The Pennsylvania Department of Environmental Protection has initiated testing of several Philadelphia area water treatment facilities after test results from April 2011 indicated high levels of one of the radioactive isotopes of iodine, I-131.

Those early test results showed that the Queen Lane water treatment facility registered 2.2 picocuries of I-131, the highest of all 69 sites the Environmental Protection Agency tested throughout the country. The EPA's limit of acceptable I-131 is 3 picocuries, which is significantly lower than other countries. 

I-131 is a byproduct of nuclear fission, and Japan did see an increase of I-131 following the Fukushima disaster. However, the half-life of I-131 (the amount of time it takes before the material is half as potent) is eight days, which should have made detection at the time of the first test impossible.

According to Deborah Fries, a spokesperson for the DEP, researchers are now looking toward cancer patients as a potential cause of the increase in iodine.

"With the half life of 131 being 8 days, the influence of Fukushima would be undetectable," Fries said. "What was found in the source water in the Wissahickon Creek, at this point, having ruled out licensed facilities, we're focusing on patients who receive radiation treatment for cancer."

The reason the department is focusing on cancer patients is due to one specific treatment for thyroid cancer, which involves the use of I-131. Thyroid cells absorb iodine, whether it be radioactive or not, though the radioactive iodine will destroy the cells it inhabits. Patients suffering from thyroid cancer are often given radioactive iodine in hopes that it will dissolve the tumor. Fries, herself a thyroid cancer survivor, noted that since the treatment's inception, more patients are receiving treatment on an outpatient basis. 

"People go home and excrete the isotope for a few days," Fries said, adding that effluence of inpatients at hospitals may have been held for several days before being released, which would indicate why levels of I-131 were not seen before. 

To better understand the causes of the radioactive iodine, the DEP, the Philadelphia Water Department and the EPA are working together to figure out where the iodine is coming from. In April, Spring rain caused the rivers to swell, so to get a more accurate figure, department officials waited for "low flow" conditions, which occurred after the past heat wave. 

"We'll look at what that tells us about what we saw in April," Fries said. "I don't know that we have the sense that that could be prevented."

As soon as the test results come in, Fries says the department's action will become clearer.

"At this point three agencies are working together to understand what the detection of I-131 means," Fries said.