Magazine: Science News; October 16, 1999
 Section: SCIENCE NEWS OF THE WEEK

                 FERTILIZER: HIDING A TOXIC POLLUTANT?
                 -------------------------------------

Perchlorate is hardly a household name. Yet its notoriety is climbing as
the presence of this toxic, thyroid-hormone-disrupting salt leads to the
closure of drinking-water wells in the western United States.

Until now, waterborne perchlorate (ClO[sub 4]-) has been linked almost
exclusively to aerospace activities, since the compound is a major
ingredient in rocket fuels. An Environmental Protection Agency study now
reports evidence of a far more prosaic and potentially widespread
source: garden-variety fertilizers.

Other researchers within EPA and in the fertilizer industry, however,
are challenging the new data. More embarrassing, the authors of the new
study--scientists at EPA's National Exposure Research Laboratory in
Athens, Ga.--told Science News that they will have to retract some of
their positive findings.

Says Steve C. McCutcheon, who heads the Athens EPA team, "We definitely
made a few mistakes" in the first analysis. However, he argues, "we do
have irrefutable evidence" of perchlorate in all fertilizers tested.

Chilean nitrate--historically a common ingredient in some fertilizers--
has been a known natural source of perchlorate for more than a century.
The chemical has even turned up in at least one deposit of potash, a
common fertilizer ingredient. Finally, the aerospace industry, which is
responsible for cleaning up some of the worst perchlorate water problems
so far detected, has recently reported data from two studies finding
perchlorate in fertilizer, McCutcheon notes.

Against this backdrop, the Athens scientists stepped in to analyze nine
fertilizers, most of them intended for lawns and gardens, using three
independent techniques. They also assayed eight fertilizer ingredients
using one or two of the techniques. In the just-published Oct. 1
Environmental Science &Technology (ES&T),the researchers report finding
perchlorate in every sample tested.

This universal contamination should have been the first clue that
something might be wrong, argues chemist Edward T. Urbansky of EPA's lab
in Cincinnati. He notes that some of the ingredients tested, such as
urea, have no mineral sources--and therefore should contain no
perchlorate.

Having reviewed its disputed results, the Athens team will soon ask ES&T)
to "correct" the data for five of the eight fertilizer ingredients,
acknowledging that it can no longer detect perchlorate in them. However,
McCutcheon emphasizes, these retractions will not affect the results for
the fertilizers, which were more fully analyzed.

At EPA's National Center for Environmental Assessment in Research
Triangle Park, N.C., "We have real concerns [about the Athens data] that
are quantitative and qualitative," notes Annie M. Jarabek. The
techniques used to measure perchlorate are still evolving and not yet
unambiguous, says Jarabek, who is heading EPA's toxicological risk
assessment on the compound. Moreover, she wonders why the Athens team
assayed fertilizers that are used by homeowners instead of the brands
that farmers use.

Since learning of the Athens data earlier this year, Urbansky has
analyzed some 45 fertilizers with what he says is a far more sensitive
technique than has previously been used to perchlorate. So far, he finds
"no detectable perchlorate" in anything except a few pure sodium
nitrates. Presumably, he says, they contain the infamous Chilean
nitrate.

These data lead him to suspect "that the Athens group is almost
completely wrong" about fertilizer as a major source of perchlorate.
McCutcheon instead argues that perchlorate concentrations are
inconsistent in the fertilizers--his lab now witnesses variations--and
may trace to seasonal changes in sources of raw materials.

Last month, EPA added perchlorate to its list of contaminants that water
utilities must monitor. As the compound's toxicity is better understood,
Jarabek says, it might come under federal regulation, perhaps as early
as 2003.

~~~~~~~~
By Janet Raloff
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Source: Science News, 10/16/99, Vol. 156 Issue 16, p245, 1/2p.
Item Number: 2377380