Friday, May 13, 2011

USDA's Pesticide Data Program

Each year, USDA's Pesticide Data Program publishes data on pesticide residues, principally in fruit and vegetable crops, selected in part because of their frequent consumption by children.  It is difficult to know how worried consumers should be about the results.  Here are some thoughts and questions on the most recent 2008 residue detections for fruits and vegetables.

For some pesticides, EPA sets safety tolerances for the maximum amount of residue that should show up on food.  For other pesticides, EPA sets no tolerance, meaning that there should not be any residue of that pesticide at all.

First, we look at data on total residue detections.  Many fruit and vegetable samples have multiple pesticide residues, but the amounts may be small, usually far within the Environmental Protection Agency's safety tolerances.  Let's say for the moment that we are not very worried about these total detections, but instead want to know about detections that violate EPA standards.



All samples
Residue detections


#
#
per 100 samples
Asparagus
372
39
10.5
Blueberries
726
1736
239.1
Broccoli
554
797
143.9
Celery
741
3821
515.7
Green Beans
741
1392
187.9
Green Onions
186
272
146.2
Greens, Collard
240
540
225.0
Greens, Kale
318
622
195.6
Nectarines
672
1603
238.5
Peaches
616
2155
349.8
Potatoes
744
1410
189.5
Spinach
747
1850
247.7
Strawberries
741
3703
499.7
Summer Squash
554
1050
189.5
Sweet Corn, Fresh 152
1
0.7
Sweet Potatoes
184
92
50.0
Tomatoes
740
903
122.0
Total 9028 21986 243.5

Second, therefore, we look at residue detections that exceed EPA's established tolerances, for pesticide uses that have a tolerance.  These detections are more worrisome when they happen, but they do not happen very frequently.  Fewer than 1% of samples had this type of residue detection exceeding an established tolerance.



All samples
Residue detections exceeding an established tolerance


#
#
per 100 samples
Asparagus
372
0
0.0
Blueberries
726
3
0.4
Broccoli
554
0
0.0
Celery
741
2
0.3
Green Beans
741
2
0.3
Green Onions
186
0
0.0
Greens, Collard
240
11
4.6
Greens, Kale
318
10
3.1
Nectarines
672
0
0.0
Peaches
616
0
0.0
Potatoes
744
7
0.9
Spinach
747
16
2.1
Strawberries
741
2
0.3
Summer Squash
554
5
0.9
Sweet Corn, Fresh 152
1
0.7
Sweet Potatoes
184
0
0.0
Tomatoes
740
1
0.1
Total 9028 60 0.7

Third, we look at residue detections for pesticides that have no EPA tolerance.  The lack of a tolerance may mean that the chemical is judged to be of greater safety concern.  The USDA found many such residue detections -- almost 5 such residue detections per 100 samples, which seems like a lot of detections in violation of EPA standards.  However, the tests are quite sensitive, and the residue amounts may be very small.  USDA is not greatly worried: "In most cases, these residues were detected at very low levels and some residues may have resulted from spray drift or crop rotations."




All samples
Residue detections for pesticides with no tolerance


#
#
per 100 samples
Asparagus
372
1
0.3
Blueberries
726
21
2.9
Broccoli
554
17
3.1
Celery
741
123
16.6
Green Beans
741
23
3.1
Green Onions
186
9
4.8
Greens, Collard
240
34
14.2
Greens, Kale
318
45
14.2
Nectarines
672
2
0.3
Peaches
616
61
9.9
Potatoes
744
45
6.0
Spinach
747
33
4.4
Strawberries
741
5
0.7
Summer Squash
554
15
2.7
Sweet Corn, Fresh 152
1
0.7
Sweet Potatoes
184
1
0.5
Tomatoes
740
1
0.1
Total 9028 437 4.8

Environmental groups are not convinced. The Environmental Working Group uses these data as one of several sources in constructing its "dirty dozen" and "clean fifteen" lists of fruits and vegetables.


