Hot, humid conditions during pregnancy undermine child health much more than heat alone, according too new research.
The dangers of heat and humidity are so well known it’s become cliche to mention them. But the impacts can extend farther than even scientists and doctors realized.
In a paper in Science Advancesresearchers looked at the effect of prenatal exposure to extremely hot, humid conditions on the health of children in South Asia.
They found that humidity worsens the impacts of heat exposure, in part as it prevents pregnant women from cooling down. Accounting for humidity quadrupled the effect of extreme heat on child health.
“Exposure to hot, humid conditions in-utero is perilous for child health, and more dangerous than just hot temperatures alone,” says lead author Katie McMahon, a doctoral student under Professor Kathy Baylis in the geography department at UC Santa Barbara.
By focusing on the effects of temperature only, many researchers, doctors and public health officials may be underestimating the true impacts of extreme weather. This is particularly concerning given that these conditions are predicted to become more frequent and extreme due to climate change. What’s more, some of the most densely populated regions on Earth are hot, humid areas along rivers and coastlines. Populations are also growing rapidly in many of these locations.
Fortunately, understanding this phenomenon can help guide interventions. Even simple actions could have notable benefits, the authors claim.Humidity in the forecast doesn’t just make heat more miserable; the “feels like” temperature has an actual basis in our biology. Humans cool by sweating. but evaporation slows when air is humid.”And when evaporation can’t happen, then cooling can’t happen,” McMahon says. “All that heat builds up in our bodies, causing heat stress.” And this can happen at much lower temperatures under humid conditions.
That’s why the wet-bulb globe temperature (WBGT) was invented in the 1950s. Unlike a simple temperature measurement, this metric accounts for four of factors that affect heat stress: air temperature, humidity, radiant heat sources, and airflow. This is precisely what McMahon and her coauthors tracked in their investigation.
As for the health effects,the authors looked at height-for-age: a ratio of a child’s height compared to the average for their age. This ratio is a commonly-used indicator of chronic health status for children under age five.
The researchers culled data on child health data from the Demographic and Health Surveys (DHS), a large-scale and complete household survey of public health and demographics. Their daily weather data was produced by the Climate Hazards Center at UCSB.Much of the work involved linking demographic data and surveys with heat and humidity data to identify prenatal heat exposure. After this, the authors ran the data through their statistical models with carefully selected temperature, humidity and growth thresholds.
These thresholds were 35° Celsius (95° Fahrenheit) for temperature and 29° C (84° F) for WBGT.
Rising heat and Humidity Pose Significant Threats to Health, Especially for Vulnerable Populations
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Recent research highlights the escalating dangers of extreme heat, particularly when combined with high humidity, and its disproportionate impact on pregnant women, infants, children, and outdoor workers. While the findings are concerning, researchers emphasize that targeted interventions – from improved forecasting to public health messaging – can significantly mitigate these risks and build resilience.
The Growing threat of Heat and Humidity
A study from UC Santa Barbara, and ongoing work at the Climate Hazards Center, reveals that the combined effect of heat and humidity is far more detrimental to health than heat alone. This is particularly critical during pregnancy, where exposure to high heat and humidity can negatively impact child health. The research underscores a troubling trend: as climate change intensifies, these conditions are becoming more frequent and severe, creating vicious cycles of vulnerability. However, researchers are optimistic that these cycles can be reversed with strategic interventions.
Understanding the Science: WBGT and Compounding Hazards
Researchers are focusing on the Wet Bulb Globe Temperature (WBGT), a measure that combines temperature, humidity, wind speed, sun angle, and cloud cover to assess heat stress. https://www.weather.gov/ama/wbgt WBGT provides a more accurate picture of how the human body experiences heat than temperature alone.
Beyond the direct impact of heat and humidity, scientists are also investigating how these hazards compound with others, such as air pollution. understanding these interactions is crucial for developing effective protective strategies. For example,exposure to both heat and air pollution can exacerbate respiratory and cardiovascular problems.
Early Warning Systems and Forecasting Improvements
The Climate Hazards Center is actively developing and implementing extreme heat forecasting and early warning systems. A key project involves collaboration with the Kenyan meteorological department to improve forecasts for the Kakuma refugee camp in northern Kenya. By tracking WBGT, camp administrators can implement adaptive measures – such as providing cooling centers and adjusting work schedules – when a heatwave is predicted.
To enhance forecasting accuracy, the center is partnering with Microsoft’s AI for Good Lab to leverage machine learning for weather modeling, specifically tailored to the conditions in refugee camps. https://www.microsoft.com/en-us/ai/ai-for-good This collaboration aims to provide more precise and timely warnings, allowing for proactive responses.
Focusing on Vulnerable Populations
Researchers are dedicating efforts to pinpointing the most vulnerable groups and understanding the nuances of their exposure.
* Mothers, Babies, and Children: Studies are underway to determine which mothers and children are most susceptible to the adverse effects of heat and humidity, and how these vulnerabilities may change in the future.
* Farmworkers: Researchers are quantifying the health impacts of heat stress on farmworkers in California’s Salinas Valley. This work, conducted in partnership with local health clinics, will build upon existing qualitative studies to provide concrete data on heat-related medical visits. https://www.cdph.ca.gov/Programs/climatechange/Pages/Heat-and-Health.aspx Heat stress among farmworkers is a well-documented issue, and this research aims to inform targeted interventions.
Key Takeaways
* The combination of heat and humidity poses a significant and growing threat to public health.
* Vulnerable populations – pregnant women, infants, children, and outdoor workers – are disproportionately affected.
* Early warning systems, improved forecasting, and targeted interventions can mitigate these risks.
* Understanding how hazards compound upon each other is crucial for developing effective protective strategies.
Looking Ahead
The research presented is a stark reminder of the challenges posed by a changing climate. However, the emphasis on proactive interventions and the collaborative spirit of researchers offer a path toward building more resilient communities. Continued investment in forecasting technology, public health messaging, and targeted support for vulnerable populations will be essential to safeguarding health in a warming world.