Farm and Field

Pesticide exposure linked to poor sense of smell

Posted: Mar. 9, 2019 12:01 am Updated: Mar. 11, 2019 3:10 pm

A Michigan State University study is the first to show an association between unusually high pesticide exposure and poor sense of smell among aging farmers.

As the start of the study, which examined more than 11,200 farmers over a 20-year period, about 16 percent of participants reported having experienced a high pesticide exposure event, or HPEE, such as a large amount of pesticide spilling on their body. Two decades later, they were asked if they suffered olfactory impairment, or a partial to complete loss of sense of smell. Farmers who reported an HPEE were 50 percent more likely to report a poor sense of smell at the end of the study.

The research showed that an immediate washing with soap and water might mitigate risk. Compared to farmers who never experienced a high exposure event, those who did and washed within three hours had about a 40 percent higher risk of having problems with smell. Those who waited four or more hours saw their risk potentially double.

The study, a collaboration with researchers from the National Institute of Environmental Health Sciences and the National Cancer Institute, was published in the journal Environmental Health Perspectives.

"Studying farmers give us more reliable data on pesticide exposures than if we had studied the general population," said Honglei Chen, lead author and professor epidemiology. "Because they use pesticides more and it's part of their job, they're more likely to remember what pesticides they used, and in cases of high exposures, report the specific events."

In the study, Chen was able to identify two insecticides, DDT and lindane, as well as four weed killers -- alachlor, metolachlor, 2,4-D and pendimethalin -- that showed a greater association with poor sense of smell.

"Farmers reporting incidents involving unusually high exposures to certain organochlorine insecticides, such as DDT and herbicides including 2,4-D, were more likely to have a poor sense of smell," he said. "More research needs to be done, but some studies have linked these chemicals to Parkinson's and possibly dementia, too."

Cow deaths

On top of dealing with harsh winter weather in feeding cows, cattle farmers must guard against too much nitrate in poor-quality hay.

High nitrate, mostly concentrated in grass stems, causes quick death, said Tim Evans, head toxicologist at the University of Missouri Veterinary Medical Diagnostic Laboratory. Nitrate converts to nitrite in a cow's rumen. Nitrite in the blood blocks oxygen update, and without oxygen, cows die quickly.

"Testing low-quality forage for nitrate is urgent," Evans said. "Producers need to know potential problems."

MU Extension beef nutritionist Eric Bailey said supplements dilute nitrate in cow diets. Adding starchy grain speeds up rumen fermentation more than other feeds.

"I'd start with half a pound of grain per 100 pounds of body weight. In short order, that goes to a pound of grain per hundredweight as rumens adapt to more grain," Bailey said. Shortages of hay and grass followed droughts starting in 2017 through the summer of 2018, and "many farmers feed hay they wouldn't normally feed," Evans said.

Nitrate distribution isn't uniform through forages.

"In one case, with 14 dead cows, a farmer sent four hay samples," Evans said. "Two samples had no nitrate, one had moderate nitrate, while the fourth had toxic levels over 1 percent nitrate."