By Al Brooks
In our embrace of organic farming, we used to shun chemical fertilizers, and rightly so. They do harm to soil microorganisms and produce bloated crops with less flavor and nutrition. But some new studies have uncovered problems with manure, our favorite fertilizer for organic crops, that now cause us to examine where a particular batch of manure comes from and what went into the livestock that produced it.
According to tests conducted at the University of Minnesota, many food crops absorb the antibiotics leaching into the soil from the manure of livestock fed these chemicals. Antibiotics are introduced into livestock feed in order to increase growth and prevent infections. We have long understood the environmental harm, done by the application of excess manure, to our waterways because of runoff. But the researchers at the University of Minnesota discovered that vegetables such as corn, potatoes and lettuce absorb antibiotics when grown in soil fertilized with livestock manure.
Close to 70 percent of the total antibiotics and related drugs produced in the United States are fed to cattle, pigs and poultry, according to the Union of Concerned Scientists. And about 90 percent of that is excreted in the urine and manure. According to an article in Rachel's weekly #993:
"The Minnesota researchers planted corn, green onion and cabbage in manure-treated soil in 2005 to evaluate the environmental impacts of feeding antibiotics to livestock. Six weeks later, the crops were analyzed and found to absorb chlortetracycline, a drug widely used to treat diseases in livestock. In another study in 2007, corn, lettuce and potato were planted in soil treated with liquid hog manure. They, too, accumulated concentrations of an antibiotic, named Sulfamethazine, also commonly used in livestock."
Heat (cooking and canning) and other processing can reduce the levels of some antibiotics in foods, but Sulfamethazine, for one is not affected by heat. Of greatest concern are those vegetables that are commonly eaten raw, like lettuce and cabbage, and those tubers that are in contact with the soil and may absorb greater quantities, like potatoes, carrots, and radishes.
Health officials fear that eating vegetables and meat laced with drugs meant to treat infections can promote resistant strains of bacteria in food and the environment. Past studies have shown overuse of antibiotics reduces their ability to cure infections. Over time, certain antibiotics are rendered ineffective. But scientists have evidence that there may be other serious consequences. Antibiotics also may have contributed to the explosive rise in asthma and allergies in children over the last 20 years. Again, quoting from Rachel's Weekly:
"Researchers at Henry Ford Hospital in Detroit, following 448 children from birth for seven years, reported that children who received antibiotics within their first six months had a higher risk of developing allergies and asthma."
"Such health concerns led the European Union (EU) in 2006 to ban antibiotic use as feed additives for promoting livestock growth. But in the United States, nearly 25 million pounds of antibiotics per year, up from 16 million in the mid 1980s, are given to healthy animals for agriculture purposes, according to a 2000 report by the Union of Concerned Scientists."
Composting of manure, since heat is generated by this process, can break down some of the antibiotics. But if a farmer or gardener wishes to be free of this contamination entirely, s/he must know the pedigree of the manure applied to the food crops. Until we put in place regulations similar to those in the EU, where antibiotics can be given only to sick animals, we must each, individually apply the precautionary principle and avoid using even "natural" fertilizers whose source is unknown.