As expected, per my article in The Houston Chronicle on 9/4/17, tests of flood water from Hurricane Harvey are suggesting that the water is not clean, probably due to contamination by human waste and water treatment facilities. This water cannot be ingested without medical risk unless treated first by mechanical filtration of particulate matter and then boiled and/or treated with sterilization chemicals, such as iodine or chlorine.
Specifically, high levels of Escherichia coli (E. coli) bacteria have been found, as well as excessive lead and arsenic content. Unless there is direct substantial ingestion of lead or arsenic, these elements should not pose a risk of toxicity. Lead and arsenic poisoning result in illness by cumulative exposure over time, and so would unlikely account for symptoms or illness acutely. Further contaminants may yet be found.
E. coli and other bacteria are a risk for diarrheal illness (and possibly systemic sickness with fever) if ingested. Otherwise, such bacteria are not worrisome unless they have a portal of entry into the body, such as through disrupted skin- broken down skin barrier from rashes, chronic skin disorders, or wounds.

So, proper actions with flood water contact that had contaminated surfaces are,
1. Update tetanus immunization if at least 10 years since last vaccination; or if there is an unclean, inflamed, or devitalized tissue wound.
2. Wear protective footwear with thick soles, always.
3. Be sure to clean the insides of footwear, especially boots, with decontaminating solution (such as 1:10 Clorox to water dilution), especially after wearing in such water.
4. See a physician promptly for any wounds developing worrisome changes (discharge, significant discoloration or pain, blisters, extending inflammatory changes into surrounding tissues, or if accompanied by fever or general illness.
5. See a physician for diarrheal illness.
6. See a physician for new onset of systemic illness: fever, chills, poor appetite, weakness, nausea/vomiting, abdominal pain.

Edward R. Rensimer, MD
Director, International Medicine Center

Link to the New York Times article A Sea of Health and Environmental Hazards in Houston’s Floodwaters for more information.