Dr. Allan S. Felsot, Environmental Toxicologist, WSU
You know you have hit the big time when a Newsweek reporter calls you up for an interview for a story about organophosphate insecticides and the FQPA (Food Quality Protection Act). Intending to be a very cooperative scientist, and dispel the notion that we are stuffy incomprehensible communicators, I was very talkative and eagerly sent the interviewer some of my own essays. Alas, my efforts went unrewarded with nary a use of my ideas yet alone my name in the June 1, 1998 article, "Pesticides and Kids' Risks." The Environmental Working Group (EWG), the advocacy group discussed in this newsletter previously, fared better. Convinced of EWG's wisdom, Newsweek stated, "Despite the administration's 1993 pledge to reduce pesticide use on crops, use is up 10 percent; levels of carcinogenic pesticides in kids' foods have almost doubled." These latter two conclusions come from EWG's recently released report, "Same As It Ever WasThe Clinton Administration's 1993 Pesticide Reduction Policy in Perspective."
Compressed into 30 pages with graphs and tables, the EWG report wants the reader to accept three main premises-pesticide use is rising, pesticide residues in food are increasing, and drinking water is even more polluted than a few years ago. All of these bad things have happened since the Clinton administration announced in 1993 that their goal was to reduce pesticide use, protect children, and promote sustainable agriculture. Implicit in EWG's conclusions is that our world is a riskier place because of Clinton administration policy failures, notwithstanding the FQPA.
I know a lot of progressive growers who would not be shy telling you about the Administration's failures, but I doubt if they would attribute anything out of Washington, D.C. as influencing their choice to use a pesticide. Having children of their own, many growers are just as concerned about health as parents not living on farms. Growers have consistently expressed their desire to reduce pesticide use where possible-after all, they are expensive and a hassle to use. If correct, EWG's conclusions about pesticides would surely be disappointing. A more critical examination of the report, however, suggests that EWG's analysis may be too simplistic, shallow, and perhaps even dead wrong.
Is Pesticide Use Increasing?
EPA has been using pesticide sales as a surrogate for determining trends in pesticide usage. EWG described this technique as an inadequate proxy for actual pesticide usage and called the state of government information primitive. But those inadequacies did not stop EWG from using the EPA data anyway. According to the EWG analysis, agricultural pesticide use jumped from 706 million pounds in 1993 to 790 million pounds in 1996.
Another source of agrichemical usage information is the USDA's National Agricultural Statistics Service (NASS) that makes its database accessible on the internet at http://www.usda.gov/nass/pubs/estindx1.htm#agchem. NASS personnel sample growers within each state using interviews and examinations of actual pesticide use records. The data are subjected to probability analysis to estimate chemical usage and acres treated. The NASS database is developed every other year for fruits and vegetables and every year for field crops.
EWG mentioned the NASS database but chose not to examine the information. That's too bad because if they had, they would have discovered why pesticide use seems to have risen since 1993. Simply stated, if more acres are planted, then the probability of using more pesticide also increases. Crops like corn and soybeans are grown on so many acres that they would tend to inordinately influence aggregate use statistics when production is increased. Minor crops like potatoes rely heavily on soil fumigants and defoliants that have very large per acre application rates. Aggregate pesticide use statistics are meaningless to an understanding of pesticide trends. Rather, individual crops need to be studied.
Corn, soybean, and winter wheat account for more crop acreage than all other crops. Combined with cotton and potato, these crops represent about 60% of all agricultural pesticide use. Combined production of corn, cotton, potato, and soybean increased 10 million acres between 1993 and 1996 (Table 1), even though winter wheat production declined by about 4 million acres.
Table 1. Crop acres and pounds of pesticide used based on estimates from
the
USDA National Statistical Service.
ACRES PLANTED (1000's) |
POUNDS PESTICIDE USED (1000's) |
| CROP | 1993 | 1996 | 1993 | 1996 |
| CORN | 72,989 | 79,830 | 220,571 | 227,876 |
| COTTON | 13,324 | 14,355 | 53,092 | 61,013 |
| POTATO | 1,190 | 1,265 | 55,552 | 79,311 |
| SOYBEAN | 59,411 | 64,519 | 63,817 | 75,613 |
| WINTER WHEAT | 43,952 | 39,611 | 6,551 | 11,775 |
| TOTAL | 190,866 | 199,580 | 399,583 | 455,588 |
The corresponding increase in chemical usage was nearly 56 million pounds, accounting for almost 70% of the increase in usage claimed by EWG. Thus, the major reason aggregate pesticide use went up in 1996 can be accounted for by increases in land under production, not because of some policy failure nor lack of will to reduce use. Of course, changes in weather and pest pressure will cause yearly fluctuations in pesticide usage on any crop.
Do the increases in aggregate pesticide use mean that hazard has also increased as the EWG report implies? Investigation of the details of chemicals used reveals the absurdity of trying to equate aggregate pesticide use and hazard. For example, well over 90% of the pesticides used on corn and soybeans are herbicides with residues rarely found in food. Although insecticides account for about 29% of total pesticide use on cotton, most of the production goes for fiber which is not eaten. Use of sulfuric acid as a defoliant on potato jumped almost 10 million pounds between 1993 and 1996. But in the presence of water, sulfuric acid completely dissociates to harmless, natural sulfate ions and leaves no residue. The large increase in pesticide use on wheat despite the drop in production acreage can be accounted for by large increases in the use of glyphosate and 2,4-D, comparatively safe products easily available to the homeowner. In short, aggregate pesticide use statistics are very poor predictors of hazard.
