There has been much outcry over revelations that Chinese businesses fraudulently included melamine and cyanuric acid in animal feeds. But we should be at least as concerned about the "business as usual" ingredients that are routinely fed to the animals we eat.
Today in the United States, almost all animals intended for human consumption are produced within an industrial system reliant on feeds that include a variety of dubious ingredients. Chicken manure, factory wastes, plastics, pet food waste and cyanuric acid - all are commonly deemed acceptable ingredients in feed for animals that end up on our dinner tables.
We now know that it is common practice in China to boost animal feed protein readings by adding the industrial waste products melamine (a nitrogen-rich compound used to make plastics and fertilizer) and cyanuric acid (often used in the United States as a stabilizer for chlorinated pool water). Although neither chemical is very harmful alone, the combination appears to form crystals responsible for kidney failure in pets.
These chemicals got into feed for at least 20 million U.S. chickens, 56,000 hogs and an as yet unknown number of farmed fish destined for human consumption. According to government reports, humans have probably consumed up to 3 million chickens and 345 hogs that ate the chemicals, and all affected hogs were just cleared for human consumption. Government reviews suggest that the risk from this consumption is minimal. Perhaps we got "lucky" this time.
So let us learn from the experience. China is far from alone in allowing waste streams and substances that cannot be categorized as "food" to be fed to hogs, chickens, fish and other animals that people eat - or to animals that produce our milk and eggs.
A paper this month in Environmental Health Perspectives examined the health effects of ingredients in feed consumed by animals destined for the slaughterhouse. It found that animals eat rendered remains from slaughtered animals (including those excluded from human consumption); animal excrement; animal fats that may contain dioxins and PCBs; food contaminated with rodent and roach excreta; byproducts from drug manufacture; and plastics.
The paper also reviews evidence showing that animal feeds are contaminated with pathogens including salmonella and E. coli, antibiotic-resistant bacteria and molds. The feeds often intentionally contain antibiotics and metals (including arsenic for chickens and hogs) to promote growth. The industry's voluntary guidelines state that processed animal waste used in feeds should not include pathogens, pesticides or drugs that could harm animals or be detected in human food. But the guidelines are merely voluntary, and monitoring is inadequate.
We should not assume that food animals can detoxify and make safe whatever we feed them.
For example, arsenic has been found in retail chicken meat, and animal products are top sources of human exposure to dioxins and some other persistent organic pollutants. Eating animals infected with salmonella from feed has been estimated to lead to 134,000 human salmonella infections per year. Further, some contaminants are excreted in manure that is used as fertilizer, and from there can get into the soil, the air breathed by farm workers and nearby residents, the water supply, and food crops eaten by all of us.
There is a great need for more specific information about what is in animal feeds, how much gets into the human food supply, and the potential effects on human health. The Centers for Disease Control and Prevention's National Exposure Report is providing growing evidence of population-wide exposures to a wide range of chemicals; we do not yet know how much of this comes from the food supply. As the food safety infrastructure is re-examined, policymakers should develop a nationwide tracking system requiring manufacturers to document what goes into animal feeds, monitoring the extent to which these ingredients make it into supermarket products, and tracking the potential effects on human and animal health.
Public health professionals should be involved in decisions about which waste streams and other ingredients are safe for animals intended for human consumption. Additional research, policy development, attention to imports and enforcement are essential. The Safe Food Act introduced by Rep. Rosa DeLauro, Democrat of Connecticut, and Sen. Richard J. Durbin, Democrat of Illinois, is an important step forward for food safety, and specifically includes animal feed in the definition of "food."
Government responsibility for food safety and environmental protection must include questioning the overall menu of permissible items in animal feed. After all, when animals eat garbage, so do we.
Dr. Robert S. Lawrence is director of the Johns Hopkins University Center for a Livable Future and a professor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health. Roni Neff is research director at the Center for a Livable Future. They can be contacted at rneff@jhsph.edu.