REALLY DO HAVE
Do organically-grown foods contain fewer residues of toxic crop pesticides than conventionally-grown foods do? The answer is anemphatic yes, according to a scientific study published today in the peer-reviewed journal Food Additives and Contaminants. The study team included analysts from Consumers Union (CU), the Yonkers, NY-based publisher of Consumer Reports magazine, and from the Organic Materials Research Institute (OMRI), an independent research, education and evaluation organization in Eugene, OR.
Organic foods are grown without most synthetic chemical inputs used in conventional farming, and many consumers who buy organic do so to avoid dietary pesticides. But the issue has been surprisingly controversial, with some conservative and media commentators claiming organic foods have justas many residues as foods grown conventionally.
"We have shown that consumers who buy organic fruits and vegetables are exposed to just one-third as many residues as they'd eat inconventionally-grown foods, and the residues are usually lower as well," said Edward Groth III, Senior Scientist at CU and one of the paper's co-authors.
The paper published today is the first detailed analysis of pesticide residue data in foods grown organically and conventionally. "Until now, the scientific community had few empirical data to answer this question," explains Charles Benbrook, a consultant to CU and co-author of the paper. "But in the last few years, enough good data have become available to do a rigorous analysis."
The authors obtained and analyzed test data on pesticide residues in organic and non-organic foods from three independent sources: Tests done on selected foods by CU in 1997; surveys of residues in a wide array of foods on the US market conducted by the Pesticide Data Program of the US Department of Agriculture in 1994 through '99; and surveys of residues in foods sold in California, tested by the California Department of Pesticide Regulation in 1989 through '98. The combined residue data sets covered more than 94,000 food samples from more than 20 different crops; 1,291 of those samples were organically grown. "We've pulled together the best available data on residues in organic produce to generate a clear picture of the category as a whole," says co-author Karen Benbrook, who carried out much of the data analysis for CU.
The USDA data showed that 73 percent of conventionally grown foods had at least one pesticide residue, while only 23 percent of organically grown samples of the same crops had any residues. More than 90 percent of the USDA's samples of conventionally-grown apples, peaches, pears, strawberries and celery had residues, and conventionally-grown crops were six times as likely as organic to contain multiple pesticide residues. The California data (based on tests with less sensitive detection limits) found residues in 31 percent of conventionally grown foods and only 6.5 percent of organic samples, and found multiple residues nine times as often in conventional samples. CU tests found residues in 79 percent of conventionally grown samples and 27 percent of organically grown samples, with multiple residues ten times as common in the former. The levels of residues found inorganic samples were also consistently lower than levels of the same pesticides found in conventional samples, in all three sets of residue data.
"The results are remarkably consistent across all three data sets," says Brian Baker of OMRI, a co-author of the study. "If we take the results as a whole,the evidence is very convincing that-as you'd expect-there are fewer residues by far in organically grown foods."
The USDA and CU tests also included some samples of "green labeled" foods-foods that are not organically grown, but are marketed with claims basedon reduced pesticide use, or "no detectable residues." Foods in this category had residues in 47 percent of USDA samples and 51 percent of CUsamples-intermediate between results for organic and conventional crops.
The authors explored reasons why organic foods contain any pesticide residues at all. When they excluded residues of persistent, long-bann edorgano chlorine insecticides such as DDT from their analysis of the USDA data, the fraction of organic samples with residues dropped from 23 to 13percent. Most residues in organic foods (and some of the residues in conventional foods) can readily be explained as unavoidable results of environmental contamination by past pesticide use, or by "drift" (sprays blown in from adjacent non-organic farms). Some tested samples may also have been mislabeled as organic, either because of fraud or because of lapses in maintaining the identity of foods as they moved from the farm to point ofpurchase. Such problems represent opportunities for producers to improve their performance, says Baker.
What about residues of natural pesticides, used by some organic (and non-organic) farmers? Critics of organic agriculture have suggested that residuesof natural pesticides in organic foods pose risks comparable to those of residues of conventional crop chemicals in non-organic foods. The paperconcludes there is no current evidence to support that assertion, although the authors see this as an interesting question that should be pursued with better data.
"At present there are no good residue data on the botanicals and other natural pesticides, and some of those substances definitely should be more fullyevaluated for potential toxic effects," says Groth. But he emphasized that "There is now no objective evidence of a problem with residues of natural pesticides, whereas health risks associated with residues of conventional pesticides in foods are well-established and the focus of substantial regulatory efforts."
