“This is a GoogleMaps picture of a farm near Goldsboro in North Carolina (map). The two salami-colored ponds on either side are lagoons, but not the kind where you want to swim. They’re open basins full of feces. To get a feel for the size, try comparing them with the cars in the dirt lot. As the Google Map will demonstrate, there are several more of these lagoons situated nearby. (You can imagine the breeze downwind of these facilities must have a rather bracing quality to it, especially on warm summer afternoons.)
Livestock agriculture in the US produces manure on a truly titanic scale — some ~133 million tons’ dry weight per year, ~13 times more than the sanitary waste produced by the human population . Sometimes this manure enters the environment directly. Poorly constructed lagoons sometimes leak manure, for example, or overflow during rainstorms. Manure is also spread on many crop fields as fertilizer; from there, some of it enters lakes and streams in runoff. Since animals like pigs routinely receive low doses of antibiotics as part of their feed, manure often contains both antibiotic-resistant bacteria and low concentrations of antibiotics.
A number of studies have looked at concentrations of antibiotics in soil on farmland fertilized with manure; the results vary, depending on how you extract the antibiotic from the soil samples. How quickly the antibiotics break down in the environment also depends on the drug. Generally the antibiotic concentrations in soil samples are very low, although the manure often contains antibiotic-resistant bacteria into the bargain. The vast majority of these bacteria, of course, are poorly adapted to life in the soil and perish without heirs in their new environment.
What consequences (if any) does all this have for us? It’s difficult to say, partly because soil is teeming with bacteria anyway, and soil bacteria are a bountiful reservoir of antibiotic resistance genes in any case. The truth is we don’t really know. But it illustrates an interesting point: no farm animal is an island. Antibiotics and antibiotic-resistant bacteria from farm animals are introduced into soil and water all the time. Nor is this all, for antibiotic-resistant bacteria from the gut of a pig or a cow can work their way into the human population by a much more direct route: through contact with farm workers and through the meat consumers eat.
First, I have a sexy picture I’d like to share with you. It’s a little shocking, so don’t say I didn’t warn you:…”