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The report below has been reprinted from the original analysis conducted by the Consumers Union of the United States, Inc., Public Service Projects Department, Technical Division.

"Which Foods Have the Highest TI Values? Seven foods consistently had high or very high TI's each time tested: Fresh peaches (both domestic and imported); frozen and fresh winter squash grown in the U.S.; domestic and imported apples, grapes, spinach and pears; and U.S.-grown green beans. Among these, U.S. peaches and frozen winter squash had TI Values about 10-fold higher than even the other "high" scores..."

This Report is very long, and has been broken down into different sections:

Quick Links

|| Summary || Introduction to the USDA Pesticide Data Program || Methodology & Toxicity Index ||
|| Results and Discussion || Recommendations || Tables: Pesticide Contamination in Fruits & Vegetables ||


Results and Discussion

Quick Links to Sections on this Page

|| Comparative Toxicity of Different Foods || Illegal Residues || Health Implications || Multiple Residues ||
|| Differences between Domestic & Imported Foods || Trends || Risk Drivers || Pesticide Use Data ||

A. Comparative Toxicity Loading of Different Foods

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The TI values for different foods shown in Table 4 range from 0.01 to 5,376--a range of more than 500,000-fold. However, the majority of values fall between 10 and 300 on the TI scale. The scale is relative, and there is no firm dividing line between "acceptable" and "excessive" degrees of pesticide toxicity loading. Nevertheless, in our judgment, values of less than 10 can be considered very low toxicity loading, i.e., the food is very "clean." Values above 100 indicate "high" toxicity loading, increasingly serious as scores get larger. TI values between 10 and 100 fall on a continuum rising from "low"
through "moderate" toxicity loading.

Foods with the lowest TI scores include:


Food Item
Toxicity Index ( TI )
Canned/Frozen Sweet Corn (U.S., 1995)
Canned/Frozen Sweet Corn, (U.S., 1994)
Milk (U.S., 1996)
Milk (U.S., 1997)
Broccoli (U.S., 1994)
Orange Juice (U.S., 1997)
Bananas (Imports, 9 countries, 1994)
Bananas (Imports, 7 countries, 1995)
Canned Peaches (U.S., 1997)
Canned/Frozen Peas (U.S., 1994)
Grapes (Mexico, 1994)
Apple Juice (U.S., 1996)
Apple Juice (Mexico, 1997)
Apple Juice (Germany, 1997)
Apple Juice (Argentina, 1996)
Apple Juice (U.S., 1997)

Corn, bananas and peas all have an inedible exterior husk, which tends to keep pesticide residues away from the edible portions of the foods. Processing typically further reduces residues. Only three of 1,015 samples of corn tested in two years had any detectable residues. The very low score for U.S. broccoli reflects the rarity of residues in that food; the two most
frequently detected insecticides were each found on less than 2 percent of 659 samples. Apple juice (imported and domestic) typically has only low residues of a few pesticides. The score for canned peaches, which is 1/1,000 that for fresh peaches, reflects effects of processing, a longer time between harvest and consumption, and differences in pest management on peaches grown for processing as opposed to those grown for the fresh market (see Section F, below).

A few other foods had scores nearly as low as those listed above: Frozen/canned peas tested in 1995-96 (TI's of 22 and 21); frozen winter squash from Mexico (1997, 21); orange juice from Brazil (1997, 23); fresh winter squash from Honduras (1997, 23); U.S. sweet potatoes (1997, 25); Canadian tomatoes (1997, 26); and wheat (1995-97, 18, 29 and 32).

The highest Toxicity Indices (those over 100 on our TI scale), listed in descending order, were for the following foods/origins/years:

Food Item
Toxicity Index ( TI )
Fresh Peaches (U.S., 1995)
Fresh Peaches (U.S., 1996)
Fresh Peaches (U.S., 1994)
Frozen Winter Squash (U.S., 1997)
Fresh Winter Squash (U.S., 1997)
Grapes (U.S., 1994)
Fresh Spinach (Mexico, 1996)
Apples (U.S., 1994)
Fresh Spinach (U.S., 1995)
Apples (U.S., 1996)
Frozen/Canned Green Beans (U.S., 1997)
Apples (U.S., 1995)
Fresh Spinach (U.S., 1996)
Fresh Peaches (Chile, 1996)
Pears (U.S., 1997)
Pears (Chile, 1997)
Fresh Peaches (Chile, 1994)
Fresh Peaches (Chile, 1995)
Fresh Spinach (U.S., 1997)
Grapes (Chile, 1996)
Grapes (U.S., 1995)
Apples (New Zealand, 1994)
Fresh Green Beans (U.S., 1994)
Apples (New Zealand, 1996)
Apples (New Zealand, 1995)
Fresh Spinach (Mexico, 1997)
Celery (U.S., 1994)
Grapes (Chile, 1995)
Grapes (U.S., 1996)
Fresh Green Beans (U.S., 1995)
Frozen/Canned Green Beans (U.S., 1996)
Canned Spinach (U.S., 1997)
Pears (South Africa, 1997)
Potatoes (U.S., 1994)
Grapes (Chile, 1994)
Grapes (South Africa, 1996)
Tomatoes (Mexico, 1997)
Pears (Argentina, 1997)
Oranges (U.S., 1994)
Carrots (Mexico, 1995)
Tomatoes (Mexico, 1996)
Lettuce (U.S., 1994)
Fresh Spinach (Mexico, 1995)


Seven crops (peaches, apples, pears, grapes, winter squash, spinach and green beans) appear among the highest TI scores repeatedly, with scores above 200 essentially every time they were tested. For all but green beans and winter squash, imports and U.S. samples both have high (though often not equally high) TI scores. In most cases, the consistently high scores are attributable to the insect problems typically associated with growing these crops, and to the insecticides (mostly organophosphates) used on them. (See Section H, below, for further details.)

B. Illegal Residues

Only 1 percent of the residues detected by the PDP in 1994 violated the legal limits, or tolerances, established by the U.S. EPA for the specific pesticides on the specific foods in which they were detected. In 1995 and 1996, the violation rate was about 4 percent, and in 1997 it was 5 percent.

Spinach was tested in the latter three years, and in 1995 and 1996, more than half of the violative residues were on spinach (a situation that improved in 1997). There were no noteworthy differences in violation rates between U.S. and imported samples.

