Although farmers work with agricultural chemicals, they probably share the same misconceptions about pesticides as the general public holds.
Donna Houghton, who works for chemical maker Syngenta in Guelph, Ont., outlined some of those mistaken beliefs to the Women’s Fall Focus conference held in Camrose, Alta., last month.
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Well-being improvement can pay off for farmsInvesting in wellness programs in a tight labour market can help farms recruit and retain employees A story on page 82 of the Dec. 6 issue contained chemical toxicity values, called LD50s, for nicotine, caffeine, salt and Axial herbicide. The values listed were for animals, not humans as mentioned. As well, scientists do not multiply LD50s by 100 or 1,000 to get rates applicable to humans. In determining human risk assessments, scientists apply reduction factors of 100 to 1,000 to the dose level at which no health effects were detected in test animals. |
In an interview, she said a common misconception is that naturally occurring chemicals are safer than man-made ones.
Houghton said many people lack scientific education and so they make emotional conclusions that aren’t always right.
“Everything around us is chemical. The dose makes the poison.”
She said all chemicals are made from the same basic building blocks. It is the amount ingested that makes them harmful. She noted that a U.S. woman died last year in a radio station contest when she drank too much water. People think vitamins are good but they can poison themselves if they take too many. Even botulism, one of most toxic substances, is all right in small does, such as when people inject it as botox to remove wrinkles.
Chemical makers must test at what level their products are poisonous. They use lab animals to uncover the lethal dosage, or LD50, which is the point at which half of the test animals die when given an amount of the product, measured in milligrams per kilogram of body weight. The results are multiplied by a factor of 100 to get rates for adult humans and 1,000 for children.
The higher the LD50 number, the less toxic the chemical is because more is needed to cause death. For example, Houghton said the LD50 for humans is 250 mg per kg of nicotine, 350 for caffeine, 3,000 for salt and 3,129 for Syngenta’s Axial herbicide.
Another concept that people don’t think through is risk assessment. Smoking is the worst risk a person can take but other top risky behaviours include driving, drinking alcohol, being overweight and not using sunscreen. Houghton said applying chemicals is lower down the risk level, citing a study carried in Scientific American.
She said people fear flying but their chances of dying in a motor vehicle accident are much higher. Risks rise when the activity is done more frequently.
While chemical formulations tend to be less toxic now than 40 years ago, Houghton said farmers who mix or spray chemicals can reduce their risks if they follow the label, wear protective clothing and use common sense.
Even organic farmers use insecticides derived from chrysanthemums or bacillus thuringensis. As well, the organic practice of using animal manure for fertilizer can be hazardous if it leaves bacteria on the food.
Another public concern with ag chemicals is that they cause higher rates of cancer. Houghton said while some studies have suggested such linkages, their scientific quality can be questionable. She said the best studies have found “no convincing association between pesticides and cancer.”
She said the apparent higher rate of some cancers is a product of an aging population. The body’s ability to make a true cell copy becomes less sharp and mutations can arise after decades of DNA replication.
