An unidentified worker at Freedom Industries shovels NAPA premium oil absorbent onto the ground, on Jan. 10, 2014 in Charleston, West Virginia. Tom Hindman/Getty Images

Things may be returning to normal for thousands of West Virginia customers of American Water, which had its water supply contaminated by a chemical spill last week, but tens of thousands are still without fresh water, and many of those who’ve been told their water is OK to drink remain skeptical.

A week after a tank at a chemical storage site owned by Freedom Industries leaked thousands of gallons of 4-methylcyclohexane-methanol, or MCHM, into the Elk River, contaminating the drinking water of 300,000 West Virginia residents, some say they do not trust the insistence of the Environmental Protection Agency and the West Virginia Department of Environmental Protection that water from the river is becoming safe to drink.

Over 200,000 people are still under a “do not drink” order, but even those who have been told their water is OK are concerned about its health effects.

After getting the all-clear from American Water, Kanawha City resident Shane Casdorph jumped into the shower, but shortly afterward began to feel itchy.

"My ears were burning," Casdorph told the Charleston Gazette. "I've got red places on my feet and back and a red rash on my back."

Kanawha-Charleston Health Department officer Rahul Gupta told the Gazette that at least 100 people had entered the emergency room since the "do not drink" order was lifted. They complained of eye irritation, stomach pain, vomiting and diarrhea.

But Gupta insisted the water was still safe to drink.

Little is known about MCHM, which is used to process coal before it is burned. The EPA has claimed that water containing less than 1 part per million (ppm) of the chemical is safe to drink, but some experts question how that safety threshold was determined.

Richard Denison, a scientist with the Environmental Defense Fund, told The New York Times that the EPA’s calculation seemed to be based on one unpublished study.

“This is a significant departure from how the EPA normally calculates risk,” he said.

When asked about the 1 ppm designation, American Water referred the Charleston Gazette to the Centers for Disease Control and Prevention, but the CDC referred the Gazette back to American Water.