Most violations (95 percent or so of the illegal residues each year) do not involve residue levels that exceed a legally permitted maximum level. Instead, most illegal residues are pesticides detected on foods on which they are not registered for use with the EPA. Such violations can occur because of residues left in soils from past uses on other crops, and from "drift," wind-blown contamination of a field by pesticides applied legally to a different crop on adjacent fields.

However, some residues show up consistently in a significant fraction of samples of a crop on which they are not registered for use, at levels quite similar to those found in crops on which the chemical is legally registered for use. This strongly suggests that some growers used the pesticide, even though it is not legally registered for use on that crop. We found this kind of pattern of significant illegal use of several insecticides on spinach. At least one illegal residue was present in about 25 percent of spinach samples in 1995 and 1996, and many samples had residues of more than one illegally- used pesticide. In 1997, the violation rate was about half as high as in the two previous years, but still far greater than for other foods.

Some residues of pesticides banned years ago still show up in foods. Chlorinated hydrocarbon insecticides, such as DDT, dieldrin and chlordane, all banned from food uses in the 1970s, are very persistent in soil, and some agricultural land is still contaminated with them. For example, DDT and its breakdown product DDE are found in carrots, sweet potatoes and potatoes, and dieldrin was detected in 74 percent of tested samples of frozen, and 37 percent of fresh, winter squash. Such persistent banned pesticides have no tolerances, but the Food and Drug Administration has set "action levels," or
limits above which the FDA considers these residues too high to allow the foods on the market. None of the dieldrin, DDT or other residues of banned organochlorine insecticides violated action levels. But these "legal" residues can contribute substantially to the toxicity loading of the foods in which they occur.

C. Health Implications of Differences in Pesticide Toxicity Loading

What is the health significance of a high TI score? The only solid scientific answer to that question is, we are not sure. Pesticides, of course, are poisons; they are designed to kill living organisms. It is certain that all pesticides can have adverse health effects on people at a high enough level of exposure. The critical question is whether exposure associated with the residues found in foods is low enough to ensure an adequate safety margin between actual exposures and levels that can cause health damage. Exposures Above Official "Safe" Levels. The Reference Dose (or RfD, defined on page 8), is generally regarded as a science-based estimate of a presumably "safe" daily intake for an individual pesticide. While there is room to debate that view--not all RfD's may adequately account for the higher vulnerability of children, for instance -let's stipulate for now that an RfD is a definition of "safe" pesticide exposure. In that case, the PDP data provide some striking evidence that safety margins are not adequate.

For example, the average methyl parathion residue on U.S. peaches tested in 1994-96 was 0.055 parts per million. At that concentration, a 100- gram peach would contain 5.5 micrograms of methyl parathion. The current EPA RfD for methyl parathion is 0.00002 mg/kg/day (or 0.02 ug/kg/day, since 1 mg = 1,000 ug). That means a 20-kg (44-pound) child should not consume more than 0.4 micrograms per day of this insecticide. Eating just one medium-sized peach with an average methyl parathion residue, though, would give that 20-kg child a dose of this intensely neurotoxic insecticide almost 14 times higher than the RfD.

In fact, even the lowest methyl-parathion residue found on peaches in 1996, the most recent year tested, 0.004 ppm, would still deliver a Reference Dose of the insecticide to a 20-kilogram child who ate a 100-gram peach. Methyl parathion was found on 41 percent of U.S. peaches in 1996. This means roughly two of every five children who eat a U.S. peach will exceed the RfD for methyl parathion by eating that single food item. The maximum methyl parathion level the PDP found on peaches in 1996, 0.5 ppm, would deliver 125 times the RfD, and the highest 10 percent of residues all exceed 35 times the RfD.2

Methyl parathion on peaches is perhaps an extreme example, but is far from the only case in which a young child can ingest more than a safe dose (i.e., more than the RfD) of a specific pesticide by eating a single serving of a specific food. Table 6 highlights some pesticide/crop combinations and shows how often they can deliver an unsafe dose. For instance, dieldrin was found in 37 percent of fresh winter squash and 74 percent of frozen winter squash samples tested for it in 1997. The majority of positive samples had residues high enough to give a 20-kg child more than the RfD of dieldrin in a 100-gram serving of squash. The odds of this occurring are 28 percent for fresh squash, and 48 percent for frozen squash. Grapes from Chile tested in 1996 contained residues of the organophosphate insecticides chlorpyrifos, dimethoate and omethoate, each at levels sometimes high enough to exceed the respective RfD's. The combined odds (i.e., the chance that a 20-kg child eating 100 grams of Chilean grapes would exceed the RfD for at least one of the three) are about 10 percent. Similarly, if that child were to eat 100 grams of fresh spinach, the odds are about 1 in 12 that he or she would exceed the RfD for dimethoate, omethoate or methomyl.

While odds like 1 in 12 or 10 percent may not seem very large, there are 20 million children under the age of six years in the United States. The likelihood that one of every 10 children who eats Chilean grapes, four of ten who eat U.S. peaches or half of those who eat frozen U.S. winter squash will get more than the theoretically "safe" dose of a very toxic insecticide, is not a trivial concern. And these simple calculations ignore the fact that children (and most everyone else) eat many different foods in a day, several of which may expose them to residues that could have additive effects.

In theory, RfD's have safety factors built into them, and eating a food that exceeds the RfD for a pesticide does not automatically mean a child will suffer adverse effects. But the public needs to be confident that the levels of pesticides in foods are "safe enough," i.e., that there is in fact a wide margin of safety between actual exposure and harmful levels, even for children and other vulnerable sub-populations. Clearly, such confidence in the "safety margin" of current residue levels is not warranted. In fact, if "safe use" is defined as practices that seldom leave residues that can exceed the RfD, it appears that methyl parathion cannot be used safely on foods that children eat, and that winter squash can't be grown safely on dieldrin-contaminated croplands.

What about exposures that don't exceed the RfD? While many people assert that the levels of pesticides in foods are generally too small to have any adverse effects, there is no scientifically credible way to rule out the risk of subtle harmful effects in at least some fraction of the exposed population. Not all forms of health damage are readily measurable. It is also very difficult to assess possible interactive effects of multiple residues found in the variety of foods consumed in a typical day.

