What a microbiologist wants you to know about floodwater

Microbiologist and immunologist Michael Schmidt, Ph.D., doesn’t mince words when it comes to what floodwater might contain. “My rule of thumb is if it's standing water, you assume it's full of fecal material. When in doubt, assume the worst.”

The water may not be full of sewage, but Schmidt said it’s smart to be careful. That could be important advice as the Charleston area recovers from Tropical Storm Debby’s heavy rain in the middle of hurricane season.

Schmidt, a professor in the College of Medicine at the Medical University of South Carolina, said his biggest concern involves families with septic systems. “If the septic system overflows, that, of course, is a hazard because it's sewage, and you don't want the kids running around in sewer water.”

If people do come into contact with contaminated water, it can cause a range of health issues. “If you happen not to wash your hands before eating, you could effectively contaminate yourself and feel unwell with an upset stomach and diarrhea. And if you have any open sores on your body that happened to encounter the sewage, that could also cause an infection at that site,” Schmidt said.

Sewage isn’t the only concern. Floodwater can also contain a host of other hazards, according to the Centers for Disease Control and Prevention. They include:

• Downed power lines.
• Household, medical and industrial hazardous waste (chemical, biological and radiological).
• Coal ash waste that can contain carcinogenic compounds such as arsenic, chromium and mercury.
• Other germs and contaminants that can lead to illness.
• Physical objects such as lumber, vehicles and debris.
• Wild or stray animals such as rodents and snakes.

Schmidt encouraged people to check out this CDC infographic, which has advice about safe hygiene and how to clean areas of a home that flooded. And he had some advice of his own. 

“Good old house bleach diluted with water is one of the best ways of cleaning your house after a flood. And not all bleach is created alike. The Canadians have created a handy-dandy bleach calculator, where you literally read the back of the bottle, plug in the numbers, tell them how much you want to make and it tells you how many caps of bleach to add.” 

Schmidt said people should also be aware that contaminants in floodwater can affect coastal creatures such as oysters. “You generally have to allow them to purge themselves to make them safe for consumption. So you let them sit in clean water; you change the water a number of times. Remember, they're filter feeders. Yeah. So they literally filter the water; so they actually clean up the water, and they're eating the microorganisms. They're eating the plankton and the other things in the water column.”

A different kind of creature may become an issue, too, but for a different reason. “With the flooding we’ve seen, I worry about mosquitoes. They breed in standing water. Mosquitoes can transmit disease,” Schmidt said.

To control mosquitos, the CDC recommends that once a week, people empty items that hold water. That can include tires, buckets, toys, pools, birdbaths, plant pots and trash cans.

But Schmidt said it’s important to keep things in perspective in the aftermath of a storm that hit some areas much harder than others. “Fortunately in the Lowcountry, we've only seen the standing water. We haven't seen the great consequences like they have seen in Florida, where they needed boat rescues.”