Climate crisis: effects of extreme temperatures on the health of the working population

The annual joint meeting of the Spanish Society of Epidemiology (SEE) and the Portuguese Society of Epidemiology (APE) was held in Porto on the 7th of September. During this meeting, several researchers from the Barcelona Biomedical Research Park (PRBB) participated in a round table sponsored by the SEE’s Occupational Health working group. The central theme of the discussion revolved around the impact of extreme temperatures and thermal discomfort on workers’ health.

This article, written by the round table participants, summarises the main studies and conclusions discussed at the meeting.

The impacts of the climate crisis on people’s health are becoming increasingly apparent. In its report last March, the Intergovernmental Panel on Climate Change (IPCC) once again warned of the catastrophic consequences of the climate crisis on global health. In Spain, the effects of the climate crisis are clearly visible, with rising temperatures, increasingly frequent heat waves, a decrease in rainfall and a greater frequency and intensity of extreme weather events.

In the workplace, the effects of climate change on health can be particularly relevant. Those who work outdoors and are exposed to extreme weather conditions, whether intense heat or cold, as well as air pollution, or those who work in unheated or poorly ventilated indoor spaces, are at increased risk of climate-related diseases and health problems. This emerging challenge is of great public health relevance. Within these effects, exposure to extreme temperatures represents a prominent problem, especially in regions such as the Mediterranean, characterised by high summer temperatures and low precipitation frequency.

People working outdoors or in poorly ventilated indoor workplaces are at increased risk of climate-related diseases.

Cold and sick leaves

Research on the effects of heat on public health has mainly focused on the analysis of extreme events, such as mortality and hospitalisations, not least because they are systematically collected. For example, in the field of occupational health, the impact of extreme temperatures, both hot and cold, on occupational injuries or kidney disease has been extensively investigated. However, its effect on the incidence of temporary incapacity (sick leave) is unknown.

Mireia Utzet and Amaia Ayala García, researchers at the Centre for Research in Occupational Health (CiSAL-UPF/IMIM), presented at this round table a recently published study whose objective was to evaluate the association between daily temperature and episodes of sick leave in Barcelona. In this study they found a higher number of sick leaves, mainly due to respiratory and infectious diseases, on cold days: from the second day after the day on which a low temperature was recorded, and up to six days later. On hot days, no association with the risk of sick leave was observed. This effect was observed especially in women and young people, and in non-manual and service occupations. The results point to the need to develop specific prevention plans for cold situations.

Enclosed and possibly poorly ventilated spaces during cold weather can help the spread of illnesses that can lead to sick leave.

Heat in schools

Schools are both educational and workplaces where exposure to high temperatures and thermal discomfort is increasingly frequent, intense and occurs earlier every year, at the beginning of spring. These centres are the only public buildings neither equipped nor adapted for optimal thermal comfort, as they were built at a time when they were supposed to be empty in summer, during the months of high temperatures. In addition, the buildings are often old and poorly insulated. However, children and teachers spend a large part of their day in classrooms and school playgrounds, so the school environment is crucial to ensure their health, well-being and effective learning, as well as the working conditions of school staff.

Mònica Ubalde, researcher at the Barcelona Institute for Global Health (ISGlobal) participated in the round table explaining a project carried out in primary schools in Barcelona, where they have investigated the relationship between the perception of indoor environmental quality and thermal comfort of teaching staff with the quality and productivity of work, and levels of student attention. The results of this study showed that, among primary school teachers, the perception of poor indoor environmental quality could be associated with lower productivity (reflected in prolonged periods of sick leave) but not with work quality. This perception was also associated with poorer concentration and attention span among pupils.

Schools – where teachers work and where children grow, play and learn – need to be adapted with effective and sustainable measures to mitigate the effects of climate change.

Heat and cancer

The health effects of extreme temperatures are diverse in scope and in some cases still unknown, including the long-term impact on non-communicable diseases such as cancer.

ISGlobal researcher Michelle Turner explained her study, included in the thesis of her PhD student Alice Hinchliffe, in which they assessed the associations between occupational heat exposure and the risk of breast and colorectal cancer in women in Spain, as well as the risk of prostate cancer in an analysis of three international studies. Possible interactions of occupational heat exposure with other occupational chemical agents were also assessed. The study results showed associations between occupational heat exposure and female breast cancer risk. In contrast, no associations were observed for colorectal or prostate cancer in the pooled analysis of men and women – but they were found for colorectal cancer among women.

Conclusion

Growing evidence on the effects of the climate crisis on working people points to a population that is highly vulnerable to the effects of the climate crisis. However, the range of exposures and health impacts is still unknown. There is an urgent need to implement surveillance measures that include occupational exposures caused by the climate crisis, such as extreme temperatures. This evidence is necessary for the development of preventive measures that take into account, in particular, vulnerable workers, so that the climate crisis does not represent a new axis of inequity in health.