Young children, and fetuses, are more sensitive to toxic effects of chemicals than adults are, because the young are growing and developing rapidly, processes that are vulnerable to disruption by toxic agents. Since young people's bodies are smaller than adults' bodies, children get greater doses of residues by consuming a given food than an adult would. Children also eat fewer foods, and eat more of certain foods that tend to be relatively heavily contaminated with pesticides, than adults do. Most insecticides are nerve poisons, and a central concern is potential damage to the developing nervous system. Current scientific knowledge is generally inadequate to define exposure levels that are free of risk of adverse developmental effects on the nervous system. RfD's are typically based on tests on adult animals; most pesticides have not been fully tested for effects on immature animals. These gaps in scientific knowledge suggest that a cautious attitude toward dietary pesticide exposure, even at relatively "low" levels, is quite sensible. While we cannot draw a clear line between "safe" and "unsafe" on our Toxicity Index, risk associated with dietary exposure to pesticide residues is relative. Higher toxicity loading scores clearly represent greater risks than lower scores, and in our judgment, differences of the magnitude shown here are meaningful. Excluding the extremely low scores for canned corn, the range of TI values for foods tested by the PDP over this four-year span is more than 5,000-fold. Consumers are justified in wanting to minimize their exposure to pesticides through food choices. Our TI values can help guide them to sound choices that can measurably reduce the risk of harm.

D. Multiple Residues

One of the reasons pesticide risk assessment is so difficult is that the average person's daily diet consists of many different foods, and many of those foods contain pesticide residues. People are not exposed to a single pesticide chemical at a constant dose level, the way laboratory animals are in toxicity tests; instead, they consume a constantly changing mixture of many different pesticides at variable levels.

The PDP data make this multi-chemical exposure picture very clear. PDP analyses show that as many as five or six different pesticides typically are detected in 10 percent or more of most crops, and for many foods, it is " normal" for individual samples to have multiple residues. Table 7 shows the frequency of detection of multiple residues in the individual samples of different foods tested by the PDP in 1996. The median number of residues (that is, the number for which half the samples had fewer and half had more residues) on tomatoes and oranges was one, while the median apple sample had four residues, and the median peach sample had three residues. Three percent of apples had eight or more different residues. And one sample of spinach had a whopping 14 different pesticides on it.

The data in Table 7 suggest that a person whose meals in a given day included apple juice, a salad with carrots, spinach \ and tomato, some green beans and a peach, would be exposed to 10 different pesticide residues, if those foods had typical (median) contamination patterns.

E. Differences Between Imported and Domestic Foods

One interesting question is whether imported foods have higher TI scores, indicating greater loading of pesticide toxicity, than domestically grown samples of the same crops. U.S. agricultural interests have argued that stricter U.S. regulations on pesticides in foods (which may be required as the U.S. EPA implements the Food Quality Protection Act of 1996) will hurt U.S. growers in the world market. Growers in other countries, facing fewer restrictions on pesticide use, the argument goes, can produce foods more cheaply. An implication of this argument is that imported foods may be more heavily contaminated with pesticide residues.

While U.S. government and agribusiness spokespeople are fond of boasting that "The U.S. has the safest food supply in the world," the USDA has also stated that there are no meaningful differences in pesticide residue problems between domestically-grown and imported foods. Our analysis of the PDP data tells a different story.

One way to compare U.S. and imported foods is to see which group has consistently higher Toxicity Indices. The list of foods with highest TI scores, on page 14 above, shows 12 food/country/year cases that have TI's greater than 500. Eleven of those 12 cases are U.S.-grown foods. The one imported food among the top dozen (Mexican spinach in 1996) had much lower scores the other two years it was tested. Foods that might fairly be characterized as "loaded" with pesticide residues, based on our Toxicity Index, are almost all "Made in the USA." Table 1 shows 39 cases in which more than 10 samples of a specific food imported from a specific country were tested; we used a sample size of 10 as our cut-off for comparing imports and larger numbers of U.S. samples.

Of those 39 U.S./import comparisons, Table 4 shows that U.S. samples had higher Toxicity Indices in 26 cases (67 percent). Again, the available data fail to support the hypothesis that imported foods in general are more likely to
be contaminated with pesticides.

However, as Table 4 also shows, there are notable differences from crop to crop. In a few cases, imports have consistently higher TI values; in more cases, U.S. samples have consistently higher values; and occasionally, there is no consistent pattern (U.S. TI's are higher one year, and imported TI's higher the next). The size of the difference between U.S. samples and imports also varies from food to food. Let's look at some specific cases:

Cases in which U.S. samples have higher TI scores:

Peaches. The U.S. TI values over three years of testing exceed the TI values for imports from Chile by more than 10-fold. Winter Squash. For fresh samples of this vegetable, U.S. samples had a TI 42 times as high as that of Mexican samples. For frozen products, the U.S. score was 143-fold higher than that of Mexican samples. Apples. The TI values for U.S. apples over a three-year testing span are consistently about twice as high as those for apples from New Zealand, the leading source of imports. The number of imported samples is small, but the consistency of the scores from year to year and the consistent pattern of residues (i.e., the same three insecticides account for most of the score in all three years for both sets) suggest that this is a real difference.

Pears from four countries were tested in 1997. The U.S. had the highest TI. Pears from Chile had a marginally lower TI, and those from South Africa and Argentina had TI's less than half that of U.S. samples. Fresh Green Beans. In both years sampled, TI's for U.S. samples were substantially higher than those for Mexican samples, by ratios of about 3-fold and 6-fold in 1994 and 1995, respectively.

Oranges. Imports from Australia in 1995 had a TI 3/4 as large as that of U.S. oranges tested that year. Apple Juice. Scores for apple juice from all countries are quite low. In 1997, imports from Germany and Mexico had TI's lower than that of U.S. apple juice. (Imports from two other countries had TI's higher than that of U.S. juice, though; see below.) Grapes. Imports from Mexico had consistently much lower TI's than U.S. grapes had, in three years of tests. South African grapes, tested in 1996 only, also had a modestly lower TI than U.S. grapes did that year. (TI's for grapes from Chile, the leading source of imports, present a more complex picture; see discussion below.)

Tomatoes. Canadian tomatoes tested in 1997 had a TI half as large as that for U.S. tomatoes that year. (However, Mexican tomatoes had a much higher TI than either U.S. or Canadian samples did; see below.) Cases in which imported samples had higher TI values:

Carrots. Canadian imports had consistently higher TI scores over the three years tested. In two of those years, the Canadian TI's were about twice as high as the US TI's. In 1994, the difference was very small. Carrots from Mexico, tested in 1995 only, had a TI substantially higher than Canadian and U.S. samples.

