Testing For Toxicity

| 10/2/2013 10:25:00 AM

thistleA few years ago, our Landowners Association was obsessed with eradicating all thistle plants and were using 2,4,D Amine 4 as their herbicide of choice. As I was driving down the road one day the wind drift from the spraying operations came through the open window and hit me in the face. It triggered an instant asthma attack and caused seriously burning eyes. Since the personnel in charge refused to divulge what was being applied or how it was being used I had to go through the enforcement branch of the Colorado Department of Agriculture and EPA to make this determination.

While waiting for this information, I had done some extensive research on herbicides which proved to be very informative. One of my areas researched was how tests were accomplished for toxins. This took me to a EPA web page that explained the EPA testing procedures. Fortunately I made a copy of the page as I have not been able to relocate it since. 

What I learned was there were considerable limitations involved in the testing process. Human toxicity data did not exist for many chemicals therefore making it difficult to draw any conclusions. Tests on laboratory animals was available with the EPA which required a minimum set of studies for toxicity prior to approval. These tests, however, do not always accurately reflect the full potential hazard of toxins. Humans are not the same as rats, rabbits or dogs. Rats have a much higher tolerance to many toxins and are able to deal with them without suffering the same side effects humans do.

The EPA requires testing two species of animals to achieve a tolerance factor. Humans have different susceptibilities to toxins which differs between individuals. The testing process therefore does not represent the full risk factor humans may experience. Rats are able to process and eliminate some toxins where humans are not always able to do the same. 

Children and developing fetus are far more susceptible to toxins than adults who have more developed immune systems. In laboratory tests the lab animals are only subjected to one chemical where in the environment we humans are subjected to multiple chemical exposures simultaneously. The testing is usually for a limited duration where in the environment we are subjected to the same toxins over a much longer duration and repeatedly. Not all toxicity is studied in detail nor for a sufficient duration to make sure what the potential human hazard actually is. Once a chemical or component has been approved the burden of proof changes and if human dangers are identified in the future the battle is an up hill one for contesting the product which is already in production and on the market.

I read numerous independent reports where risk factors have been subsequently identified and the chemical industry counters with contrary reports. A prime example is the herbicide Round Up and other very similar products which although known to have significant human toxicity dangers remain on shelves and has not been reclassified. Often the priority for any study of toxins for carcinogens, reproductive toxins etc, are as much political as scientific . It is the chemical manufacturer that actually performs the testing process. The EPA does include a weight factor for many chemicals such as the impact on children but this risk factor is subjective using a 1-10 value. It is supposed to be a built in safety factor but as stated is more subjective than objective. 

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