Experts Discuss Impact of Climate Change on Health
In 2009, The Lancet, one of the oldest and most prestigious medical journals in the world, declared climate change to be the greatest public health challenge of the 21st century. Seven years later, it still is.
Above-average rain and heat in South America help mosquitos breed, contributing to the spread of the Zika virus, which is now found as far north as Puerto Rico. In June, the U.S. Centers for Disease Control and Prevention estimated that at least 20 percent of Puerto Rico’s 3.5 million residents will become infected with the mosquito-borne virus this year.
Extreme weather patterns are increasingly causing droughts, floods and wildfires. A relatively dry El Niño winter in parts of North America meant less snow, which in this year’s warm spring melted earlier than normal. That, in turn, created drier conditions that led to wildfires in Alberta, Canada, forcing the evacuation of 80,000 residents and destroying more than 1,000 square miles.
Amid these developments, Columbia’s International Research Institute for Climate and Society and the Mailman School of Public Health in June hosted a global colloquium on climate and health. The three-day meeting focused on infectious diseases, nutrition and the public health outcomes of meteorological disasters, seeking to build a global community of health practitioners and policy makers who use climate information to support delivery of health services and improve outcomes in the context of a fast-changing climate.
Among the speakers were Madeleine Thomson, a senior research scientist at the International Research Institute and an expert on the relationship between climate variability and health, and Patrick Kinney, professor of environmental health sciences at the Mailman School who has done pioneering research on climate change and urban smog and directs a new program in climate and health. Here, they discuss the symbiotic relationship between climate and health.
Q. What is the biggest concern about climate’s effect on public health?
Patrick Kinney: Right now, the largest risks to health have to do with extremes of climate—big coastal storms, like Katrina or Sandy, or periods of unusually hot weather, like the deadly European heat wave of 2003, which caused about 35,000 deaths. Climate change is making these events more extreme—that is, outside of our historical experience and ability to easily prepare for and rebound from. Over the long run, these risks will increase as we experience wider swings in climate. In addition, climate change will lead to longer and more severe droughts in some regions, leading to crop failures and famine.
Madeleine Thomson: Climate predominantly affects poor populations in rural areas who do not have the capacity to protect themselves from their environment or smooth the disruptions to their health and livelihood brought about by seasonal changes and climate shocks. There also are less obvious effects. Birth weight, for example, is the single most important determinant of infant mortality and healthy development of children. In many parts of the world, birth weight varies significantly by season, especially in regions that depend on rain-fed rather than irrigated agriculture. The period between planting and harvesting in these regions is widely known as the “hungry season.” During this time, women of reproductive age— including pregnant and lactating women—often have reduced nutritional intake and higher rates of water-borne diseases that affect fetal and early childhood development.
Q. How does the impact of long-term climate change compare with the effects of seasonal fluctuations in weather?
Thomson: Long-term trends in climate have many and varied effects on health that are not easy to predict and can come through indirect routes such as the impact of climate on local and national economies and migration. Others will be more direct, involving changes in the distribution of certain diseases, reductions in food supply in areas of the world that are already food insecure, or an increase in such meteorological disasters as droughts, floods or heat waves.
Q. How do these issues vary around the world?
Kinney: The impacts will likely be much greater in developing countries, due to their more limited resources and greater dependence on local climate for livelihoods.
Thomson: In developed countries, we protect ourselves from the climate in numerous ways. We have well-built houses with insulation and air conditioning, early warning systems for floods and hurricanes, well-funded programs and health services that deal effectively with the prevention and management of climate-sensitive diseases. All of these may be lacking in developing countries, which are often in the tropics. Hot and humid climates are particularly favorable to vector-borne and water-borne diseases.
Q. How does climate affect the spread of the Zika virus and other diseases?
Thomson: Climate is an important driver of Zika virus transmission. High rainfall may result in an increase in outdoor breeding sites for the mosquitos that are Zika vectors, while drought years may result in increased water storage, and thereby increase mosquito-breeding sites. Warming temperatures also increase the development rates of both vector and virus. Zika was introduced and has spread in Latin America during a period of prolonged drought and at a time when the region’s temperature has been anomalously warm.
Q. What are some other public health issues involving climate?
Thomson: Climate’s impact both on agricultural productivity and food-supply chains affects the quality and price of staples. Price increases force the poor to make choices that often include elimination of more expensive, more nutritious foods. More than a billion people are affected by malnutrition, both stunted growth and obesity. Many also suffer the less obvious impact of micro-nutrient deficiencies; for example, they lack iron or zinc, resulting in weak immune systems and anemia. And, of course, all forms of malnutrition make individuals more susceptible to ill health—whether from infectious or non-communicable diseases. Before considering what we might do to prevent climate-sensitive health outcomes in the future, it is essential to better manage those of today. Climate information can be used as a resource in this process
Q. Can public health systems cope with the challenge?
Kinney: In developed countries, coping should be possible, although there is a need for training public health professionals. Health systems in developing countries already are under stress and climate change will exacerbate those stresses. Research plays a key role in identifying and quantifying current risks and in estimating future impacts. This is critical for planning, so that new investments can be directed where they can have the most impact.
Q. It has been said that solving the climate crisis could reap huge benefits for public health. Can you explain?
Kinney: One of the most important insights to emerge from recent scholarship has been the realization that policies to address climate change can bring simultaneous benefits for human health. For example, commuting by bike instead of car reduces greenhouse gas and air pollution emissions while improving heart health. Eating a diet lower in red meat also brings huge personal health benefits as well as reducing methane emissions from livestock production.
Q. Much of your research has been on the effects of air quality on public health. How does that relate to climate?
Kinney: Climate and air quality are intimately connected. Many of the same fossil-fuel burning sources that are responsible for climate change also put out pollutants that are directly harmful to human health. And as the climate changes, so, too, do patterns of air quality.