Tomatoes. Mexican tomatoes tested in 1996 had about twice the TI of U.S. tomatoes. In 1997, the gap widened to about three-fold.

Broccoli. Mexican samples, tested only in 1994, had a TI more than 20 times higher than U.S. samples (but the U.S. score was a very low 2).

Apple Juice: Imports from Hungary and Argentina in 1997 had TI's higher than the U.S. TI that year. Juice from Argentina also had a higher TI in 1996. Since all of these TI values are relatively low, the differences are not very meaningful.

Orange Juice. U.S. samples tested in 1997 had a very low TI of 2, while Brazilian samples had a 23; but, again, 23 is still a comparatively low score.

Cases where the U.S. samples had higher scores in some years and imported samples had higher scores in other years: Fresh Spinach. U.S. samples had high scores of 554 in 1995, 495 in 1996 and 349 in 1997. Mexican samples had a moderately high TI of 103 in 1995, a very high 623 in 1996, and a 256 in 1997. Small sample size for the imports limits the precision of the Mexican TI's. If all three years' data are combined, the average U.S. TI is 460, and the Mexican average is 327.

Grapes. The comparison of U.S. grapes with imports from Chile is very interesting. In 1994, the TI for U.S. samples was almost 9 times that of Chilean grapes' TI, but by 1996 Chilean grapes had a significantly higher TI than domestic grapes. (This is most likely a valid long-term trend reflecting reduced pesticide use in U.S. grape production; see Section G, below.) F. Differences Between Fresh and Processed Foods The PDP data we examined include 16 fresh fruits and vegetables, and 8 processed fruits and vegetables (plus milk, wheat and soybeans). The processed foods include apple juice, orange juice, and frozen or canned varieties of corn, sweet peas, green beans, winter squash, spinach, and peaches. Fresh samples of six of these foods were also tested, making comparisons between fresh and processed versions possible.

In general, processed foods have lower levels of pesticide residues than comparable fresh foods. Growers who have contracts with processors often don't need to ensure that their foods are cosmetically perfect, and this allows them to omit some pesticide treatments, including some late-season insecticide applications. Many processors, responding to consumer demand for foods with minimal pesticide residues, have contracts with growers that specifically limit pesticide applications. Processing itself also often involves washing, peeling and cooking the food, steps that all tend to reduce pesticide residues. Two of the processed foods tested in the PDP years we examined do not have unprocessed varieties for comparison, but both (corn, and sweet peas) have quite low TI scores. (However, the score for peas increased by 250 percent from 1994 to 1995-96; see "Trends," below.) The other cases show some very interesting differences among the specific foods. Peaches. The TI for canned peaches in 1997, was 5, an astonishing 1,000-fold lower than scores for fresh peaches grown in the U.S., and 100-fold lower than the TI's for imported peaches from Chile. This difference reflects different pest management needs and practices between peaches grown for canning and those grown for the fresh market. Orchardists who produce cling peaches for canning grow a different variety than those grown for the fresh market, one that has somewhat less severe pest problems. The fruit doesn't need to be cosmetically perfect, and many canners forbid the use of certain pesticides, including methyl parathion (which was not found in any of the 745 samples of canned peaches the PDP tested in 1997). The processing itself involves a vigorous wash that scours off the peaches' skin and removes most residues, and the long span of time between harvest and consumption allows further breakdown of any residues that remain.

Differences for other processed foods were less dramatic than that for peaches, but still noteworthy: Apple Juice. TI scores for 1997 U.S. samples are more than 25-fold lower than those for U.S. fresh apples (in 1996, 50-fold lower). Imported apple juice from Argentina, Hungary, Germany and Mexico had TI scores ranging from about one-twentieth to about one-eighth that of fresh apples from New Zealand.

Orange Juice. The TI for U.S. orange juice, first tested in 1997, is an extremely low 2, roughly 25-fold lower than the TI for U.S. fresh oranges tested in 1996 and 70-fold lower than that of 1994 oranges. Orange juice from Brazil had a score half as high as that of U.S. fresh oranges (Brazilian fresh oranges were not tested).

Canned Spinach from the U.S., first tested in 1997, had a high TI of 204, but that is less than half of the average TI for fresh U.S. spinach tested in 1995 through 1997. The remaining two cases are exceptions to the general rule that processed foods tend to have lower pesticide residues:

Frozen/Canned Green Beans grown in the U.S., tested in 1996 and 1997, had TI's of 222 and 529. Fresh U.S.-grown green beans scored 294 in 1994, and 222 in 1995. (Unfortunately, no fresh green beans were tested in 1996 or 1997.)

The scores for the processed beans are much higher than expected for a processed food, given the scores for the fresh commodity. Table 5 shows that the high scores are explained primarily by residues of methyl parathion in the frozen/canned green beans. No methyl parathion was detected in any fresh green beans in 1994 or 1995. In 1996, this insecticide was found in 3.4 percent of the frozen/canned samples, and accounted for 49 percent of the TI score. In 1997, it was found in 4.6 percent of samples, the average residue level three was times as high as in 1996, and it contributed 82 percent of the score. These increases in residues are consistent with USDA's pesticide use data, which show increasing applications of methyl parathion on U.S. green bean acreage (See Section I, below, and Table 8.) The increased score for methyl parathion accounts for all of the jump in scores between 1996 and 1997. Without methyl parathion, the TI's for frozen/canned green beans in 1996 and 1997 would have been 113 and 96, respectively. It appears, therefore, that expected lower scores for processed green beans were "cancelled out" by increasing use of a very toxic pesticide on this crop.

Winter Squash was tested in 1997 for the first time, and both frozen and fresh varieties were sampled. Both types had extremely high scores, and the score for frozen product was much higher--3,012, versus 1,706 for fresh winter squash. The insecticide dieldrin accounts for 86 to 90 percent of the total score in each case. Dieldrin, a chlorinated organic pesticide banned in the U.S. in the 1970s, is very persistent in soil, and is taken up through the roots by some crops--including winter squash varieties. Producers of some part of the U.S. winter squash crop seem to be farming lands with a history of dieldrin (or aldrin, which breaks down to dieldrin) applications. Frozen squash has a higher score because dieldrin was detected in 74 percent of the samples, versus in 37 percent of the fresh samples (mean residue levels were roughly comparable).