I wish the USDA's PDP reports did a better job helping readers to understand the implications of residue detections for pesticides that have no EPA tolerance. If USDA's position is that these are negligible detections, attributable to inconsequential pesticide drift, then it should explicitly set a threshold for these negligible detections. On the face of it, without that type of interpretation, I am reluctant to accept that these detections are all inconsequential. For example, notice that 16% of celery samples and 14% of many leafy greens had this type of violation.  Could those really all be spray drift?  That would seem surprising.  It would help to have a more blunt assessment from USDA experts: "These detections are negligible, but we want these other detections to fall into compliance in the near future."

Also, the Environmental Working Group throws a good heavy punch this week regarding the produce industry's government-funded information campaign to convince people not to worry about pesticides.  Agriculture departments, including the California Department of Food and Agriculture and USDA, should steer clear of anything that smacks of misleading propaganda on this topic.  For example, now that I have had time to study the residue data, I suspect last November's report from the Alliance for Food and Farming is overconfident that these residues are harmless.  A better approach might be to undertake some vigorous enforcement, drive down the frequency of violative residue detections, and then boast about the results. Indeed, if industry leaders took a long-term perspective, I think they would encourage USDA to do so.

Pesticide residues are not my leading food safety concern -- they rank behind foodborne illness on my list of things to worry about -- but I do take them seriously.  Among agricultural economists, I sometimes hear an outright dismissal of concern about pesticide residues as completely silly, but I think scientists who study cancer risks and toxicity take these concerns more seriously.  For example, here are the conclusions of the 2008-2009 report from the President's Cancer Panel, issued by the federal government's National Cancer Institute:
The entire U.S. population is exposed on a daily basis to numerous agricultural chemicals. Many of these chemicals are known or suspected of having either carcinogenic or endocrine-disrupting properties.
The report identified several problems that hinder policies to address environmental chemical contaminants: (a) inadequate funding and staffing, (b) fragmented and overlapping agency authorities, (c) excessive regulatory complexity, (d) weak laws and regulations, and (e) undue industry influence.

3 comments:

  1. Hi Parke,

    You may be interested to know about new sessions popping up the American Dietetic state affiliate conferences rebuking the "dirty dozen" and offering heavy criticism that this type of outreach deters consumers from eating fruits and vegetables.

    The top speaker is Anthony “Tony” Flood, the
    Director of Food Safety Communications for the
    International Food Information Council (IFIC). He is a BS in Communications. (http://www.foodinsight.org/Resources/Detail.aspx?topic=IFIC_Review_Pesticides_And_Food_Safety)

    They also have this very entertaining scientist, educator and entertainer from UC Davis, Carl Winter: http://carlwinter.com/

    I began hearing about this session from some friends in Texas. ADA leading the pack towards progress.

    The session is called "How Risky is Our Food? Clarifying the Controversies of Chemical Risks" and the FoodInsight has done the same type of presentation on aspartame, caffeine, BPA, high fructose corn syrup and antibiotic usage in animal agriculture, food dyes and biotech.

    Talk soon!

    ReplyDelete
  2. Dr. Wilde, I just wanted to say thank you for posting this summary of the 2008 data. I did a similar (although not as nice and succinct as yours) analysis of the USDA data, criticizing the EWG for their unnecessary alarmism which is based on poor data analysis and seemingly intentional misunderstanding of tolerances and lower detection limits. I think it is very important for people to know that fresh fruits and vegetables are, overall, safe foods, and that the benefits far far outweigh the risks.

    Any plans to post a similar summary for the 2009 data? It's on my to-do list, but I won't get to it until late July at the earliest.

    ReplyDelete
  3. I do not see the "cocktail effect" addressed - the affect of one "safe" concentration on top of another "safe" concentration, etc. Nor a discussion of pregnancy, small children, compromised health complications, etc.

    ReplyDelete