Harvey’s unprecedented floods bring a looming public health crisis

Public health risks will remain long after the water recedes.

Rescue boats help flood victims evacuate as floodwaters from Tropical Storm Harvey rise Monday, Aug. 28, 2017, in Houston. (CREDIT: AP Photo/David J. Phillip)
Rescue boats help flood victims evacuate as floodwaters from Tropical Storm Harvey rise Monday, Aug. 28, 2017, in Houston. (CREDIT: AP Photo/David J. Phillip)

Rain continues to fall on the Texas Gulf Coast and Houston, fueling catastrophic flooding that the National Weather Service has described as “unprecedented” and “unknown and beyond anything experienced.”

At least 15 people have died from storm-associated flooding, and days more of forecasted rain means the severe flooding that has inundated hundreds of homes is likely to continue. Houston meteorologist Tim Heller told Grist that the situation was “worse than the worst,” and described “area flooding, regional flooding” that could keep parts of the city underwater for months.

But if past major flood events are any indication, Houston and other towns are merely beginning to contend with the public health impact that comes when homes and businesses are left underwater for days, weeks, or even months — from the immediate risk of inundation and drowning to the much more insidious risks that come from living in the midst of one of the most devastating floods in U.S. history.

In an industrialized context, in a place like the U.S., we’re mainly concerned with injury and mortality in the short term, and mental health effects in the long term,” Sabrina McCormick, an associate professor of environmental and occupational health at George Washington University, told ThinkProgress. 

According to McCormick, several factors influence the specific mix of public health concerns that can arise after a flood in an industrialized area. The primary factor is the speed of inundation; the quicker floodwaters rise, the more likely it is that public health response systems, like hospitals, will become either overwhelmed or inaccessible.


A more gradual flood is generally just safer, largely because it results in a smaller number of injuries and the response systems can get into gear in a way that can manage the event better than when it is like it is now, when it is extremely fast and extremely intense,” she said. “That kind of event is more dangerous.”

Houston residents who evacuated in floodwater — some wading up to their waist — were met with a mix of sewage, oil, and gasoline. Exposure to raw sewage can lead to gastrointestinal disease, if an evacuee comes into contact with contaminated water and either does not have a chance to wash their hands before eating and drinking, or has open wounds while wading through the water. Sewage can seep into floodwater when homes are inundated and plumbing breaks, or when sewage treatment plants themselves are inundated. In the wake of Hurricane Sandy, a sewage treatment plant that had lost power during the storm discharged billions of gallons of untreated sewage into Newark Bay.

“Sewage treatment plants are especially vulnerable to flooding and storm surge,” Judith Enck, former EPA regional administrator that coordinated the agency’s response to Sandy, told ThinkProgress.

Post-Hurricane Katrina, there were 22 cases of waterborne infections, five of which resulted in deaths. According to the Centers for Disease Control, however, the vast majority of those cases were caused by exposure to bacteria through a wound, not from drinking contaminated water.

As of Tuesday, the Addicks Resevoir — a major reservoir meant to protect downtown Houston from flooding — breached for the first time in history, likely bringing some of that water into contact with contaminated floodwater. Houston officials have asked residents to minimize tap water use, as at least one water treatment plant is underwater due to flooding.

Still, McCormick said that widespread illness due to contaminated water is rare in industrialized countries.

If the healthcare system and response system is totally overwhelmed, then we may see outcomes that are unusual, which would be something like contamination of food and water from the flood itself,” she said. “But that’s not my first concern.”


Another factor that could determine the extent of Harvey’s public health impact is how long water remains stagnant in homes and businesses. Even after it has receded, stagnant water is hospitable to things like mold and mildew, which can be a serious health hazard both for people returning to the buildings and cleanup crews. The CDC recommends that anything tainted by floodwater — including carpeting, insulation, and drywall — be removed from homes, which leaves low-income communities that might lack the resources to completely replace their homes especially vulnerable to adverse health impacts associated with mold and mildew.

“It depends a little bit on how long this water stands stagnant, but we saw in the case of Katrina long-term damage to homes that included things like black mold that are actually quite dangerous to cleanup crews,” McCormick said. “If we were to see something like that, then there could be longer-term risks associated with the effects of the water.”

Stagnant water can also become a breeding ground for disease-carrying vectors like mosquitoes. Houston has seen six confirmed cases of Zika this summer, though all cases were travel-related. Texas has also seen cases of West Nile regularly since 2002, with 36 confirmed cases so far in 2017. Directly after an extreme flood event, mosquito populations can actually decrease, as waters wipe out existing breeding sites. In the months after a massive flood, however, water leftover from the disaster can create breeding grounds for mosquitoes that cause populations — and mosquito-related illnesses — to spike.

According to a list released earlier this year by Orkin, Houston is the seventh worst city for mosquitoes in the United States. Houston is also weeks away from the end of peak mosquito season, meaning that the insects will likely have plenty of time to breed after the flood waters have receded. As with the storm itself, which was intensified by climate change, mosquito breeding also has a climate component: warmer temperatures allow mosquitoes to survive and reproduce longer into the year, leading in turn to an increase in mosquito-borne illnesses. If temperatures in Houston remain warmer than average in the weeks and months after the floodwaters recede, that could mean more mosquitoes and more mosquito-related illness.

You can say, generally, that this kind of flooding will have some kind of effect on mosquitoes, both in habitat and related-patterns of mosquito bites,” McCormick said.

Because Houston is a major hub of the United States petrochemical industry — Houston’s Shipping Channel is home to the country’s largest refinery and 30 percent of the country’s refining capacity — the area is especially vulnerable to environmental disasters like an oil spill or chemical discharge that could also have serious public health implications. Residents of La Porte and Shoreacres, communities just to the southeast of downtown Houston, were asked to shelter in place Monday afternoon through Monday evening due to a chemical spill from a ruptured pipeline.

Several fossil fuel companies have made decisions to shut down their refineries in the midst of the flooding and widespread damage in the surrounding areas. These include Shell’s Deer Park refinery in Houston, which is capable of handling 340,000 barrels of oil daily, and Exxon’s Baytown refinery, which can handle up to 560,000 barrels per day. Residents living near the refineries have reported the presence of “unbearable” smells wafting from the petrochemical facilities, possibly because shutting down facilities causes them to release thousands of tons of air pollutants.


Meanwhile, the Texas Council on Environmental Quality has shut off its air quality monitors in an effort to protect them from potential wind or water damage. That means that it’s up to petrochemical companies to report emissions of pollutants from their facilities, leaving communities near these facilities — largely minority and low-income — largely uninformed about potentially dangerous pollutants in their air.

Ultimately, public health experts like McCormick hope that when the flood waters recede from Harvey and the damage is surveyed, coastal communities and vulnerable cities take a look at what could be done to help prevent another disaster of this scale. With climate change fueling more powerful storms, and development paving over natural flood barriers like wetlands, the answer is likely to be found in combination of better resiliency planning and serious greenhouse gas mitigation, two policies the Trump administration is loathe to pursue.

Still, McCormick cautions that enacting these policies and planning strategies now can save lives in the future.

This is a lesson to be heeded for all of the coastal zones in the southern United States that stand similar risks, that they really need to be paying attention to and preparing for events like this in the future,” she said. “The preparation can mean that a lot of lives are saved, a lot of property damage is averted, and therefore we can protect people from these really problematic mental health outcomes when people’s livelihoods and lives are destroyed and upended.”