G. Trends

One very interesting question that the public might look to the PDP data to answer is whether the overall problem of pesticide residues in foods is getting better, or getting worse. Unfortunately, the PDP was not designed to answer that question. The foods tested change from year to year, and that makes it difficult to track trends, even for individual crops. If one adds up the TI values for all crops tested year to year, the total has declined slightly over the four years we examined. But the total is the sum of the TI's for different crops in different years, and TI values among crops vary widely. Any "trend" may therefore result more from the crops chosen for testing than from improvements in the overall pesticide residue picture.

No foods were tested in all four years that we examined. Seven foods were tested in three consecutive years (apples, carrots, grapes, oranges, peas and peaches, all tested 1994-96, and fresh spinach, tested 1995-97). If one compares the total TI for the six U.S.-grown crops tested from 1994 through 1996, there is an apparent downward trend, from 6,717 in 1994 to 6,326 in 1995 and 5,749 in 1996, a decrease of 14 percent over the three years. But that "trend" is almost entirely attributable to the change in TI scores for U.S. grapes, which dropped from 1,552 in 1994 to 329 in 1995 and 228 in 1996. If grapes are excluded, the total score for the other five U.S. crops increased by 7 percent over this three-year period.

It is more instructive to examine the specific crops on which there are three years of data:

Apples. There is no notable overall trend. Total TI values held relatively steady over the three-year test period, for both U.S. samples and imports. In both cases, a small cluster of individual pesticides is responsible for the bulk of the total TI in all three years (see Table 5).

Carrots. There was a slight downward trend (-17 percent) for U.S. samples, and a slight increase (15 percent) for Canadian samples, although the number of imported samples is too small to be sure that this apparent trend is real.

Grapes. There is a steep decline in the TI's for U.S.-grown grapes, from 1,552 in 1994 to 228 in 1996. We believe this reflects actual changes in pest-management practices among U.S. grape producers. In recent years grape growers have made great strides in adopting less chemical-intensive integrated pest management strategies. Comparing the TI factors for the individual pesticides found on grapes (Table 5), the percent positive and mean residue levels for the insecticides methyl parathion, azinphos-methyl and dimethoate all declined substantially in U.S. grapes from 1994 to 1996. These trends account for most of the decline in the TI scores, and they are consistent with trends in pesticide use data on the crop. We believe the PDP data do show a major reduction in the toxicity loading of U.S. grapes over recent years.

Individual components of the overall TI (Table 5) also explain the upward trend in TI values for Chilean grapes (from 181 in 1994 to 339 in 1996). Three insecticides (dimethoate, omethoate and chlorpyrifos) and the fungicide iprodione all increased substantially in frequency of detection in Chilean grapes over the three-year span. Overall, the pattern is consistent and suggests that the trend is real, at least for these three years.

Oranges. The TI's for U.S. samples declined from 138 in 1994 to 38 in 1995, then rose to 49 in 1996. The insecticide formetanate hydrochloride was detected in 10.6 percent of 663 samples tested for it in 1994, and its TI value was 107, or 77 percent of the total for the food. In 1995, the same chemical was found in only 3.5 percent of samples and the average residue was only one-fifth as high as the year before, and in 1996 no formetanate hydrochloride was detected in any of the 511 samples tested. This change in the residue pattern for one pesticide accounts for most of the decline in TI values for oranges. (A higher mean residue level for the fungicide imazalil accounts for the rise from 1995 to 1996.) While short-term trends in pest problems may account for the decline in use of formetanate hydrochloride, this pesticide is very toxic and ecologically disruptive, and orange growers have been working hard at finding safer alternatives to its use. The trend in residue data shown here is a hopeful sign that their efforts are succeeding.

Peaches. No real trend is apparent in the very high TI values for the U.S. peaches tested from 1994 through 1996. The scores rose from 4,390 in 1994 to 5,376 in 1995 and dropped back to 4,848 in 1996. One pesticide, the insecticide methyl parathion, accounts for more than 90 percent of the total TI for this food in all three years. While the frequency of detection was consistent from year to year, the average residue level rose in 1995 and then dropped somewhat in 1996, driving the changes in the overall TI score. On the basis of USDA pesticide use data, it appears that applications of methyl parathion on U.S. peaches declined sharply between 1995 and 1997. But residue data from the Food and Drug Administration's (FDA) testing program show a five-fold rise in the mean methyl parathion residue on peaches from 1996 to 1997. This suggests, perhaps, that while fewer pounds were applied, applications were made closer to harvest, resulting in higher resides. The FDA tests far fewer samples than the PDP does. Given these complex and limited data, it is not possible to project a trend in methyl parathion residues in U.S. peaches beyond 1996. It would be valuable for the PDP to sample this crop again in the near future.

The TI values for imported peaches from Chile tested from 1994 to 1996 show a slight drop in 1995, then a big increase in 1996. TI values for the individual pesticides found on Chilean peaches show that the same two chemicals, iprodione and azinphos-methyl, account for over 70 percent of the total TI each year. The decline from 1994 to 1995 is attributable mainly to a drop in the average residue level for azinphos-methyl (which remained lower in 1996, although the percent of samples positive for this insecticide rose 50 percent over the three years.) The increase in 1996 is attributable primarily to a 34 percent increase in the average residue level for iprodione. Our conclusion: These year-to-year changes probably represent responses to differing pest problems in the three years, rather than an underlying trend.

Green Beans. Fresh green beans grown in the U.S. were tested in two years, 1994-95; frozen/canned green beans from the U.S. were tested in the next two years. While these two foods differ and their TI values are not strictly comparable, they are the same crop, and one very interesting trend in residue patterns emerges. No methyl parathion was detected in any samples of fresh green beans in 1994 or 1995. But this very toxic insecticide showed up in frozen/canned green beans in 1996, and both its frequency of detection and mean residues increased from 1996 to 1997. Methyl parathion residues alone account for the rise in the TI from 222 in 1996 to 529 in 1997. Since these changes correlate strongly with USDA pesticide applications data for methyl parathion on green beans, we believe this trend is real.

