Water is everywhere in the aftermath of Hurricane Sandy - in basements, on the streets and in transit systems - but the one place that flood water is most dangerous is in your body.
ABC News chief health and medical editor Dr. Richard Besser collected floodwater and drinking water in some of the areas hit hardest by Sandy and had them tested at The Ambient Group lab. The floodwater collected in Lower Manhattan tested positive for gasoline and two types of bacteria found in sewage: E. coli and coliform.
"Very dangerous," Besser said. "Make sure you wear protective gear if you are coming into contact with flood water."
Looking at the testing containers filled with Manhattan floodwater, Besser explained that the yellow glow indicated that coliform bacteria was present at high levels. The purple fluorescence tells us that there are sky-high levels of E. coli from sewage contamination.
Today, he went to Piermont, N.Y., an area hit so hard by the hurricane that it's under a boil water advisory, meaning residents are instructed not to drink tap water without first boiling it or purifying it with bleach.
When a power outage knocked out one of Piermont's water pumps, officials were concerned about tap water contamination. The water company tested water from a hydrant, which initially ran brown, but eventually cleared.
Besser tested the hydrant water as well, and smelt chlorine in it, which helps protect it from bacteria.
He also collected tap water from a family's home faucet and expects to review the lab results tomorrow which will indicate whether the family's water was contaminated. Several families in the neighborhood are already boiling their water as a precaution.
Anyone in a flood-affected area should listen for alerts. While water companies are responsible for alerting residents whether their water is unsafe to drink, city officials also alert the community.
New York City, for instance, the Department of Environmental protection announced today that its water is safe to drink. Water in reservoirs 125 miles north of the city continue to be monitored closely with extra testing in the wake of the storm.
If you rely on well water and were in a flooded area, you should assume your water is contaminated until it can be tested. Follow the "boil water" advisories and boil your water for a full minute before using.