The steroid growth hormones given to cattle on factory farm
operations have long been of interest to environmental scientists. Because
these drugs pose the most serious risk to aquatic life, past studies have
focused mainly on their transport to bodies of water via surface runoff.
However, a recent study confirms the viability of a vector no one had ever
considered before – dust.
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| Researcher Brett Blackwell setting up monitoring equipment. Credit: Jerod Foster |
Cattle given drugs such as steroids do not break them down
completely. The compounds are excreted in their manure, which can then dry and
be pulverized into airbourne dust.
Researcher Philip N. Smith, an ecotoxicologist at Texas
Tech, first considered the possibility when he was out duck hunting downwing
from a cattle feed yard. The dust in the air was so thick that it coated his
teeth, and he began to wonder what was in it. He and colleages at the Environmental
Protection Agency set up sampling equiptment at five feed yards in Texas and
Oklahoma, which remained collecting samples and taking measurements for two
years.
After analysis was complete, they determined that the most abundant
hormone was the estrogen 17α-estradiol, which appeared on 94% of filters
with a mean concentration of 21-ng/g particulate matter.
The biggest risk posed by such airbourne contaminants is to
aquatic life. The particles were large enough that people are unlikely to
inhale them, as they would not travel very far. Only those people working on
feedlots or living very nearby would be exposed to appreciable quantities, but
the health impacts of such exposures are not well-understood.
The largest feed yard in the study was found to emit 63 mg
of 17α-estradiol per day in dust alone. This amount is comparable to
what might be transported each day in runoff, making dust a significant source
of potential environmental harm.
By: Aisling Williams
Source
Lockwood, Deirdre. “Cattle Feed Yard Dust Can Transport
Steroids Into Environment.” Chemical & Engineering News: (2015) n. pag. 7
July. Web. 25 July 2015.
