Night shift work characteristics and occupational co-exposures in industrial plants in Łódź, Poland

Night shift work involving circadian rhythm disruption has been classified by IARC as a probably carcinogenic to humans (Group 2A). Little is known about co-exposures of the night shift work in occupational settings. The aim of our study was to characterize night shift work systems and industrial exposures occurring in the manufacturing plants in Łódź, Poland, where night shift work system operates, with particular focus on potential carcinogens.

Data on the night shift work systems and hazardous agents were collected through survey performed in 44 enterprises. The identified hazardous agents were checked using the IARC carcinogen list, and the harmonized EU classification of chemical substances. We also examined databases of the Central Register of Data on exposure to substances, preparations, agents and technological processes showing carcinogenic or mutagenic properties in Poland.

The most common system of work among studied enterprises employed 3 (8-hour) shifts within a 5-day cycle. We identified as many as 153 hazards occurring in the environment of the plants, with noise, carbon monoxide and formaldehyde recorded as the most common ones. Out of these hazards, 11 agents have been classified by IARC to group 1 - carcinogenic to humans, whereas 10 agents have been classified as carcinogens by the regulation of European Classification of carcinogens. Analysis of the data from the Central Register revealed that 6 plants reported presence of carcinogens in the environment of work.

In our study we observed that in none of the workplaces the night shift work was a single exposure. Further epidemiological studies focusing on investigation of health effects of the night shift work should identify occupational co-exposures and examine them as potential confounders.