Toxic Stew
Karen Mancl
  

The flooding in New Orleans brought the hazard of contaminated water to the headlines. The floodwaters were described on the news as a "toxic stew". Once water service was restored in parts of the city, residents were cautioned for weeks not to drink tap water. Why all the concern? How long will the threat from contaminated water last?

The first concern is the spread of disease. The microbes that cause disease are called pathogens. Pathogens are virus, bacteria or parasites that come from people who are sick. When they are outside of a body, pathogens must find another body to infect to live and reproduce. Pathogens present in human waste that contaminate water can infect another person through skin contact, a wound, inhalation and ingestion through drinking water or eating contaminated food.

Pathogens and disease
People exposed to pathogens found in contaminated water develop diarrhea and other gastrointestinal illness. Rashes, ear infections and other serious illness like hepatitis are spread through contaminated water. 

So just how long does the water stay contaminated? Well, it depends. It depends on the microbe and the environment. It is important to remember that pathogens need to live and will reproduce inside of a host - they do not grow and thrive outside the body.

In fact, the environment is very hostile to most pathogens and they quickly die.

• Pathogens die-off more quickly in warm water than in cold water. In fact, boiling water is one way to disinfect it.

• Pathogens are killed by ultraviolet light from sunshine.

• Pathogens die off when exposed to high and low pH. Putting lime in the outhouse to raise pH has always been effective at both reducing odor and killing pathogens.

• Pathogens die-off with time. Most pathogens die within a few days to weeks outside the body. Be cautious, however, some viral pathogens like hepatitis live for months outside the body.

Pathogens in groundwater
These considerations become very important when managing well water contamination. Groundwater is cold, not exposed to sunlight and is near neutral in pH. Pathogens die-off especially slowly in contaminated groundwater.

To learn more about water testing, drinking water treatment and water supply protection check the web site for the Soil Environment Technology Learning Lab: http://setll.osu.edu

Karen Mancl, Professor and Extension Water Quality Specialist, can be reached at 614-292-4505, or mancl.1@osu.edu

This column is provided by the OSU Department of Food, Agricultural, and Biological Engineering.