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Effects of high ambient temperatures on liver function in an occupational population: Examining the mediation role of inflammatory cells and moderation role of age factors

Journal of Exposure Science & Environmental Epidemiology (2026) Cite this article

Abstract

Background

Occupational exposure to high ambient temperature may affect liver function, but pathways remain unclear.

Objective

To examine associations between high ambient temperature and liver enzymes among steelworkers, and to evaluate mediation by inflammatory cells and moderation by age.

Methods

In this cross-sectional study of 1111 steelworkers, high ambient temperature exposure was classified at the workshop level using wet-bulb globe temperature (WBGT) per Chinese standards (GBZ 2.2-2007): time-weighted average WBGT ≥ 25 °C (high-temperature) vs. <25 °C (control). Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and inflammatory cell counts were measured from venous blood. Multivariable generalized linear models estimated associations; mediation (via lymphocytes) used bootstrap confidence intervals; age moderation was tested.

Results

Compared with controls, the high ambient temperature exposure group exhibited elevated levels of ALT and AST, as well as higher counts of white blood cells, lymphocytes, monocytes, and eosinophils (P < 0.05). High ambient temperature exposure emerged as independently associated with ALT (β = 0.384, 95%CI: 0.222, 0.546) and AST (β = 0.238, 95%CI:0.065, 0.410) levels. Lymphocyte counts statistically mediated the relationship between high ambient temperature exposure and elevated serum ALT (β = 0.062, 95%CI: 0.026, 0.104) and AST (β = 0.046, 95%CI:0.009, 0.092) levels. Additionally, age only moderated the path between high ambient temperature exposure and lymphocyte count (β = -0.192, 95%CI: -0.316, -0.067).

Significance

Occupational heat was associated with higher ALT/AST; lymphocyte-related indirect association was observed and attenuated with age. Longitudinal and mechanistic studies are needed to assess causality.

Impact

Findings support WBGT-based heat monitoring, routine ALT and AST screening in hot posts, and targeted acclimatization hydration and work- rest protocols, especially for younger workers, while future studies test whether enhanced heat controls improve liver outcomes.

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Fig. 1: Serum ALT and AST levels in the exposure group and control group across demographic and lifestyle subgroups.
The alternative text for this image may have been generated using AI.
Fig. 2: Correlation among high ambient temperature exposure, liver function index and inflammatory cells.
The alternative text for this image may have been generated using AI.
Fig. 3: Mediating effect model of high ambient temperature exposure on ALT levels.
The alternative text for this image may have been generated using AI.
Fig. 4: Mediating effect model of high ambient temperature exposure on AST levels.
The alternative text for this image may have been generated using AI.
Fig. 5: Moderated mediation model of the association between high ambient temperature and ALT levels.
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Fig. 6: Interaction of age and high ambient temperature exposure on lymphocyte count.
The alternative text for this image may have been generated using AI.

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Data availability

Data will be made available upon request.

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Acknowledgements

The authors extend their gratitude to all individuals who volunteered to participate in this study. This work was supported by the National Natural Science Foundation of China (NSFC81872597, 81001239).

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Authors and Affiliations

  1. Department of Urology, Peking University Third Hospital, Peking University, Beijing, China

    Mengqing Yan

  2. Center for Reproductive Medicine, Department of Obstetrics and Gynecology, Peking University Third Hospital, Peking University, Beijing, China

    Mengqing Yan

  3. Department of Occupational and Environmental Health, College of Public Health, Zhengzhou University, Zhengzhou, China

    Mengqing Yan, Bin Yang, Menghan Li & Wei Wang

  4. Department of Public Health The First People’s Hospital of Yunnan Province School of Medicine, Kunming University of Science and Technology, Kunming, 650032, China

    Bin Yang

  5. Zhuji People’s Hospital of Zhejiang Province, Shaoxing, China

    Wenjun Kang

  6. Department of Epidemiology and Biostatistics, College of Public Health, Zhengzhou University, Zhengzhou, China

    Yongli Yang

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  6. Wei Wang
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Contributions

Wei Wang and Mengqing Yan conceived of the study. Mengqing Yan and Bin Yang designed the study. Mengqing Yan wrote the main manuscript text. Bin Yang, Menghan LI, Wenjun Kang and Yongli Yang collected the data and did the data analysis. All authors read and revised the manuscript and gave final approval for publication.

Corresponding author

Correspondence to Wei Wang.

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Competing interests

The authors declare no competing interests.

Ethics approval and consent to participate

The study was approved by ethical approval from Zhengzhou University’s ethics committee (ZZUIRB2021-153). Informed consent was obtained from all participants prior to study participation. This study was conducted in accordance with the principles of the Declaration of Helsinki.

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Yan, M., Yang, B., Li, M. et al. Effects of high ambient temperatures on liver function in an occupational population: Examining the mediation role of inflammatory cells and moderation role of age factors. J Expo Sci Environ Epidemiol (2026). https://doi.org/10.1038/s41370-026-00853-y

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