Time to test assumptions about health effects that guide risk assessment: toxicologist

Governments and the nuclear industry have failed to address serious data gaps and untested assumptions guiding exposure limits to Cesium (Cs)-137 released in the Chernobyl accident in 1986 and this year's incident at Fukushima, says University of Massachusetts Amherst toxicologist Edward Calabrese. It's time now to move toward adopting more evidence-based risk assessment for the future, he adds.

"It is also critical that the linear, no-threshold (LNT) model and the alternative models, such as the threshold and hormesis models, be objectively assessed so that society can be guided by scientific data and validated models rather than ideological perspectives that stealthily infected the process for and ," he states.

Calabrese's commentary, "Improving the scientific foundations for estimating health risks from the incident," is included in this week's special issue of devoted to documenting the estimated release magnitude and distribution of Cs-137 from the nuclear incident in Japan after the March earthquake and tsunami.

After his career-long study of hormesis persuaded Calabrese that low doses of some chemicals and radiation are benign to humans or even helpful, he says a "comprehensive reappraisal" of the LNT model for cancer risk assessment is urgently needed. He argues that the LNT model was incorporated into U.S. regulatory policy in the 1950s based on faulty assumptions and even manipulation of the scientific literature. Its use has become codified in regulatory agencies despite its "questionable scientific foundations," he says.

In addition to over-reliance on the LNT, Calabrese contends, regulators also place too much weight on assumptions about the ingestion of contaminants in soil by children, in particular dioxin, which date from the 1980s at Times Beach, Mo. "Subsequent soil ingestion studies in children would prove this default exposure assumption represented a massive overestimation, being too high by 200-fold," he points out. Without follow-up studies to provide more accurate data, "costs of clean up at Times Beach alone would have been many billions of dollars more," he adds, illustrating that non-validated assumptions can markedly affect the risk assessment outcome.

Calabrese also criticizes expert advisory groups and government agencies for rendering exposure guidance "based on hypothetical risks of Cs-137" and using highly precise estimates that give "a false impression of considerable accuracy." In fact, he says, acceptable levels of Cs-137 exposure in Japan are more than three times higher than levels permitted in the Ukraine, while both are probably based on "little independent analysis."

Overall, precautionary urges that pressure regulators to rely on the most conservative option have a downside, in Calabrese's opinion. They lead to multiplicative protective factors that can add substantially to remediation costs "without validated assurances of accompanying benefit."

Lower is not always better when it comes to enhancing public health, he says. "It is time for the responsible governmental and industrial organizations to develop a practical plan to fill important data gaps."

Provided by University of Massachusetts at Amherst

not rated yet

Related Stories

New Study Challenges How Regulators Determine Risk

Dec 26, 2006

A new study of a large U.S. National Cancer Institute database provides the strongest evidence yet that a key portion of the traditional dose-response model used in drug testing and risk assessment for toxins is wrong when ...

Japan disaster not similar to Chernobyl: officials

May 17, 2011

The potential health consequences of the nuclear crisis at Japan's Fukushima Daiichi plant are not equal to those caused by the disaster at Chernobyl, Japanese health officials said Tuesday

Mountains limited spread of fallout from Fukushima

Nov 14, 2011

A map of radioactive contamination across Japan from the Fukushima power plant disaster confirms high levels in eastern and northeastern areas but finds much lower levels in the western part of the country, thanks to mountain ...

Recommended for you

Study reveals state of crisis in Canadian foster care system

18 hours ago

A new study of foster care in Canada led by a researcher at Western University reveals a shrinking number of foster care providers are available across the country to care for a growing number of children with increasingly ...

Researchers prove the benefits of persimmons for diet

20 hours ago

Alba Mir and Ana Domingo, researchers from the Department of Analytical Chemistry of the University of Valencia, under the supervision of professors Miguel de la Guardia and Maria Luisa Cervera, from the same department, ...

Hand blenders used for cooking can emit persistent chemicals

20 hours ago

Eight out of twelve tested models of hand blenders are leaking chlorinated paraffins when used according to the suppliers' instructions. This is revealed in a report from Stockholm University where researchers analyzed a ...

User comments