Are Pesticide Residues in Food Increasing?
EWG analyzed pesticide residue data developed by the USDA Pesticide Data Program (PDP) and the Food and Drug Administration Regulatory Monitoring Program (FDA). Based on the PDP, EWG concluded that the average pesticide residue levels "have increased slightly on fruits and vegetables children consumed heavily, from 1993 through 1996." Based on the FDA data, EWG concluded substantial increases in residues. Despite the discrepancy between the two databases, which actually analyzed different foods, the idea of averaging together the residues of all chemicals to discern trends and make implications about hazards is toxicologically absurd. Each chemical has its own tolerance, ultimately based on different hazards both in degree and type. Thus, allowable application rates will be vastly different among chemicals, resulting in highly variable concentrations of residues. For example, the databases include post-harvest fungicides, which are generally much less hazardous than insecticides used on fruit but always leave residues 10 to 100 times greater. Making sense of pesticide residues can only be accomplished by comparing trends in residues of specific products.
For example, when I used the PDP to analyze trends in azinphos-methyl (Guthion) and chlorpyrifos (Lorsban) residues on apples (see AENews no. 146, June 1998), I found that average levels dropped nearly 50 and 75% respectively between 1992 and 1996. Considering that EWG has stated that 3 bites of an apple can expose thousands of children to "unsafe" levels of organophosphate insecticides, the good news about lower residues of Guthion and Lorsban should be celebrated, not hidden in aggregated averages for all pesticides.
More troubling than EWG's meaningless lumping together of residues from vastly different chemicals, is the observation that some of the data presented may be downright wrong. The most glaring example is a large jump in average pesticide residues shown for apples between 1993 and 1996. The data supposedly came from the PDP. The values for the average residues looked suspiciously high because I knew that most residues were present at only a small fraction of their tolerance level. I decided to test EWG's analysis by examining the trends in maximum residues found in apples by the PDP, reasoning that the average of all the array of individual residues cannot be higher than the average of the individual maximum residues. My analysis showed that the average maximum residue for all pesticides found on apples was 1.2 ppm in 1993, about the same level that EWG claimed was the average of all residues. In 1996, however, the average maximum residue had dropped to 0.58 ppm, whereas EWG showed the average of all residues to be nearly 1.6 ppm. Obviously, a serious discrepancy exits between our analyses. This exercise does illustrate why peer review of scientific reports is necessary to straighten out problems in handling data. EWG's conclusion that pesticide residues are increasing should be validated before being considered suitable for public use.
Is Water More Contaminated with Pesticide Residues Than Ever Before?
Any environmental analytical chemist worth their salt will tell you that pesticide residues exist in surface and ground water, although there are very big differences between regions. Just about any water collected in the Corn Belt will have atrazine residues, but insecticide residues are a rare sight. When insecticides are found, they are hundreds to thousands of times lower than regulatory standards, which themselves already have at least 100-fold safety factors built in.
Some claim that herbicide residues have been increasing in our waterways. Actually, what has increased is our ability to detect ever lower amounts of the residues that were always there. For example, one study showed that when atrazine detection levels were at 1-2 parts per billion, only 1-2% of the aquifers in Iowa were "contaminated" (Kolpin et al., 1995, J. Environ. Quality, v. 24, p. 1125). When detection limits were lowered to 3 parts per trillion, the number of "contaminated" aquifers jumped to 46%.
Does that mean contamination increased? No, because we now know that atrazine probably moved to those aquifers very rapidly, but our ability to see it improved a thousand fold. Is the hazard any greater now than before? No, because human exposure rates have been shown to be up to thousands of times less than what the regulations currently allow (Richards et al., 1995, Environ. Sci. & Technol., v. 29, p. 406). After more than 35 years of atrazine use, not one study has credibly proven any human hazard from drinking water.
The Devil Is In the Details
While EWG seems to be popular with the big media for juicy "facts" about pesticides, the organizations failure to delve into the details of the scattered pieces of data inhibit rather than help growers' efforts to manage their pesticide use. Careful examination of land use statistics, freely available to anyone on the internet, shows that pesticide use generally tracks planted acreage, but other influential factors include weather and pest outbreaks. The USDA PDP shows that for apples, which are recognized as an important children's food, average residues of the most widely used insecticides has been declining. Lumping all pesticides together obscures the true trends. Finally, we have known for a long time that water in the Corn Belt has seasonally high levels of herbicides. Residues are no greater now than over the last 25 years, but analytical detection limits now allow us to include ever smaller and smaller levels.
"The Same As It Ever Was" perceives that things have gone from
bad to worse and the Clinton Administration policies are a failure. While
some may agree with the latter point, I'm hearing EWG singing the same old
song.
Return to the Table of Contents for theAugust 1998 issue
Return to the Agrichemical & Environmental News Index