Peas. The TI value for frozen/canned peas was a very low 6 in 1994, but increased to 22 and 21 in the next two years. As in the case of green beans, the explanation is use of methyl parathion on this crop. No samples had methyl parathion residues in 1994, and it was detected in only 1 percent of the samples in 1995 and 1996. But this insecticide still accounts for half the total TI for peas in both of the latter years, small as those totals are. Here too, residue patterns match use data trends for methyl parathion on peas.

Spinach. U.S. fresh spinach tested in 1995 through 1997 had high but decreasing TI values, 554, 495 and 349. Imported samples from Mexico had a moderately high 103 in 1995, a very high 623 in 1996, and a 256 in 1997. Since sample size is very small for the Mexican imports (14, 21 and 12), we can't make anything of the year-to-year fluctuations there. But the trend in U.S. values is driven by declining scores for permethrin and dimethoate, two of the top four TI components in each of the three years. The frequency of detection for each has held fairly steady, but mean residue levels declined 39 percent for permethrin and 71 percent for dimethoate. U.S. spinach growers appear to be making progress toward reducing applications of at least some risk-driving insecticides on their crop.

Overall, then, we have a mixed bag: There are three cases where TI values are declining, most likely due to increased reliance on Integrated Pest Management by growers of the crops (grapes, oranges and spinach). There are three cases where residue patterns changed little over three years (apples, peaches and carrots). And there are two cases where Toxicity Indices have risen sharply because of increasing use of methyl parathion on the crop (peas and green beans). These few data points are interesting, but not sufficient to discern any overall trends in pesticide residues in the U.S. diet over the four- year period we examined.

H. Risk Drivers

Individual crops tested by the PDP contained as many as 37 different pesticide residues, and several crops consistently had more than 20 different pesticides detected on them. But in essentially every case, a small number of specific chemicals--from one to three or four--accounts for most of the TI score. We have coined the term "risk drivers" to describe any pesticide chemical that accounts for 10 percent or more of a food's overall TI in any year. The higher the TI value for a food, the more important the role of its risk drivers in overall dietary exposure to pesticide residues.

As Table 5 makes clear, the same pesticides tend to be risk drivers in more than one food, and year after year. For the 27 foods tested by the PDP in the four years we examined, roughly fifteen different pesticides show up repeatedly as major TI components of multiple foods. From the standpoint of policy, the fact that a few chemicals account for the most toxicity loading in many foods is important for setting priorities. Exposure and risk can be reduced substantially by focusing on comparatively few pesticide uses on a limited number of high-consumption foods.

In this section, we profile the risk-driving pesticides found in foods tested by the PDP in 1994 through 1997. They are discussed roughly in order of their overall contributions to toxicity loading on the tested foods.

Parathion-methyl. Also called methyl parathion, this highly toxic organophosphate insecticide is the leading factor in the TI's for U.S. grown peaches (1994-96), U.S. apples (94-96), U.S. pears (97), U.S. grapes (94; second-ranked in 95), frozen/canned green beans (96-97) and frozen/canned sweet peas (95-96). It is also a notable factor in the TI for U.S. carrots (94) and U.S. wheat (96-97), and a minor factor in imported and U.S. tomatoes (96-97) and U.S. apple juice (97). Often, it accounts for more than half of the food's TI, by itself; in peaches, methyl parathion alone contributes over 90 percent of the TI's each year. Methyl parathion was rarely detected on imported produce sampled by the PDP.

In our scoring system, methyl parathion has the highest Chronic Toxicity Index of any pesticide detected by the PDP (see Table 3). It has the lowest EPA RfD (0.00002 mg/kg/day) among the organophosphate insecticides, and the second lowest RfD overall (only heptachlor epoxide's RfD of 0.00001 is smaller). The very low RfD for methyl parathion is based on animal studies showing adverse effects on the developing nervous system at very low doses. Methyl parathion is also among the most potent organo- phosphates in terms of its acute toxicity.

In 1998, the EPA reviewed the RfD's for all members of the organo- phosphate and carbamate families of insecticides, as required by the Food Quality Protection Act (FQPA). The FQPA says that EPA must make sure that pesticide limits protect children's health, and requires that the agency add an extra 10-fold safety factor to limits for all pesticides, unless there is a sound scientific basis for using a different safety factor. Last August, the EPA issued a preliminary decision in which it applied an additional 10-fold safety factor to the RfD's for 11 insecticides. Methyl parathion is among the 11; so is chlorpyrifos, another of the top risk-drivers in the foods tested by the PDP. For another 10 insecticides, EPA applied an additional 3-fold safety factor. That group includes methamidophos, another risk-driver that we profile below. For another 27 insecticides, EPA has not decided to apply any additional safety factor yet, though that decision may not be final.

Methyl parathion is not a suspected carcinogen, but it is listed as an endocrine disrupter by Colborn et al. (1993). In our scoring scheme, that fact increases its Chronic Toxicity Index threefold. Five of the top 12 risk-drivers in our analysis are suspected endocrine disrupters.

Dieldrin. All food uses of this chlorinated organic insecticide were banned by the EPA in the 1970s, but it persists in soils in some locations. Some crops, notably winter squash, absorb dieldrin into the edible parts of the plant via the roots. Dieldrin accounts for 86 percent of the very high TI for fresh winter squash grown in the U.S., and 90 percent of the even higher TI for U.S. frozen winter squash, both tested only in 1997. (Winter squash from Mexico tested the same year had minimal dieldrin residues.) Dieldrin was the largest TI component for U.S. potatoes in 1994, and made smaller contributions to TI scores for U.S. carrots (94), U.S. spinach (95-97), sweet potatoes (96), tomatoes (97) and soybeans (97).

Dieldrin has a very high CTI in our scoring system (it ranks third, behind methyl parathion and heptachlor epoxide), because it has a very low chronic RfD (0.00005 mg/kg/day), and it is a potent carcinogen. In fact, the carcinogenicity component accounts for 80 percent of its Chronic Toxicity Index. It has not been listed as a suspected endocrine disrupter. Iprodione, the only fungicide among the top risk-drivers, is a leading contributor to the TI's for Chilean grapes (94-96), a major factor in TI's for Chilean and U.S. peaches (94-96), and a somewhat lesser factor in the scores for U.S. grapes (95-96) and South African pears (97). It is also detected, at far lower levels, on green beans (U.S. and Mexican, 94-95) and U.S. carrots (95-96). Iprodione consistently ranks second to parathion-methyl in the TI for U.S. peaches. The TI contributions for iprodione on peaches range from 150 to 229--larger than the TI's for all residues in many foods.

