By Hugh J. SealyNearly 2 million Americans live within a mile of a highly polluted Superfund site that's at risk of flooding due to climate change. A flood at any of these 327 locations could spread toxic waste to the surrounding community, according to an Associated Press analysis. This report shows that climate change isn't just a long-term environmental challenge. It's also an urgent public health threat.Superfund sites are places -- such as old landfills and shuttered chemical plants -- that the Environmental Protection Agency has singled out for federal clean-up due to the presence of toxic materials. Climate change-fueled storms have turned these sites into public health disasters waiting to happen. In Houston last year, 13 Superfund sites flooded as a result of Hurricane Harvey. One of those locations, the San Jacinto Waste Pits, leaked toxic chemicals including dioxins, which cause reproductive problems and cancer. Meanwhile, in the wake of Hurricane Maria, a lack of clean water in storm-battered Puerto Rico forced some residents to drink from wells near the island's Superfund sites. Stories like these will become far more common, especially as climate change increases the risk of flooding. A recent study published in the journal Science Advances predicts that, by 2040, the number of people in North America vulnerable to extreme flooding will balloon from 100,000 to one million. Floods aren't the only calamity caused by climate change. Toxic air pollution from wildfires, which are exacerbated by droughts linked to climate change, also endangers Americans' health. The hotter temperatures brought on by climate change have led to longer and more severe wildfire seasons. This is especially true in the western United States, as evidenced by last year's devastating blazes in Southern California. Those fires destroyed over 1,000 buildings and forced hundreds of thousands of Californians to flee their homes. The damage wasn't limited to Southern California. Wildfires release toxic heavy metals into the air. Such pollutants can make the air dangerous to breathe up to 70 miles away. Climate change also enables diseases to spread further and more rapidly. As temperatures rise, animal-borne diseases that were previously confined to the tropics and subtropics move north. Since the 1980s, 76 percent of large American cities have experienced longer mosquito seasons, in part due to warmer, more humid climates. This trend helps explain why the incidence of West Nile virus, which is carried by mosquitoes, has skyrocketed from only 21 cases in 2000 to 2,149 in 2016. Worst still, the likelihood of contracting West Nile virus will rise in 68 percent of California's geographic areas by 2050, according to researchers at UCLA. Similarly, climate change has made the United States more hospitable to several tick species that carry Lyme disease. Since 1996, the number of counties in which these ticks live has increased by 44 percent. Twenty years ago, these insects could not be found anywhere in Ohio. Today, they live in 33 of the state's 88 counties. Many people think of climate change as a long-term problem, the costs of which will be paid mainly by the planet's future inhabitants. But this view ignores the urgent threats that flooding, wildfires, and diseases caused by climate change pose to Americans right now. Climate change demands an immediate response.Sealy is a professor in the Department of Public Health and Preventive Medicine at St. George's University in Grenada. He has been a lead negotiator for small island states since 2008, including at the historic COP 21 in Paris, the COP 22 Summit in Morocco, and COP 23 in Bonn.