Jan 29 2012
Determining the dose and other factors affecting toxicity
Thursday and Friday, we watched a video and discussed reasons children are likely to be more vulnerable than adults to the effects of environmental toxins:
1. Age/developmental stage. Children don’t just pop out of the womb with fully developed detox organs (liver, kidneys, lungs) or immune systems, so they may react differently to a toxin than an adult.
2. “Living low” and oral habits. Very young kids (esp. those that haven’t learned to walk yet) spend a lot of time on the floor crawling, and can transfer trace toxins from hand to mouth often since that’s how they explore the world.
3. Pound for pound, they take in more of a toxin than adults do. If a 20 lb. child takes in 1 ounce of a toxin, then he receives a higher does than a 200 lb. man taking in the same amount. Make sense?
If you missed the video, I don’t have a full digital version but you can get some tidbits at this EPA page under the link:
Chemicals – “NOW with Bill Moyers: Kids and Chemicals.”
On Friday we were discussing other factors mentioned in the video (and text) that may impact toxicity, like the timing of the dose, the persistence of the chemical, the solubility of the chemical (could lead to bioaccumulation/biomagnification), and any synergistic effects. Combined with the list above, we have quite a number of things that affect the toxicity of a chemical besides the dose. Regardless, the dose is the most common measure of toxicity, and that is done by conducting a LD50 dose-response study. The LD50 is also known as the median lethal dose.
We will do our own crude LD50 test to understand the process better. If you want to know more, more, more, here is a link to a great Environmental Contaminants and Toxicology Reader at The Encyclopedia of the Earth web site. We’ve only scratched the surface, and this will give you a much more complete picture of toxicology studies and principles. Maybe a great review site before the AP Exam.