Saturday, June 16, 2007

Quick: Unintended consequences

For some reason, I like reading about unintended consequences. It seems that reality always has more depth and complexity than we would like to admit. This is part of the reason why people who claim to have the answers, generally don't.

This comes to mind because I was just reading a little about the effects of pesticides on plants:
Pesticide residues in plants are regulated to protect human health. They are measured when plants enter the market. However, this procedure does not consider that pesticides modulate secondary metabolism in plants when they are applied. The question arises whether it is conceivable that pesticide-induced changes in the chemical composition of plants influence human health. The examples resveratrol, flavonoids, and furanocoumarins indicate that plant phenolics may have subtle effects on physiologic processes that are relevant to human health. These effects may be beneficial, e.g., due to the inhibition of the oxidation of macromolecules and platelet aggregation or by their pharmacologic properties. Depending on concentration and specific chemical composition, however, plant phenolics may also be toxic, mutagenic, or cancerogenic. The consequences of a modulation of plant phenolics on human health are complex and cannot be predicted with certainty. It may be that the modulation of plant phenolics at the time of application and not the usually low level of pesticide residues at the time of consumption is critical for human health.

Put another way, pesticides can actually alter the nutritional properties of plants by removing environmental stress, stress which would have caused the plants to produce nutrients that may be important to humans. I hadn't considered that.


Nivi said...

Cool. There is a field called "System Dynamics" that studies these feedback loops.

Another example is that creating new roads increases traffic congestion instead of decreasing it.

Jay Forrester and John Sterman are a couple of the big shots in this field if you want to look into it.

Manoj said...

Reminds me of my eighth grade teacher's talk on biomagnification!!!!

halsn said...

Consider also that endogenous pesticides are likely more dangerous than well-tested pesticides that you can wash off:

"Plants in the human diet contain thousands of natural “pesticides” produced by plants to protect themselves from in­sects and other predators: 72 have been tested and 38 have been found to give cancer to rodents. Thus, exposure to synthetic rodent carcinogens is small compared to the natural background of rodent carcinogens."

For example watch out for "organic" celery, bred to look good without pesticides:

"The disease-resistant, high-quality brand of celery carried by these stores had higher levels of furanocoumarins, potent photosensitizers and a known cause of phytophotodermatitis, than other brands (p = 0.01). A randomly selected nationwide sample of stores in this chain showed dermatitis in 13 of 17 states and 26% of produce workers surveyed. Plant breeding to produce a more disease-resistant celery stock may lead to increased levels of endogenous furanocoumarins, resulting in phytophotodermatitis in grocery workers."

Unknown said...

"...reality always has more depth and complexity than we would like to admit." Yes! I think you might enjoy reading comp.risks: I've been reading this for years, and there are many wonderful stories of unintended consequences there. Very humbling.