Cows on drugs? - antibiotic residues in milk

Nutrition Action Healthletter, April, 1990 by Lisa Y. Lefferts

Cows on Drugs?

Dairy cows get sick. It's a fact of life. Dairy cows also are worth money. So when they become ill, farmers want to get them back "on line" as quickly as possible.

Most of the time, that means treating the cow with an antibiotic or other drug and then waiting a few days or a week until the residues of the medication "clear" the animal's system.

But not all farmers wait as long as they should. (For some drugs, nobody even knows how long to wait.)

So how can we be certain that drug residues haven't somehow found their way into the container of milk we just bought?

Don't ask the Food and Drug Administration. The FDA's official test for drugs in milk can't detect most of the medications that farmers customarily use--either legally or not--to treat sick cows.

It's clear that potentially harmful drugs (including some carcinogens) could be getting into the milk supply. And it's also clear that nobody's systematically looking for those drugs.

That doesn't mean you should stop drinking milk. But it bothers us that the FDA doesn't know how safe our milk is. What's worse: what it does know, it would rather you didn't.

Testing, Testing. The FDA doesn't routinely test milk. Instead, it has an agreement with the states to do their own testing.

But the only thing the official FDA test (which most states use) is good for is detecting penicillin. The problem is: there are dozens of other drugs that farmers use to nurse sick milk cows back to health.

Are traces of these drugs turning up in milk? The FDA, despite its assurances, doesn't have a clue.

Last winter, we decided to look for ourselves. We used a testing method that is more comprehensive and more sensitive than the one recommended by the FDA. Independently, The Wall Street Journal decided to do the same.

The results became front-page news: residues turned up in four of the 20 milk samples we had collected in the Washington D.C. area, and in 19 of the 50 samples collected by the Journal in ten cities around the country. The drugs that showed up were sulfas, penicillin, streptomycin, and erythromycin.

The FDA Makes Its Moo-ve. Only four days after The Wall Street Journal article broke, the FDA announced that it planned to test milk too.

Great, we thought. The FDA is finally getting serious about drug residues in milk. We should have known better.

"A nationwide survey of milk has found no residues of any antibiotics, including sulfa drugs," the FDA proudly announced a month or so later.

But a close look at the FDA's "clean milk" survey shows that the results weren't so "clean." When the FDA used the same testing method that we did (the Charm II assay), 51 percent of its milk samples showed traces of animal drugs.

So how did it conclude that there were "no residues"?

Simple. The FDA said that the Charm II assay was unreliable. In other words, our "positives" were "false," and our tainted milk was really drug-free.

Milking the FDA for the Truth. But the day after the FDA released its "clean milk" survey, the House Subcommittee on Inter-Governmental Relations and Human Resources held hearings on animal drugs in milk.

Under sharp questioning by subcommittee chairman Ted Weiss of New York, the FDA admitted that it discounted the Charm II results simply because the FDA was unable to confirm those results using other tests--tests that were less sensitive to some drugs and that had never before been used on retail milk.

That's like denying what you see under a microscope because you can't also see it with a magnifying glass. In fact, the tests that the FDA used "do not check for certain drugs picked up by the Charm II assay," testified Joseph Settepani, the FDA chemist who first blew the whistle on the FDA's sloppy regulation of animal drug residues in milk.

"I know," he added, "because I helped coordinate the development of the tests... [The FDA] avoided conceding any problem by prematurely relying on a...method that didn't exist a month ago."

Works Like A Charm. In fact, the test we used--the Charm II assay--is reliable. Several states and a growing number of dairies now use it. (WCBS-TV, the CBS affiliate in New York, also used it to test milk, and also found traces of animal drugs.)

The Charm II test can pick up low levels of seven different families of drugs, although it can't identify specific drugs within those families. That makes it an ideal screening test for drugs in milk. More specific tests are required to tell exactly which drug (and how much of it) is present.

Charm II has been thoroughly tested and approved by the Association of Official Analytical Chemists (AOAC), a professional organization that evaluates test methods. Interestingly, the testing methods the FDA used to show "no drug residues" in milk haven't been approved by anyone.

Just Say "Moo." This isn't the first time the FDA has tried to pull a fast one on the public. In March 1988, nearly three-quarters of the milk samples it tested (in a small survey) contained the drug sulfamethazine, which causes cancer in animals.