Interview: Heat stress and other impacts of the climate emergency threaten public health

Increased hospitalizations and mortality from cardiovascular and respiratory diseases. Spread of vector-borne diseases. Food insecurity and malnutrition. Mental health issues. These are some of the health impacts of the climate emergency that can already be observed, says Sandra Hacon, a researcher at the Sergio Arouca National School of Public Health (Ensp/Fiocruz). The professor also lists a series of signs and symptoms associated, for example, with heat stress, which occurs due to rising temperatures, such as during heat waves: dizziness, feeling faint, nausea, headache.

"We are already experiencing a climate emergency. Forecasts already point to increased heatwaves, heat stress and rising temperatures. We are already seeing all these changes. The health sector must urgently structure itself to train its professionals and create logistical and infrastructural conditions to meet the 'new normal' to avoid an increase in illnesses, hospitalizations and deaths due to the temperature rise," she explains.

Hacon also points out that the impacts affect populations in different ways. Considering the complexity of Brazil's social structure, with marked social inequality, the researcher states that there are "a variety of negative impacts on public health, of different magnitudes for the exposed populations". According to her, low-income communities, children, the elderly and pregnant women are the most vulnerable groups.

Informe Ensp: Why does climate change pose a risk to human health, especially in tropical regions?

Sandra Hacon: The implications of the climate emergency for the health of the population are a significant threat. The social structure of the Brazilian population is extremely complex, with a high degree of social inequality. This implies a variety of negative impacts on public health, of different magnitudes for the exposed populations and with different priorities at the institutional level for the health of the Brazilian population.

The impacts of the climate emergency on human health have different severities depending on the degree of vulnerability of the exposed communities.

Informe Ensp: What are the potential health risks of heat stress?

Sandra Hacon: The health risks associated with heat stress (the technical term for the impact of rising temperatures on the human body) depend on the conditions of exposure (continuous or intermittent), duration and frequency, pre-existing health conditions, environmental conditions, social conditions (place of residence, income, education, access to health services) and genetic factors. But generally, the most vulnerable groups are the hardest hit, i.e. those who suffer the most, such as low-income communities and children, due to their still-developing homeostasis balance. As well as the elderly, as they often have difficulty maintaining their homeostasis balance and dehydrate more easily. The same goes for pregnant women who need to keep their blood pressure and fluid intake in balance, which is often not possible.

Some of the impacts of heat stress are: homeostatic imbalance in the body, with signs and symptoms such as dizziness, fainting, nausea, headache and an increase in hospitalizations and mortality from cardiovascular and respiratory diseases. Hemodialysis patients, for example, must control their blood pressure and keep their bodies hydrated. This group is at high risk in a heat stress scenario.

Informe Ensp: 2024 was a year marked by several "heat waves" across the country, especially in Goiás. In the future, what impact could these heat stress conditions have on the health of the population?

Sandra Hacon: As has already been mentioned by the media and some researchers, we are already experiencing a climate emergency, in which the "new normal" brings countless impacts to the Brazilian population. Some of these are already predicted by information centers that work to characterize the present climate and its long-term variability, in addition to carrying out studies to project future climate scenarios to predict the impacts in the 21st century.

Forecasts already point to an increase in heatwaves, heat stress and rising temperatures. We are already seeing all these changes. The health sector must urgently structure itself to train its professionals and create logistical and infrastructural conditions to meet the 'new normal' to avoid an increase in illnesses, hospitalizations and deaths due to the temperature rise.

Informe Ensp: What are the challenges for health services and professionals in dealing with high temperatures, in terms of identifying the signs and symptoms caused by heat stress?

Sandra Hacon: The main challenges are related to mitigation and adaptation across Brazil's 5,570 municipalities, which are at different stages of infrastructure and logistics, limited expertise in a relatively new field (the impacts of heatwaves and heat stress), lack of sanitation in 50% of municipalities and traditional communities in remote areas. Other challenges include the frequency of intense storms, which threaten the health through adverse changes, increased air pollution and the spread of vector-borne diseases, such as dengue fever, which has reached 6 million cases in Brazil. Food insecurity and malnutrition, in addition to mental health issues, are already problems associated with the climate emergency.