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Objectives: With continued global warming, the effects of elevated temperatures on the health of agricultural workers are a particular concern. This study characterized the levels of heat stress in Thai sugarcane workers and investigated whether season and harvesting method were associated with it., Methods: Three hundred sugarcane workers in Nakhon Sawan Province, Thailand, were recruited, and information on demographics, working conditions, and clothing characteristics was collected from participants during the cooler months (n = 152 participants, mid-January to mid-February) and hotter month (n = 148, March). Heat stress was measured using the Wet Bulb Globe Temperature (WBGT) index, and the WBGT instruments were operated for a full work shift in the sugarcane fields where the participants worked. One-hour time weighted average (TWA) effective WBGT (WBGTeff-1hrTWA) estimates were determined for different times of the day based on the measured WBGT and clothing adjustment factor., Results: The average WBGTeff-1hrTWA in the cooler months ranged from 22.5 °C during the early morning to 31.3 °C during the hottest time of the day, and for the hotter month, it ranged from 25.4 °C to 33.9 °C, respectively. The measured WBGT, natural wet-bulb temperature (Tnwb), dry-bulb temperature (Tdb), globe temperature (Tg), air velocity (Av), and absolute water vapor pressure (ea) were all statistically significantly higher in the hotter month than in the cooler months. Harvesting during the hotter month and harvesting burnt sugarcane were significantly associated with increased effective WBGT. The harvesters' heat stress in both seasons exceeded the American Conference of Governmental Industrial Hygienists - Threshold limit value for 72.7% of the working time in the cooler months and 90.9% in the hotter month., Conclusions: The heat stress in Thai sugarcane workers was high in both seasons, particularly in the hotter month and when harvesting burnt sugarcane. This results in a very high risk of developing heat-related health effects, and measures are needed to reduce heat stress. Heat stress in agricultural and other outdoor work in tropical climates is an immediate and growing problem., (© The Author(s) 2025. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.)

Exploitation of offshore oil reserves, heightened traffic in marine transportation routes, and the release of petrochemicals from the thawing of permafrost and glaciers is increasing the bioavailability of polycyclic aromatic hydrocarbons (PAHs) to aquatic organisms. This availability may also change with the seasons as temperature changes accessibility of Arctic transport routes and the degree of land- and ice-melt and thus run-off into coastal ecosystems. Seasonal temperature change also remodels the ion channels in the heart of fish to facilitated preserved cardiac function across a range of temperatures. How this seasonal cardiac remodelling impacts vulnerability to pollutants is currently unknown. In this study we accessed the electrical activity of navaga cod (Eleginus nawaga) ventricular cardiomyocytes under the dual influence of seasonal change and varying concentrations of a pervasive PAH pollutant, 3-methylphenanthrene (3-MP). We used whole-cell patch-clamp to elucidate the effect of various doses of 3-MP on action potential (AP) parameters and the main ion currents (I Kr , I K1 , I Na , I Ca ) in ventricular cardiomyocytes isolated from navaga cod in winter and summer at the White Sea, close to the Russian Arctic circle. Navaga cod ventricular cardiomyocytes were particularly vulnerable to 3-MP during the winter season. Exposure to 300 nM 3-MP resulted in significant changes in AP duration in winter-acclimatized fish, whereas no such changes were observed in summer-acclimatized fish. The I Kr current was the most sensitive to 3-MP, with a winter IC 50 of 49.7 nM and a summer IC 50 of 53 μM. The I Na current also exhibited seasonal shifts in sensitivity to 3-MP, with IC 50 values of 2.39 μM in winter-acclimatized fish and 7.73 μM in summer-acclimatized fish. No significant differences were observed in the effect of 3-MP on the peak I Ca current, although 3 μM of 3-MP caused a pronounced decrease in charge transferred by I Ca (e.g. Q Ca ) in both seasons. The I K1 current was insensitive to 3-MP in both winter and summer fish. These findings highlight how remodelling of the fish heart with changing season alters the potency of PAH pollution. This paper lays the groundwork for future research on the molecular mechanisms that drive the altered seasonal potency of pollutants in navaga cod and other species., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)