Concerns over the accuracy of testing equipment for measuring hydrogen sulfide emissions can now be laid to rest.

Independent tests by California scientists confirm that equipment used by the Idaho Department of Environmental Quality, and by the Idaho Department of Agriculture are both accurate. And therefore, the DEQ’s findings of high hydrogen sulfide rates around some dairies in the Magic Valley are accurate also.

Concerns about the accuracy of the DEQ’s testing equipment were raised earlier this month by Department of Agriculture officials who wanted to be sure that the equipment wasn’t giving too high, and therefore, inaccurate readings.

DEQ is currently developing statewide standards for hydrogen sulfide emissions that will affect all industries — including dairy — and municipal sewer systems. Preliminary proposals call for hydrogen sulfide rates not to exceed 10 parts per billion in any 24-hour period no more than once during a 30-day period. Also included in the current DEQ proposal is a ceiling level of no more than 200 parts per billion at any time.

Many industry representatives — including those from the beef and dairy industries — have voiced concern that the levels are too strict. And the question of whether or not DEQ has the legal authority to set and enforce the standards has also been raised at the public hearings on the matter.

Deputy Director Mike Everett from the Ag Department told The Times-News that the rates as proposed could force many dairies and feeding operations, particularly smaller ones, out of business.

For example, Everett said, a small 300-cow dairy for which odor does not exceed “normal agricultural practices,” the wording used in Idaho’s Odor Management Act, would often exceed DEQ’s proposed standards even at a half-mile distance from the farm.

DEQ has chosen to take action on hydrogen sulfide to protect the health of Idaho residents. Although people can suffer eye and throat irritation, nausea and vomiting and shortness of breath at exposure levels of 1,000 to 10,000 parts per billion, the proposed guidelines are much lower.
There is disagreement as to whether or not chronic exposure to hydrogen sulfide is a health risk.
However, most people can smell it at low concentrations of 10 parts per billion. It smells like rotten eggs.


Tim Teater, the toxic air specialist for the DEQ, told The Times-News that "We have to consider everything and make a decision to protect public health while allowing people to do business in a reasonable way. I believe (a hydrogen sulfide) standard is necessary, and we are going to do as the board has asked us to."

A final proposal will be presented to the DEQ board August 6.

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