Iprodione is quite low in acute and chronic toxicity, but it is classed by EPA as a "probable human carcinogen," which accounts for most of its Chronic Toxicity Index in our scoring system. In 1996, iprodione residues were found on two-thirds of Chilean grapes, 20 percent of U.S. grapes, and about 80 percent of peaches from both countries. Widespread use on these crops and fairly high average residues (0.8-0.9 ppm, on peaches) explain this chemical's large contribution to toxicity loading.

Azinphos-methyl. This organophosphate insecticide is the top risk driver on pears from the U.S., South Africa, Chile and Argentina (1997) and is among the top risk drivers for U.S.-grown and New Zealand apples (1994- 96) and for apple juice (domestic and imported, 96). It is one of the biggest factors in the TI's for Chilean peaches in all three years, and a much smaller factor in the TI's for U.S. peaches. It was a risk-driver for U.S. grapes in 94, but not in later years. It is also used on green beans, spinach and tomatoes, but accounts for a much smaller part of the overall TI in those cases.

Azinphos-methyl, also called Guthion, is almost as acutely toxic as methyl parathion, but is only 1/75 as toxic on a chronic basis, comparing the current EPA RFD's for the two insecticides. It is neither a carcinogen nor an endocrine disrupter, based on current knowledge.

Heptachlor Epoxide is a breakdown product of a chlorinated hydro- carbon insecticide, heptachlor. As with dieldrin, DDT and other members of this chemical family, heptachlor use on food crops was banned in the U.S. during the 1970s. But residues of these very long-lived pesticides remain in soils, and some crops absorb them through their roots. Among the foods the PDP tested, only winter squash (fresh and frozen), tested in 1997, contained heptachlor epoxide residues, but the TI values (362 for the frozen, 142 for the fresh squash) are as high as or higher than TI's for all residues combined in many other foods.

Heptachlor expoxide has the lowest chronic RfD of any pesticide detected by the PDP in these four years, 0.00001 mg/kg/day. It is also a potent carcinogen, but not known to be an endocrine disrupter. These toxic attributes combine to give it the second highest CTI in our system, close behind methyl parathion (see Table 3).

Methomyl, a carbamate insecticide, is one of the top three TI factors for U.S. grapes (94-96), and the top TI factor for Mexican grapes in 1996. It is an important factor in the TI's for U.S. lettuce (1994), Mexican spinach (95-97), and U.S. spinach (95-97), and a less important factor in the scores for U.S. and Mexican green beans (94). It is also detected on peaches from Chile and the U.S. and on U.S. apples, but contributes only in a very minor way to the TI's for those foods.

Methomyl's RfD is 400 times larger than that for methyl parathion (i.e., it is 1/400 as toxic), but it is listed as an endocrine disrupter by Colborn et al.(1993), which boosts its Chronic Toxicity Index in our scoring scheme. In acute toxicity, it is on a par with methyl parathion and azinphos-methyl. Permethrin. This synthetic pyrethroid insecticide is the predominant factor in the TI's for both Mexican and U.S. spinach in 95-97. It is a smaller factor in scores for celery and lettuce, tested only in 94.

Permethrin is quite low in acute toxicity and is only 1/2,500 as toxic as methyl parathion, in terms of chronic RfD; it's the least-toxic pesticide among the prominent risk drivers. But EPA classes permethrin as a possible human carcinogen, which accounts for most of its Chronic Toxicity Index in our scoring scheme. It dominates the TI for spinach because it was detected on 40 to 60 percent of the Mexican and U.S. samples, respectively, and was found at relatively high concentrations (averages of from 1.5 to 2.4 ppm in three years of U.S. samples).

Dimethoate, another organophosphate insecticide, is a top TI factor for Chilean grapes (94-96), Mexican and U.S. green beans (94), U.S. spinach (96-97), Mexican spinach (96), U.S. lettuce (94), U.S. sweet peas (94-96), U.S. and Argentine apple juice (96-97), and German and Hungarian apple juice (97).

Dimethoate, and its breakdown product omethoate (see next profile), are among the more toxic organophosphates, with RfD's only 25 and 15 times greater, respectively, than that for methyl parathion. Neither one is classed as a carcinogen or an endocrine disrupter, based on current data. Omethoate. This organophosphate is sometimes used on its own as an insecticide, but is also a breakdown product of dimethoate, and use of the latter often explains its presence. It tends to be found on the same foods as dimethoate. It is the leading TI factor for both Chilean (94-96) and Mexican grapes (94-95), and is one of the top three TI factors for U.S. spinach (95-97) and U.S. processed peas (94-96). It is a major factor in the TI for apple juice from Argentina (97) and is also detected on apples, tomatoes, green beans and lettuce, but is a smaller factor in the total TI's for those foods. Its toxicity profile was discussed above.

Chlorpyrifos, another organophosphate insecticide, is a risk driver for imported (New Zealand) apples (94-96), and a smaller component of the TI for U.S. apples in those years. It is also detected in apple juice, and is a top factor in the score for imported (Argentine) juice in 1996. It is the top factor in the TI's for Mexican tomatoes (96-97) and U.S. soybeans (97). It is also an important component of scores for Chilean grapes (94-96) and U.S. wheat (95-96), and a minor factor in the scores for Chilean and U.S. peaches (94- 96), Chilean pears (97) and U.S. sweet potatoes (97). It was found on from 2 to 8 percent of fresh spinach samples in 1995-97 (with the lowest rate in 97). It makes only a small contribution to the TI's for spinach, but its use on spinach is not legally permitted.

Chlorpyrifos is one of the more toxic organophosphates, with an RfD (including the FQPA-mandated extra 10-fold safety factor) only 15 times as large as that for methyl parathion. It is neither a carcinogen nor currently listed as an endocrine disrupter. Its high Chronic Toxicity Index reflects its potent neurotoxicity.

Dicofol, a chlorinated organic insecticide, is the leading risk driver on pears from Chile (97) and a major contributor to the TI's of U.S. grapes (94- 96), U.S. apples (94, 96), Chilean peaches (95-96), and U.S. tomatoes (96). On a chronic basis dicofol is moderately toxic, 1/60 as toxic as methyl parathion. It is also a suspected endocrine disrupter, which boosts its CTI. On crops where the PDP detected it, dicofol was present fairly infrequently (3 to 11 percent of samples), but at relatively high residue levels (0.3 to 0.5 ppm) on samples where it is present.

