That could change, based on the findings of a new study published in the Annals of Allergy, Asthma and Immunology. The authors found that a breakdown by-product of a pesticide used on genetically modified crops, lawns and golf courses, and of chlorine-treated drinking water, was associated with higher rates of food allergies.
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The authors used data collected from 2,548 people who had been tested for specific environmental and food allergies and for levels of these breakdown by-products, called dichlorophenols. Based on their analysis, the higher the levels of dichlorophenols in a person's urine, the more likely that person was to have an allergy to milk, eggs, peanuts, or shrimp. They didn't find the same relationship to environmental allergens, such as dogs, cats, ragweed, or grass.
Because the study simply found a relationship between the chemicals and food allergies, she says, it's difficult to say if one causes the other. But she says her results play into the "hygiene hypothesis" that we're scrubbing ourselves clean of good bacteria and, in doing so, are weakening our immune systems' ability to protect us against foreign substances.
Dichlorophenols have been found to kill bacteria, says lead author Elina Jerschow, MD, MSc, assistant professor in clinical research at Albert Einstein College of Medicine in New York, "and it's been found that anything that decreases the bacterial load in our environment is associated with more allergies."
Dichlorophenols are breakdown by-products of chemicals that contain chlorine. One of the biggest sources of those chlorinated chemicals in our environment is the herbicide 2,4-D, the second most widely used herbicide in the U.S., which degrades into 2,4-dichlorophenol in soil and water. It's one of the most commonly used lawn weed killers on the market today, but it's also used as an herbicide on wheat and it's frequently sprayed on farms between rows of asparagus, apples, peaches, almonds, pears, strawberries, cherries, cranberries and potatoes.
Dichlorophenols are also breakdown by-products of the chlorine compounds used to disinfect tap water, which is currently one of your major exposure sources. They can infiltrate your home's indoor air through mothballs and room deodorizers as well, both of which contain a compound called dichlorobenzene, and through chlorine bleach or other cleaning products that contain chlorine. "As long as you have chlorine in your environment, you might get exposure to these chemicals," says Dr. Jerschow.
What's more concerning is that the U.S. Department of Agriculture (USDA) is on the verge of making a decision that could expose Americans to extremely high levels of dichlorophenols in our food supply. The agency is expected to approve a new variety of genetically modified corn bred specifically to resist 2,4-D within the next few months and a 2,4-D-resistant soy not long after that. Those crops directly convert 2,4-D into 2,4-dichlorophenol, one of the dichlorophenols associated with food allergies in this study, and that would increase the public's exposure to the chemicals through food, says Bill Frees of the nonprofit Center for Food Safety. That group estimates that the approvals of both crops would increase the use of this potent herbicide from 27 million pounds a year to more than 100 million pounds.
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What You Can Do
It might be difficult to eliminate all exposures to chlorine breakdown products in your home, but here are a few ways you can cut down on what's getting into your system:
• Demand organic. Not only will you be limiting your exposure to chlorinated pesticide residues, but you'll also be supporting farmers who don't plant genetically modified crops, which are banned under organic standards.
• Ban the bottle. It's hard to say whether typical household water filters will remove dichlorophenols from tap water, says Dr. Jerschow, because they dissolve so well in water. But don't assume that bottled water is any safer, she cautions. Roughly 50 percent of bottled waters on the market are simply filtered tap, so they too could contain dichlorophenols. A standard household filter will remove chlorine, and that will prevent chlorine breakdown products in your indoor air.
• Make your own cleaners. Rather than resorting to chlorinated commercial cleaners, make your own with white vinegar, which Consumer Reports recently declared was The Best Cleaner Ever. Need some ideas? Check out these Homemade Cleaners that Really Work.