While the analysis for this study was conducted with no funding from outside sources, the CU database that made that portion of the analysis possible was developed with partial support in recent years by since-completed grants from the Pew Charitable Trusts, the Joyce Foundation, and the W. Alton Jones Foundation.
The full paper can be purchased (obtained free by press) from the publisher of Food Additives and Contaminants.
Reducing dietary exposure to pesticide residues is an important goal of public health and environmental officials, farmers and other segments of the food industry, and consumers. Organic agriculture, with its strictures against the use of synthetic chemical inputs, seems to offer a low-residue alternative to conventionally-grown produce; avoiding exposure to pesticides is one major reason consumers buy organic foods. Foods sold with claims of reduced pesticide use or use of integrated pest management (IPM), sometimes certified as containing no detectable residues (NDR), are now on the market aswell. In general, the effects of different agricultural production systems on dietary exposure to pesticides is a question of considerable interest to scientists, regulators and the public.
Surprisingly, few empirical analyses of residue data have addressed this question, mostly because of a dearth of data on residues in organic produce. Inthe absence of better data, public controversy has swirled about this issue, with conservative media commentators and critics of organic agriculture going so far as to suggest that foods grown organically have just as many pesticide residues as conventionally grown foods.
Sufficient good data now exist to resolve the issue empirically. The authors obtained data on pesticide residues in organically grown foods, foods produced with IPM/NDR systems, and foods with no market claim (assumed to be conventionally grown) from three independent sources representingtests of over 94,000 food samples, and carried out statistical analyses of residue patterns.
Data Sources and Characteristics
We obtained test data from three U.S. sources: The Pesticide Data Program of the U.S. Department of Agriculture; the Marketplace SurveillanceProgram of the California Department of Pesticide Regulation; and private tests conducted by Consumers Union.
USDA Data: The USDA Pesticide Data Program collects samples of selected foods from a representative sample of retail outlets across the country.Samples are analyzed with sensitive multi-residue methods and specific methods for additional residues of interest, with extensive quality control stepsand confirmation analyses. The PDP data are widely regarded as the best available data for assessing dietary pesticide exposure. We obtained PDPdata for 1994 to 1999, which included 26,893 samples of 20 different crops. 127 of those samples were identified as organically grown, and 195 were identified as marketed with an IPM or NDR claim. The remaining 26,571 carried no recorded claim and were classified as conventionally grown for ouranalysis.
Cal DPR Data: California DPR testing is part of an enforcement program; as such, it needs rapid sample turn-around and relies on test methods with higher detection limits than those achieved by the USDA PDP. The DPR sampling strategy also emphasizes monitoring of potential problem areas, so itssampling is not precisely representative of all foods sold in California. But DPR tests large numbers of samples of multiple crops each year, and includes many organic samples. (DPR does not identify IPM or NDR samples.) We obtained DPR data for 1989 to 1998, which included results on 67,154samples, covering 19 different crops; 1,097 of the samples were organically grown.
CU Data: Consumers Union conducted focused tests in 1997 designed to see whether there were differences in residues between organic,"green-labeled" and conventionally grown foods. CU tested only four crops, purchased in just six cities over a two-month period, so their sampling did notrepresent the broader US food supply. However, CU tested up to 20 samples of each crop from each market category, providing more samples of theselected organically-grown foods than either the PDP or DPR programs tested in any year. Analytical methods were comparable to those used by thePDP. CU's testing included 67 organic, 45 IPM or NDR and 68 conventionally grown samples.
Taken together, the three data sets provide an enormous amount of data on residues in conventionally grown samples of 20 major crops. The data also include 1,291 samples of organically grown foods and 240 samples with an IPM/NDR claim-enough to support statistical analysis and comparison ofresidue patterns across the three market categories.
Analyses and Results
Raw data were obtained from USDA, Cal DPR and CU and converted to Access data files. We then computed number of samples, number withresidues, number of residues per sample, mean residues, and other results of interest for individual crops and samples of each crop representing thedifferent market sectors. A statistician performed various analyses to determine the statistical significance of observed differences.
Frequency of Positive Samples: All three data sets showed striking, highly statistically significant differences between market categories in the percentof samples that had at least one pesticide residue. Conventionally grown samples consistently had residues far more often than other categories.Overall, across 8 fruits and 12 vegetable crops, 73 percent of USDA's conventionally grown samples had residues. For five crops (apples, peaches,pears, strawberries and celery) more than 90 percent of samples had residues. Cal DPR (using less sensitive analytical methods) found residues in 31percent, and CU found residues in 79 percent, of their conventionally grown samples. Organically grown samples consistently had far smallerpercentages with residues: 23, 6.5 and 27 percent in the USDA, DPR and CU data, respectively. In the two data sets that included samples of the thirdcategory, residues were found in 47 percent of the USDA IPM/NDR samples and 51 percent of the CU IPM/NDR samples.
