A warmer, wetter world will mean more work for internists

By now, environmental research has found evidence that our planet is warming and our polar ice caps are melting. The most popular methods of reducing the impact on the environment, from driving hybrids to using fluorescent light bulbs, have also been heavily publicized.

But what does this environmental crisis mean for internists? Medicine and the environment, a new department in ACP Internist, will analyze the planet's impact on medical practice and conversely, medicine's impact on the environment. The feature launches this month with an investigation of the health impacts of climate change.

Predicting the health impacts of climate change is an inexact science, experts in the field say, although they agree with leaders of the U.S. health community that the expected warming of the planet will cause changes in human health.

Howard Frumkin, MD, director of the CDC's Center for Environmental Health, recently told Congress that there was strong evidence that climate change would affect public health, and the American Public Health Association chose climate change as its theme for National Public Health Week 2008.

“This will be a very big issue for all of us in health care,” said Dr. Frumkin. “There's some evidence that changes are already underway.” He noted that 150,000 annual deaths could be attributed to climate change since 2000, according to estimates from the World Health Organization.

However, understanding the specifics of how, where and when climate change impacts health is the tricky part, according to Michael T. Osterholm, PhD, director of the Center for Infectious Disease Research and Policy. “The world is clearly warming up, but it's not warming uniformly. We don't know where it's going to warm, and we also don't know where the precipitation changes are going to be. None of us know yet,” he said.

Scientists do have some idea of the possible effects, and the threats break down into two main categories, according to Gina Solomon, MD, senior scientist at the Natural Resources Defense Council. “There are the high-probability, moderate-impact health threats and then the low-probability, high-impact health threats,” she explained.

Physicians and other health care providers should be preparing for the most likely results and at least aware of the risk of the less probable, but more dramatic threats, experts said.

Hot, hot, hot

Dr. Solomon has concentrated her work on one of the most likely consequences of climate change—more extreme heat events. “Increasing heat waves are very high probability, in fact almost certain to occur given all of the climate scenarios, something that we should certainly be prepared for in the health care community,” she said.

According to the U.S. Global Change Research Program (a government research initiative), climate change is expected to increase the annual excess summertime mortality in the U.S. several-fold by 2050, from 500 to 1,000 deaths for New York City alone.

The key to preventing heat-related illness and death is advance communication between high-risk patients and physicians. Those at highest risk include outdoor laborers and people over age 65 who are living alone in poverty.

“Those are the people who are in our practices, so we can get to them. Every health care worker in the country should know how to counsel patients in the early part of the summer about what to do in an extreme heat event,” Dr. Solomon said.

Patients who are at risk should be questioned about their access to air-conditioning and assisted in developing a plan for a heat emergency.

In the future, patients with asthma and allergies will also need to plan ahead, because the U.S. is likely to see more low air quality days. Increased ozone formation is an expected result of climate change, and that ozone will mix with sunlight and pollution to raise the intensity and prevalence of smog, Dr. Solomon said. “Ozone is a known asthma trigger. There is evidence showing that it may also be a cause of asthma in kids,” she said.

Researchers have found one thing that the excess carbon dioxide in our air is good for, and that is weed growth. A study by Dr. Epstein and colleagues, published in the Annals of Allergy, Asthma and Immunology in 2002, compared ragweed raised in present-day air and with plants grown in carbon dioxide concentrations expected in the next 50 years.

“What they found is that CO2 acts as a fertilizer, especially for weedy plants. Not only did the ragweed grow faster and lusher but it also created far more pollen per plant,” said Dr. Solomon. In addition, Lewis Ziska, PhD of the USDA has demonstrated that the proteins in the pollen grains are also more allergenic.

The implications for internists are more visits from patients suffering from allergies. “As clinicians, we should be anticipating more and more bad air days and potentially worse seasonal allergy disorders,” Dr. Solomon said.

And since Dr. Ziska has shown that poison ivy responds to carbon dioxide much like ragweed, it can also be expected to cause more problems.

Unnatural disasters

Just as expected but harder to prepare for is the predicted increase in extreme weather and natural disasters due to climate change. Hurricanes, flooding and drought are all public health risks posed by a warming planet, experts said. “Most of that's likely to occur in developing countries, the ones least prepared to deal with it,” said Dr. Osterholm.

Changes in the habitability of some areas due to permanent flooding or drought could also lead to mass migrations and accompanying spreads of infectious diseases. “You have to move potentially millions if not billions of people around the earth. That could very easily result in a much higher rate of infectious diseases because of the very nature of migration,” Dr. Osterholm said.

Developing defenses and responses to these sorts of problems is out of the scope of practicing internists, the experts acknowledged. The CDC is looking at such preparations, said Paul R. Epstein, MD, associate director of the Center for Health and the Global Environment at Harvard Medical School.

However, there are some specific diseases and conditions that internists can expect to see more of as the world warms and migration patterns widen.

For example, the ticks that carry Lyme disease may expand their habitat. “The projections are that it will move into higher latitudes, into northern Maine and Canada by later in this century. There are signs that these shifts are underway,” said Dr. Epstein.

Outbreaks of water-borne diseases like toxic Escherichia coli and cryptosporidium could also result from the expected alterations in weather patterns, the experts predicted. Vector-borne diseases such as West Nile virus (WNV) are also likely to respond to changes in climate around the U.S. “The explosive debut of WNV in New York City in 1999 may be related to the drought and July heat wave that enveloped the East that summer. It's the unstable weather patterns that can lead to higher populations of mosquitos,” said Dr. Epstein.

Warming-related mosquito migrations have already been accused of new outbreaks of infectious disease, although that is one of the most contentious issues in climate change research. An Italian outbreak of chikungunya, a traditionally African disease, was originally attributed by some to climate change, but other scientists argued that far too many other confounding factors existed to develop a direct causal connection.

The debate on this outbreak indicates that uncertainties remain about the health effects of climate change. Will there be U.S. outbreaks of dengue fever and other traditionally tropical diseases? If that happens, is it definitely a result of climate change? No one knows, said Dr. Osterholm. “On the whole, a warmer, wetter world likely means more infectious diseases. It's just that where it's going to happen, we don't know yet. More now than ever, we need very much to boost our public health surveillance,” he said.

Dr. Solomon seconded this assessment. “Improving our public health infrastructure would go a long way to being prepared for whatever global warming throws at us, whether it's more Katrinas or drinking water problems or heat waves,” she said.

Of course, there's also work to be done about climate change on an individual level.

“The more I learn about this issue, the more concerned I become about the next 50 to 100 years. The amount of greenhouse gases in the air is enough to commit us to pretty serious global warming even if we reduce emissions now. If we take aggressive steps to reduce greenhouse gas pollution, we can still avert the worst of the health impacts,” Dr. Solomon said.