Pesticides + Poison Gases = Cheap, Year-Round Strawberries

By Bill Walker, Investigations Editor, and Sonya Lunder, Senior Analyst

Americans eat nearly eight pounds of fresh strawberries a year - and with them, dozens of pesticides, including chemicals that have been linked to cancer and reproductive damage, or that are banned in Europe.

Strawberries tested by scientists at the U.S. Department of Agriculture in 2014 and 2015 contained an average of 7.7 different pesticides per sample, compared to 2.3 pesticides per sample for all other produce, according to a new EWG analysis.

What’s worse, strawberry growers use jaw-dropping volumes of poisonous gases – some developed for chemical warfare but now banned by the Geneva Conventions – to sterilize their fields before planting, killing every pest, weed and other living thing in the soil.

For these reasons, strawberries are again on the top of the Dirty Dozen™ list for 2017. USDA tests found that strawberries were the fresh produce items most likely to be contaminated with pesticide residues, even after they are picked, rinsed in the field and washed before eating.

If you want to avoid pesticides and don't want strawberries grown in soil injected with nerve gases, EWG advises that you always buy organically grown berries. We make the same recommendation for other Dirty Dozen™ foods.

The facts about strawberries and pesticides come from the USDA’s Pesticide Data Program.  In 2014 and 2015, USDA scientists tested 841 batches of strawberries - about 88 percent of which were grown in the U.S., with the rest coming from Mexico.

The USDA’s 2014 and 2015 strawberry tests found that:

  • Almost all samples – 99 percent – had detectable residues of at least one pesticide.
  • Some 29 percent had residues of 10 or more pesticides.
  • The dirtiest strawberry sample had residues of 21 different pesticides and breakdown products.
  • Strawberry growers used 74 different pesticides in various combinations.

How hazardous are the chemicals used on strawberries?  Some are fairly benign. But some are linked to cancer, reproductive and developmental damage, hormone disruption and neurological problems. Among the worst:

  • Carbendazim, a hormone-disrupting fungicide that damages the male reproductive system, was detected on 20 percent of 2014 and 2015 samples. The European Union has banned it because of its intense toxicity.
  • Bifenthrin, found on more than 33 percent of samples in 2014 and 2015, is an insecticide that California regulators have designated a possible human carcinogen.
  • Malathion, found on 11 percent of recent samples, is toxic to the nervous system and, according to the International Agency for Cancer Research, is a probable human carcinogen. It is often sprayed to eradicate mosquitos and other insects.

As disturbing as these results are, they do not violate weak U.S. laws and regulations on pesticides in food.

Only about 6.3 percent of the strawberries sampled in 2014 and 2015 had levels of pesticide residues considered illegal. Of these samples, 30 had pesticide levels that exceeded the "tolerance level," or legally permissible level set by the Environmental Protection Agency. Twenty-six samples contained pesticides illegal for use on strawberries.

The EPA’s tolerance levels are too lenient to protect public health. They are a yardstick to help the agency’s personnel determine whether farmers are applying pesticides properly. The levels were set years ago and do not account for newer research showing that toxic chemicals can be harmful at very small doses, particularly when people are exposed to combinations of chemicals.

If pesticide tolerance levels were set to protect the health of children, who are more vulnerable than adults to small doses, more fruits and vegetables would fail EPA standards. The current EPA pesticide tolerances are like having a 500 mph speed limit – if the rules of the road are so loose it’s impossible to violate them, no one can feel safe.

Fresh strawberries were once a seasonal treat, available in limited supply only for a few spring and summer months. In recent decades, the increased use of pesticides and other chemically aided growing methods have made cheap strawberries available all year, and aggressive marketing campaigns have spurred consumption. Today the average American eats nearly four times as many fresh strawberries per year as in 1980.

More than three-fourths of the fresh strawberries sold in the U.S. are grown in California, the state that most carefully tracks pesticide use. California data show that in 2014, nearly 300 pounds of pesticides were applied to each acre of strawberries – an astonishing amount, compared to about five pounds of pesticides per acre of corn, which is considered a pesticide-intensive crop.  

But only about 20 percent of the chemicals used on California strawberries were pesticides that can leave residues on harvested fruit. The other 80 percent – more than 9.7 million pounds in 2014 – were fumigants, which are poisonous gases injected directly into the ground to sterilize the soil before planting.

Fumigants are acutely toxic gases that kill every living thing in the soil. Some were originally developed as chemical warfare agents, now banned by the Geneva Conventions. After growers inject fumigants, they cover the fields with plastic tarps in an effort to keep the gas underground and away from people and animals. But, fumigants can leak during application and from torn tarps, sending the deadly fumes adrift, and endangering farm workers and people who live nearby.

The most notorious strawberry fumigant is methyl bromide. An international treaty banned it in 1987 because it destroys the earth's protective ozone layer, but for almost 40 years U.S. strawberry growers have fought for so-called “critical use exemptions” from the EPA, and were granted access to decreasing amounts of the chemical over the past several decades. This is the first year that the EPA will not permit any methyl bromide use for strawberries.

Almost two decades ago, EWG and other groups campaigned against methyl bromide in California's Central Coast region, where most of the U.S. crop is grown. Urban development in the region has brought hundreds of thousands of residents into close proximity with strawberry fields. The campaign forced the state to establish protective buffer zones near schools and neighborhoods, and to restrict methyl bromide injection during school hours. These rules reduced Californians’ exposure to methyl bromide but fell far short of eliminating this dangerous chemical.

Under the EPA phase-out, methyl bromide use on strawberries has steadily declined. Today, growers are using less methyl bromide on their strawberry fields. But the newer soil fumigants replacing it are also hazardous. These include chloropicrin, the active ingredient in tear gas, and 1,3-dichloropropene, a carcinogen sold by Dow Chemical Company as Telone. Both are banned in the European Union.

In 2014, the Center for Investigative Reporting revealed how Dow lobbied for and won a loophole to allow California strawberry growers to double their annual use of Telone. As a result, the Center reported, more than a million Californians were regularly exposed to higher concentrations of Telone than were previously considered safe. The same year, a state study found that chloropicrin in the air in Watsonville, a rapidly growing city in the heart of the California strawberry belt, exceeded the state's safety standard by 40 percent.

The organic alternative to fumigation combines the traditional tool of crop rotation, meant to control the buildup of pests and pathogens, with a new technology that’s akin to composting. Growers mix a carbon-rich material such as rice bran or molasses into topsoil, which is then saturated with water and covered with a plastic tarp. Under the tarp, the organic slurry gives off natural byproducts that are toxic to pathogens.

This method works as effectively as fumigation, with growers who use it reporting almost no loss in crop yield. It’s more expensive, driving up the cost of organic strawberries – more than $4 a pound in the store, compared to about $2.50 a pound for the conventional variety. Organic strawberries represent less than 10 percent of the market nationwide, but their share is growing rapidly. As more growers turn away from pesticides and fumigants, the price of organic produce is expected to drop.

For those of us who don’t want to eat pesticide residues and who want to stop fumigants from endangering farm workers and neighbors, buying organic is a small price to pay. The transformation of strawberries from an occasional treat to a cheap and abundant supermarket staple should serve as cautionary tale about the consequences of chemically driven industrial agriculture.

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