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May 2001 


A research team composed of health scientists from academia, government, and private industry has released its assessment on climate change health impacts in the United States. The report makes clear that if the United States is to be prepared to meet the increased health challenges posed by global climate change, it must improve the nation's public health infrastructure, better protect vulnerable populations, and increase research efforts to fill crucial knowledge gaps about the connections between climate and health.

The assessment, mandated by Congress and sponsored by the U.S. Environmental Protection Agency, was led jointly by scientists at the Johns Hopkins Bloomberg School of Public Health and the Centers for Disease Control and Prevention (CDC). It identifies and examines five key problems influenced by current weather extremes, or future global climate change: heat-related illness and death; health effects related to extreme weather events; health effects related to air pollution; water-borne and food-borne diseases; and vector-borne and rodent-borne diseases. Six papers that buttress the report released earlier this year appear in a special May supplement issue of Environmental Health Perspectives.

"This assessment is not one of doom and gloom, but does warrant concern within the public health community," said Jonathan Patz, MD, MPH, an assistant professor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health, and co-chair of the assessment. "Our group found that while much of the U.S. population is relatively protected against climatic hazards, there remain vulnerable segments of the population at risk." Among these groups are the poor, the elderly, children, and those whose immune systems are compromised by disease.

Patz emphasized that a unique cross-section of academic, government, and industry scientists was involved in writing the report. "The author team was chosen both for expertise and range of opinions and perspective on the subject; in the end, we arrived at a true consensus document." He stated that the team solicited and incorporated concerns of stakeholders and many outside scientists during an extensive and lengthy peer review process.

The report makes clear that maintenance and improvements in the public health infrastructure are essential. For example, more than 950 communities in the United States currently have combined sewer systems that service both sewage and storm water runoff. During periods of heavy rainfall, expected to increase as the earth warms, these systems discharge excess wastewater directly into bodies of surface water that may be used for drinking. Other needed improvements, according to the report: improved early warning systems for severe weather and pollution; better urban planning, with stricter zoning and building codes to minimize storm or flood damage; increased use of mass transit to reduce urban air pollution; improved disease surveillance and prevention programs; and further education of health professionals and the public about climate/health risks.

Speaking of vulnerable U.S. subpopulations already at increased risk from pollution and other hazards, Susan Bernard, JD, MPH, an instructor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health and lead author on two of the papers, said, "We know that the people most at risk in heat waves, for instance, are the poor urban elderly, especially those who are chronically ill or isolated. Deadly heat waves are already common in summer and may become more so in the future, yet many locations lack effective programs to prevent such deaths."

Of climate change's effects on air pollution, Jonathan Samet, MD, professor and chair of epidemiology at the Johns Hopkins Bloomberg School of Public Health and co-author of the report said, "Warmer and more variable weather may cause increases in ground-level ozone, which could adversely affect lung health."

"The relationship between weather and specific health outcomes is still not well-understood for many diseases," said Patz. "Addressing major knowledge gaps would allow us to be better prepared in the future." Among the areas where further research is needed: the relationship of weather to influenza and other causes of winter mortality; the linkages between climate, altered ecology, and infectious disease transmission; and the impacts of land use and agriculture on water quality.

The health assessment was sponsored by the U.S. Environmental Protection Agency, Global Change Research Program. Download climate change brochure

Figures from the summary report may be downloaded from

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