We performed a second analysis of the USDA data from which we excluded residues of long-banned, environmentally persistent chlorinated organicinsecticides, such as DDT, dieldrin and chlordane (i.e., residues due to environmental contamination rather than to differences in crop productionmethods). With these residues excluded, the fraction of positive organic samples dropped from 23 to 13 percent. The effect of excluding these residueson percents positive in other categories was much less noteworthy (conventional dropped from 73 to 71 percent, and IPM/NDR dropped from 47 to 46percent).
Multiple Residues: Conventionally grown foods often contain residues of more than one pesticide. A conventionally grown apple tested by USDA in1996 was more likely to contain four or more residues than to contain three or less, and some individual samples have been found with as many as 14different residues. We examined the frequency of multiple residues and again found highly statistically significant differences between the marketcategories. Conventionally grown samples had multiple residues in 46, 12 and 62 percent of USDA, DPR and CU samples, respectively. Organicsamples had multiple residues in only 7, 1.3 and 6 percent of the samples in those three data sets. IPM/NDR samples were again intermediate, at 24percent (USDA) and 44 percent (CU).
Residue Levels: We compared residues of the same pesticides found on conventional, organic, and IPM/NDR samples of the same foods. This analysis was somewhat limited by the relative rarity of residues on organic samples, but comparable residues were lower on organic samples abouttwo-thirds of the time in all three data sets. When data from all three sources were combined, the difference was statistically significant. Comparison ofresidues in IPM/NDR and conventional samples from the USDA data set found residue levels in the former were also significantly lower than those in the latter.
Our analysis shows convincingly that organically grown foods have fewer and generally lower pesticide residues than conventionally grown foods. This pattern was consistent across all three independent data sets. Organic foods typically contain pesticide residues only one-third as often as conventionally grown foods do. Foods marketed with an IPM or NDR claim fall in between organic and conventional foods in both the frequency of residues and residue levels. Organic samples are also far less likely to contain multiple residues than conventional or IPM/NDR foods are.
While the risks to health associated with dietary pesticide residues are still uncertain and subject to debate, risk is relative, and lower exposure undoubtedly translates into lower risk. Consumers who wish to minimize their dietary pesticide exposure can do so with confidence by buying organically grown foods.
Our analysis does show, however, that organic foods are not pesticide free. Most of the residues in organic foods (and some of the residues inconventional foods as well) can readily be explained as the unavoidable results of environmental contamination by past pesticide use, or by "drift" (spraysblown in from adjacent non-organic farms). Some foods sold as organic may also be mislabeled, either because of fraud or because of lapses in maintaining the identity of foods as they move from the farm to the consumer.
A potentially significant gap in this analysis is the lack of data on natural pesticides, used by some organic farmers and some non-organic growers aswell. Included are botanical insecticides such as rotenone and pyrethrum, sulfur and copper compounds, and a variety of other traditional pesticidespermitted in organic agriculture. Some commentators have suggested that residues of these natural pesticides are present in organic foods and offsetthe absence of residues of conventional crop chemicals.
We examined that issue and conclude that there is no objective evidence to support the assertion that natural pesticide residues pose a hazard. None ofthe test programs from which we obtained data include data on natural pesticide residues; in fact, there are few analytical methods available to detectthese substances. The botanical insecticides tend to break down rapidly in the environment, are comparatively non-toxic, and are used by a relatively small fraction of growers, ordinarily only as a last resort. Consequently, these substances are not expected to leave residues in foods. They are there for eexempt from tolerances (residue limits) as set by the U.S. Environmental Protection Agency, and no agency routinely tests for them.
The possible risks posed by natural pesticides is an interesting question that should be pursued with both better residue data and more extensive toxicitytesting of some of the natural substances. However, there is currently no objective evidence of a problem with residues of natural pesticides, where as the health risks associated with conventional pesticide residues in foods are well-established and substantial and subject to intensive regulatory efforts aimed at reducing exposure.
While our analysis shows that organic foods clearly have much fewer pesticide residues than other choices on the market today, it also suggests several opportunities for organic growers and others to further reduce residue levels. More steps can be taken to test for and avoid contamination by persistent residues in soils. Enforcement of the new USDA national organic standards should reduce the (relatively rare) incidence of mislabeling, and ensure that consumers who buy organic get what they pay for.
Written by: Consumers Union
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