Carbaryl, a carbamate insecticide, is a leading factor in the TI for apples from New Zealand (94-96) and for both U.S. and imported apple juice (96-97). Carbaryl also contributes TI components of 29-41 points to the total for U.S. peaches in 1994-96; this factor is overwhelmed by methyl parathion on peaches, but it is larger than the total TI for several other entire foods. Carbaryl also accounts for about 85 percent of the very low TI for canned peaches. It is used on many other crops as well, and makes a smaller contribution to the TI's for grapes (U.S. and Chile), green beans (U.S. and Mexico), pears from Argentina, oranges, sweet peas and sweet potatoes (all from the U.S.).

Carbaryl is comparatively low in chronic toxicity (1/700 as toxic as methyl parathion), but it is listed as a suspected endocrine disrupter. Endosulfan is a chlorinated hydrocarbon insecticide. It is a top risk driver for U.S. and Mexican green beans in 94-95, and Mexican spinach (95- 97), and a lesser factor in TI's for U.S. spinach in (95-97), and Mexican and U.S. tomatoes (96-97). It is the largest factor in small scores for imported winter squash from Mexico and Honduras in 1997.

Endosulfan is comparatively low in chronic toxicity, with an RfD 300 times greater than methyl parathion's. It is listed as an endocrine disrupter. Acephate, another organophosphate insecticide, is a risk driver for U.S. celery (94), U.S. fresh green beans (94-95), and U.S. processed green beans (96-97). On green beans, it is the largest single component of the TI in 94 and 95. It is used on many other crops but typically contributes only minimally to overall TI's.

Acephate is relatively toxic among the organophosphates, about 1/60 as toxic as methyl parathion. It is neither a carcinogen nor an endocrine disrupter.

Methamidophos, another organophosphate, is used on its own as an insecticide; it is also a breakdown product of acephate, and residues of the two pesticides tend to occur on the same crops. It is the leading TI factor for U.S. tomatoes (96-97) and the second-ranked factor for Mexican tomatoes (96-97). Methamidophos is one of the top TI factors for U.S. fresh green beans (94-95), Mexican fresh green beans in 1995, and U.S. processed green beans (96-97). Its toxicity profile is very similar to acephate's.

I. Pesticide Use Data

The National Agricultural Statistical Service (NASS), part of the U.S. Department of Agriculture, publishes surveys of pesticide applications on major U.S. crops. Data for fruits and vegetables are compiled in alternating years. We obtained NASS pesticide use data for fruits for 1993, 1995 and 1997, and for vegetables for 1994 and 1996, and added them to our database. Crop-to-crop differences and trends in pesticide applications can help confirm inferences drawn from the PDP residue data. Use data for some risk- driving insecticides on key crops are shown in Table 8. While residue data are a better index of the potential for dietary exposure, and therefore of relative risk to consumers, the use data show some interesting patterns.

For example, azinphos-methyl, carbaryl and chlorpyrifos applications on apples held fairly steady from 1993 through 1997, but dimethoate use on apples decreased by 75 percent and methyl parathion applications more than doubled in the same period. This suggests that methyl parathion is replacing some uses of dimethoate on apples, and is consistent with the dominant role methyl parathion plays in the TI's for apples from 1994 through 1996. Over the same three years, the TI's for dimethoate on apples declined from 15 to 2.5, and the percent of samples with residues of this insecticide shrank from 12 percent to 3 percent--almost perfectly in synch with use data.

Methyl parathion use has also increased steeply on pears and green beans, and decreased on peaches. The effects of this use trend showed up in the TI's for processed green beans, and methyl parathion is the top-ranked factor in the TI for U.S. pears in the one year they were tested. Insufficient recent data are available to assess whether the contribution of this chemical to the extremely high TI's for U.S. peaches may be shrinking.

The use on potatoes of two very toxic insecticides, methamidophos and aldicarb, increased dramatically from 1995 to 1997. The PDP carried out a special test of potatoes in 1997, testing only for aldicarb. They tested 342 samples, and found one or more aldicarb breakdown products in 20 samples, a detection frequency of 6 percent. (No aldicarb was detected in U.S. potatoes tested in 1994 and 1995.) They also tested individual servings (i.e., single potatoes) and found that residues in individual samples varied from 0.1 to 7 times the mean level for composite samples. This variability means some children eating a potato have a risk of getting a very high dose of aldicarb, which has implications in terms of potential acute toxicity. This situation clearly requires ongoing surveillance.

Progress toward less reliance on high-risk insecticides is evident in the decreasing use of azinphos-methyl on grapes, peaches and pears; the declining use of dimethoate on apples, grapes, green beans and peas; and decreases in methamidophos and chlorpyrifos use on tomatoes.

Comparable data are not available for pesticide applications in other countries, but the NASS data provide some additional insights into changing pest-management practices in the U.S., and can help explain some of the residue patterns that show up in the PDP data.


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Bibliography and References

1 This report was compiled in February, 1999, by the Consumers Union of the United States, Inc. Public Service Projects Department, Technical Division Edward Groth III, PhD, Project Director Charles M. Benbrook, PhD, Consultant Karen Lutz, MS, Consultant The analysis was supported in part by the Pew Charitable Trusts, the Joyce Foundation and the W. Alton
Jones Foundation.

2 The PDP did not test fresh peaches in 1997, so 1996 data are the most recent available. However, data on pesticide applications (from another branch of USDA) suggest that total pounds of methyl parathion used on peaches declined 44 percent from 1995 to 1997. The Food and Drug Administration's pesticide residue testing program tested fresh peaches in 1996 and 1997. FDA data show a 34 percent decrease in frequency of detection of methyl parathion in peaches (from 28 percent in 1996 to 18 percent in 1997.)

However, the same data show that the mean residue of methyl parathion on peaches increased five-fold, from 0.04 ppm in 1996 to 0.21 ppm in 1997. This suggests that methyl parathion use patterns on peaches may have shifted to fewer applications, but closer to harvest time. The FDA's sample size is smaller (only 35 samples positive for methyl parathion), and we consider the 1996 PDP data the best indicator of the current status of methyl parathion residues in peaches. A new PDP look at peaches would be valuable.


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