Buying organic produce instead of nonorganic means you’ll be reducing your overall exposure to pesticides, but it’s still not known whether exposure to the pesticides currently in use is harmful to your health.

If we were writing about the risk of pesticides decades ago, when DDT and other now-banned pesticides were in use, it would be easy for us to warn you of the dangers of pesticide exposure. When consumed, these older-generation pesticides were stored in body fat, which meant they remained in the body for a long time—and could cause illnesses such as non-Hodgkin’s lymphoma and probably other cancers to which they were linked. But the 900 or so pesticides currently approved for use in the U.S. are designed so they aren’t stored by the body when consumed. Instead, if they are ingested, your body will metabolize the chemicals and then dispose of them quickly. This is not to say the chemicals in pesticides can’t do harm over the course of the few days during which you’ve been exposed to them or that repeated exposures can’t do harm. It’s just that it’s very difficult for scientists to monitor study subjects to evaluate levels of harm because after a few days following consumption, the chemicals disappear. And because pesticides are so ubiquitous and we’re all exposed to trace amounts of so many types by simply going about our lives, it has been very difficult for researchers to isolate the effects from exposure to one type of pesticide.

Even though newer generations of pesticides are likely safer than the old, some of the ingredients in currently used pesticides are scary stuff: among approved pesticides, there are about 20 ingredients that are known to cause cancer in laboratory animals, and are classified as possible human carcinogens. And there is evidence that fetuses and babies exposed to pesticides and other common chemicals used in agriculture may be more susceptible to a wide range of health problems, including attention deficit disorder, asthma, and cancer. So it’s no surprise that most consumers want to limit their exposure to pesticides.

Compared to the scant amount of concrete data on the health risks of pesticides, there is more research that indicates organic produce does contain smaller amounts of pesticides than nonorganic. Although pesticides can’t be used to grow organic produce, it’s not necessarily pesticide-free—if the plants were grown in soil that has pesticide residue in it, then the produce may still contain the pesticide. Organic produce can also be contaminated with pesticides from pesticide drift—chemicals wafting into fields from nearby crops. But comparisons of the presence of pesticides in organic versus nonorganic produce have shown that you are much less likely to be exposed to pesticides if you buy organic. It is estimated about 25 percent of organically grown produce contains pesticides, compared to 75 percent of nonorganically grown. And when pesticides are found in organically grown produce, the amounts are usually far smaller than in their conventional counterparts.

The risk of pesticide exposure is greater with some fruits and vegetables than with others. So one way to decrease sharply your exposure to pesticides without paying premium prices for all the produce you buy is simply to buy organic if the item is highly likely to be laced with pesticides and buy nonorganic if the risk of pesticide exposure is low.

We weren’t able to find any research that indicates organic produce is less likely to contain E. coli or other harmful bacteria compared to nonorganic produce. Outbreaks have been caused by contamination of organic as well as nonorganic crops.

Although it’s unclear whether organic produce is markedly safer for your health than nonorganic, there is overwhelming research on one, related subject: you’re better off eating nonorganic produce and risking possible exposure to pesticides than not eating fruits and vegetables at all. According to the National Cancer Institute and a wide range of studies, those who eat more fruits and vegetables have a much lower risk of having heart disease and cancers of the colon, mouth, esophagus, stomach, and lung.

Meat and Dairy

There is more consensus as to the risks from pesticides and other potential harms to human health when comparing organic and nonorganic meat and dairy products.

Pesticides are rarely found in beef, poultry, eggs, or milk, whether the product is organic or nonorganic. The reason for this is that, as we mentioned above, current generations of pesticides are designed to be metabolized by animals’ bodies quickly and not stored. Even if a steer has been exposed to a pesticide, by the time its meat reaches your plate, that pesticide is highly likely to be long gone. When researchers have found pesticide residue in meat and dairy products, it usually is an older generation substance that was banned years ago, but persists in the environment. This possibility is of course disconcerting, but organic farmers are just as likely to face the problem of contaminated soil as nonorganic farmers are.

As with produce, there’s little evidence that organically raised cattle are less likely to be contaminated with E. coli or other germs. The reason for this is that bacteria can be spread through multiple routes, including water, insects, birds, and other animals. Nothing about organic production prevents or lessens the chances animals can become infected (although the more crowded conditions at conventional farms might mean disease is spread throughout the population faster).

On the other hand, there is evidence that nonorganic poultry is more likely to be contaminated with salmonella than organic poultry.

One reason consumers buy organic meat is because they want to avoid exposure to products that have been tainted with antibiotics. But it is important to keep this issue in perspective. While it is true that organically produced meat and dairy products won’t contain antibiotic residues because producers can’t use them (or, in the case of dairy, can’t use them for one year prior to production), antibiotic residues aren’t much of a problem in nonorganic animals, either. The USDA requires producers to stop supplying animals with antibiotics for a period of time before slaughter, and studies have rarely detected traces of antibiotics or other drugs in conventionally produced meat, poultry, milk, or eggs. The exception is veal—the USDA has found that about nine percent of samples tested have residue of antibiotics.

In any event, in terms of food safety, the issue surrounding the use of antibiotics in meat production isn’t so much the possibility of residues but whether or not the drugs cause higher levels of contamination of antibiotic-resistant bacteria. And studies have shown that a major difference between organic and nonorganic meat is that there is a much lower chance of organic meat being contaminated with antibiotic-resistant bacteria. For this reason, even conventional poultry operators are increasingly committing to not using antibiotics.

Another issue is the use of growth hormones. Organic farmers don’t administer hormones to livestock. Of particular concern among many consumers—and government regulators in other countries—is the use of the hormone recombinant bovine somatotropin (rBST), which is given to dairy cows to boost milk production. This synthetic hormone is approved for use in the U.S., where the Food and Drug Administration and the National Institutes of Health have concluded it is biologically inactive when consumed by humans, and therefore milk and meat from cows supplemented with rBST is safe for human consumption.

There have been some concerns as to how rBST might affect human health. For example, a 20-year-long study published in 1997 by the Journal of Women’s Health reported an association between high levels of the hormone IGF and breast cancer. There is also evidence that IGF plays a role in the formation of colon and prostate cancer tumors. When injected with rBST, cows produce higher levels of IGF, and the dairy products produced in turn contain higher concentrations than dairy products that originate from rBST-free animals.

There is still great debate between the manufacturer of rBST, dairy producers, and consumer-health advocates as to whether the use of rBST could be a detriment to human health. As of yet, a link between the presence of high IGF levels in dairy products and increased risk for cancer really has not been established.

Another issue surrounding the use of growth hormones is how they affect the health of treated animals. Regulators in the European Union, Canada, Australia, and Japan have banned the use of rBST largely over the detrimental effects it can have on the health of the animals; dairy cows treated with rBST are much more susceptible to udder infections and other serious health problems, for example.

The large numbers of concerned consumers, whether rightly concerned about possible human health problems or not, have persuaded several nonorganic dairy producers and sellers to commit to doing away with rBST in their products. Supermarket chains Kroger and Publix have stopped selling milk that comes from cows treated with it. Walmart’s store-brand milk is now rBST-free. Major yogurt companies Dannon and Yoplait have begun using rBST-free milk. And companies such as Starbuck’s and Ben & Jerry’s now use only rBST-free dairy products.

In the U.S., poultry farms are not allowed to use any hormones. So those ads Purdue recently began running that state all its chickens are raised cage-free, without the administration of hormones, may sound like the company is ringing in a new era of fryer-friendly production, but nothing has really changed.