埃が地下鉄職員に与える影響を探る最大規模の研究(Largest study explores impact of dust on Tube staff)

2024-03-14

2024-03-13 インペリアル・カレッジ・ロンドン(ICL)

ロンドン帝国大学の研究では、微粒子(PM2.5)の濃度が高い地域で働く職員は、病欠の回数が多い傾向があることがわかった。ただし、これがPM2.5に直接的に病欠を引き起こす証拠とは言えず、さらなる研究が必要とされる。一部の職員はPM2.5濃度が高い地域で病欠が多い傾向があるが、これらの関連は明確ではない。研究チームは、地下鉄システムでの健康効果と大気の関連性を調査した最大かつ包括的な研究であり、世界中の地下鉄ネットワークに影響を与える可能性がある。

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ロンドン地下鉄における粒子状物質への職業曝露と職員の病気欠勤 Occupational exposure to particulate matter and staff sickness absence on the London underground

Justie Mak, Johanna Feary, André F.S. Amaral, Emma Marczylo, Paul Cullinan, David C. Green
Environment International Available online:27 February 2024
DOI:https://doi.org/10.1016/j.envint.2024.108529

Highlights

•Largest occupational cohort study conducted in a subway system.

•PM_2.5 mass concentration on the London Underground can be 15 times higher than outdoor air in London.

•Subway PM exposure amongst staff is heterogenous and drivers have the highest exposures.

•Office staff had lower sickness absence rates from all-causes and infections.

•No exposure response relationship between PM_2.5 and sickness absence was seen to support causal associations.

Abstract

The London Underground (LU) employs over 19,000 staff, some of whom are exposed to elevated concentrations of particulate matter (PM) within the network. This study quantified the occupational exposure of LU staff to subway PM and investigated the possible association with sickness absence (SA).

A job exposure matrix to quantify subway PM_2.5 staff exposure was developed by undertaking measurement campaigns across the LU network. The association between exposure and SA was evaluated using zero-inflated mixed-effects negative binomial models.

Staff PM_2.5 exposure varied by job grade and tasks undertaken. Drivers had the highest exposure over a work shift (mean: 261 µg/m³), but concentrations varied significantly by LU line and time the train spent subway.

Office staff work in office buildings separate to the LU network and are unexposed to occupational subway PM_2.5. They were found to have lower rates of all-cause and respiratory infection SA compared to non-office staff, those who work across the LU network and are occupational exposed to subway PM_2.5. Train drivers on five out of eight lines showed higher rates of all-cause SA, but no dose–response relationship was seen. Only drivers from one line showed higher rates of SAs from respiratory infections (incidence rate ratio: 1.24, 95% confidence interval 1.10–1.39). Lower-grade customer service (CS) staff showed higher rates of all-cause and respiratory infection SA compared to higher grade CS staff. Doctor-certified chronic respiratory and cardiovascular SAs were associated with occupational PM_2.5 exposure in CS staff and drivers.

While some groups with higher occupational exposure to subway PM reported higher rates of SA, no evidence suggests that subway PM is the main contributing factor to SA. This is the largest subway study on health effects of occupational PM_2.5 exposure and may have wider implications for subway workers, contributing to safer working environments.