CEDAR FALLS - A research article published by a pair of University of Northern Iowa professors concludes the link between mercury and autism can't be ruled out and needs further study.

The results don't prove mercury exposure causes autism, a developmental disability that can affect language and social skills.

Autism's prevalence has burgeoned in the last two decades, and is estimated to affect one in 150 children in the country.

The article drew both quick rebukes and enthusiastic praise from those debating the link between mercury in vaccines and autism.

But Catherine DeSoto and Robert Hitlan, both psychology professors, said their work doesn't directly address the controversial issue because mercury exposure can occur in more than one way.

"This study doesn't prove that vaccines cause autism," DeSoto said. "It does suggest that ruling out mercury as playing any role in autism might have been a bit premature."

The results, published in the Journal of Child Neurology in November, created a stir because it is based on the only case-controlled study to examine the relationship of mercury blood levels and autism.

The findings caught the attention of Gov. Chet Culver, who met with DeSoto late last year while visiting UNI on unrelated business. Culver was collecting information on the environmental effects of coal power plants, not the vaccine-to-autism link, DeSoto said.

Rep. Dan Burton, R-Ind., submitted the article as evidence to judges presiding over a federal vaccine court charged with deciding if families injured by vaccines should be compensated.

Typical public criticism, DeSoto said, read like an anonymous blog comment written shortly after the paper was published: "DeSoto and Hitlan are a bad joke, in my opinion."

But an online aggregator of academic articles, Faculty of 1000 Biology (at www.f1000biology.com), took notice and flagged the article as a "must read."

"I found this article oddly exciting and disturbing because it involved the re-analysis of a classic paper used to debunk the mercury hypothesis of autism spectrum disorder and the original conclusion is now in doubt," read the review on the site. "It certainly will re-ignite a controversy where, alas, there is more heat than light."

The UNI professors did not conduct the field research. They re-examined data from a 2004 article published in the same journal, co-authored by Virginia Wong, a child neurologist and professor at University of Hong Kong,

The original article studied the mercury levels in the blood and hair of 82 children with autism and 55 children without the disorder, and found no relationship between high mercury levels and autism.

The results were cited by at least 21 articles, and was referenced in a 2006 report to the Texas legislature on the economic impact of implementing pollution controls on the state's power plants.

However, the original study contained several errors, ranging from mistakes in reporting statistical findings to incorrectly listing the age range of the children studied.

When the UNI professors and the original authors re-crunched the numbers using the primary data, they both concluded the original results severely understated the relationship between mercury and autism.

DeSoto and Hitlan used their own analysis, which found a statistically significant relationship.

However, reanalysis by Wong, one of the original authors, came up with results just above the accepted threshold when results are considered statistically significant - an outcome duplicated by DeSoto and Hitlan.

However, their interpretation of Wong's outcome differed: DeSoto and Hitlan wrote the results were statistically significant enough that the link should be further studied. The original authors, writing a correction in the journal, maintained the conclusion they came to with the original, flawed, study: High mercury blood levels don't cause autism.

But in an interview, Wong said she doesn't dismiss the link between mercury and autism.

"I totally agree (with DeSoto and Hitlan). We need to repeat this study," she said.

Vaccine controversy

Some parents firmly believe Thimeresol, a preservative used in vaccinations which contains ethyl mercury, triggered a sharp increase in autism in the early 1990s. Many in the medical community are equally adamant that no evidence exists to support the claim.

Autism rates continue to rise even though all but trace amounts of mercury were dropped from childhood vaccines in 2001.

A study widely publicized last month found mercury in vaccines cleared from the body at least 10 times faster than previously believed. The finding punched another hole in the theory that the preservative causes autism.

However, flu shots still contain Thimerosol. Earlier this month, activists lobbied the Iowa legislature to remove the preservative from the vaccinations.

And again, tempers flared as exasperated medical professionals repeated a familiar line to equally frustrated parents.

"It's been like five years since we took (Thimerosol) out," state epidemiologist Dr. Patricia Quinlisk told the Associated Press. "But they don't like you talking about that because if it's been out of the vaccine for that many years, autism rates ought to be going down if it was a cause. And it's not. It's going up."


Comment: Except, if you do the proper statistical analysis and include all neurodevelopmental disorders, the rates have been dropping since the removal.


While childhood vaccines have received the most attention, fish consumption remains the most common way that people are exposed to mercury. Globally, the single largest source of mercury emissions - which often travel around the world - are power plants burning fossil fuels, particularly those in Africa and Asia.

Contact Jens Manuel Krogstad at (319) 291-1580 or jens.krogstad@wcfcourier.com.