THRESHOLD VERSUS NON-THRESHOLD CARCINOGENS

"A non-threshold carcinogen is usually genotoxic and is presumed to have no safe dose. A threshold model is based on the assumption that developing cancer requires a minimum level of exposure (the threshold), below which no cancer will develop."

In 2006 the U.S. EPA asked the National Research Council (NRC), part of the National Academy of Sciences (NAS), to review the 2003 version of the U.S. EPA assessment of the health effects of TCDD and related compounds. While they agreed with the EPA's findings on a number of matters they did however find "...that the EPA's decision to use only the non-threshold model for extrapolation was not adequately supported and recommended that U.S. EPA use both threshold and non-threshold models to extrapolate risks at lower levels.".

There have been studies and assessments by Health Canada, the Canadian Council of Ministers of the Environment (CCME) and numerous other studies by individual scientists over the decades. Most of the results have been supportive while some studies have been less supportive of particular findings. For example some studies show a clear association of TCDD with diabetes, others less so. One study strongly stated that their review indicated that "...results were consistent for an association with defective brain development in infants.". Also some studies believe that there is a strong association between ischemic heart disease and TCDD and a weaker association between TCDD and all cardiovascular disease.

The loopholes for both government and industry to avoid accountability for their culpabilty in the pain, sufferring and death of hundreds of thousands to millions of Canadians are immense. These studies are at the population level not the level of the individual. Therefore for an individual to sue for damages for the pain and sufferring or loss of a loved one, especially in Canadian courts, is almost hopeless. An example would be an individual exposed by highway spraying by the Ontario Ministry of Transport through the 50s, 60s and 70s. To find out for example half way through the trial that the individual involved also was exposed to TCDD by a parent living beside Uniroyal Chemical in the 40s and 50s would be a confounding variable. Which exposure (or both) did the damage?

Again while I am still reading this report by the Fact-Finding Panel, to date I find it very disturbing. The Panel have indeed found evidence of gross negligence by our political authorities while carefully not using those words or terminology. They have indicated the current scientific understanding regarding TCDD (especially 2,3,7,8 TCDD) and it is horrific. Again their language is much more nuetral and put in medically correct terms. My confidence in the basic commonsense and integrity of our political leaders past and present continues to plummet.