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Estimation of cancer risks and benefits associated with a potential increased consumption of fruits and vegetables. Rick Reiss Exponent September 25, 2012. Acknowledgments . Partially funded by the Alliance for Food & Farming, which represents farmers and farm groups
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Estimation of cancer risks and benefits associated with a potential increased consumption of fruits and vegetables Rick Reiss Exponent September 25, 2012
Acknowledgments • Partially funded by the Alliance for Food & Farming, which represents farmers and farm groups • Collaborators include Dr. Carl Keen (UC Davis) and Jason Johnston, Kevin Tucker, and Dr. John DeSesso (Exponent)
Paper Accepted to Food and Chemical Toxicology Link: http://www.sciencedirect.com/science/article/pii/S0278691512006394 dx.doi.org/10.1016/j.fct.2012.08.055
Outline of Presentation • Review of consumer perception of pesticide residues • Methodology of paper: • Estimation of cancer prevention benefits • Estimation of cancer risk from pesticides • Results • Caveats and uncertainties • Conclusions
Introduction • Most fruit and vegetables contain small levels of pesticide residues • There is significant consumer concern about the potential effect of these residues • Any concern must be balanced by the substantial health benefits of eating fruits and vegetables
Several Public Campaigns Aimed at Pesticide Residues • Environmental Working Group’s “Dirty Dozen” • No consideration of toxicity or risk • Not transparent how the “dirty dozen” is determined • Organic Trade Association’s “Dietary Risk Index” • Throws out non-detects from analysis • Conflates acute and chronic consumption data
Residues Are Prevalent but Small – Pesticide Data Program (2008 PDP)
Cancer Risk Perception • Many consumers see pesticide residues on food as a significant risk concern • About 70% of Spanish respondents considered avoiding pesticide-treated fruits and vegetables as a means to prevent cancer (Garcia et al., 1999) • Organic food buyers estimated the risk of mortality from consuming conventionally-grown food to be similar to a 1 pack per day smoker (Hammitt, 1990) • The Alar scare in 1988 resulted in “near hysteria” (American Dietetic Association, 2007).
Cancer Risk Perception • Many consumers do not identify fruits and vegetables consumption as a way to prevent cancer: • About ½ of survey respondents did not identify fruit and vegetable consumption as a protective effect against cancer • It is time to correct some of these perceptions, to the extent possible
Prevention of Cancer from Fruit and Vegetable Consumption • Hundreds of studies have been conducted • WCRF/AICR meta-analysis of epidemiologic studies found “probable” evidence of a benefit for several cancers • Case for prevention has weakened somewhat over time, but is still strong • “Probable” evidence for mouth, pharynx, larynx, esophageal, stomach, and lung cancer (fruits and/or vegetables) • Relative risks provided for these cancer types
Cancer Sites with Decreased Risk for F&V Consumption(“Probable”)
Cancer Sites with Decreased Risk for F&V Consumption(“Limited”)
Prevention of Cancer from Fruit and Vegetable Consumption • Assumptions for estimate: • Reasonable estimates for prevented cases can be estimated from the RRs from the WCRF/AICR meta-analysis • Estimate based on half of the population with least fruit and vegetable consumption increasing consumption by 1 serving each of fruits and vegetables (80 gram/day serving) • Avoided cases based on RRs and SEER background cancer rates. • To avoid overestimates, an average of fruit and vegetable estimates were used. • RR from lung cancer case-control was dropped as an outlier
Estimation of Cancer Risks • Steps: • Assemble PDP data from 2004-2008. • Identify pesticides with cancer unit risk estimates from EPA (21) (OPP and IRIS estimates) • Used consumption data from the CSFII (94-96, 98). Use surrogates to account for all food items. Estimate average exposure (assume as lifetime exposure). • Apply standard cancer risk assessment methods to estimate total cancer risk for pesticides in the diet (i.e., Risk = Exposure X Q1*) • Adjust to 80 gram serving each of fruits and vegetables. • Current U.S. population assumed as 310 million
Cancer Risk Benefit Analysis for Fruit and Vegetable Consumption (Annualized)
Chemicals Contributing to Cancer Cases for Vegetable Consumption
Uncertainties – Cancer Benefit Estimates • Strengths of epidemiologic data: • Based on humans! • Lots of different studies • Central estimates of risk • Includes pesticide risk (essentially a net benefit) • Weaknesses of epidemiologic data: • Confounding is always a concern • Consumption estimates are uncertain • Some researchers think the cumulative evidence is weaker than “probable” (Key, 2011)
Uncertainties – Cancer Benefit Estimates • Confirming evidence • Mechanistic evidence for components of F&V including carotenoids, lycopene, folic acid, and Vitamin C (tumor initiation and progression). • Boffetta et al. (2010) study of European population found similar estimates
Uncertainties – Cancer Risk Estimates • Risk based on EPA cancer unit risk factors: • Based on high dose rodent bioassays. • Use an extrapolation method to estimate risk at lower, untested doses. • For example, lowest dose in permethrin study was 3 mg/kg/day, whereas average exposure was 1.3x10-4 mg/kg/day (20,000-fold difference) • EPA on its cancer risk estimates: “while uncertain, are more likely to overstate than understate hazard and/or risk.”
Uncertainties – Cancer Risk Estimates • Criticisms of rodent bioassays (Ames and colleagues): • High doses lead to chronic wounding of tissues, cell death, and chronic cell division of neighboring cells to replace damaged tissue. • Causes cancer at high doses that would not occur at lower doses. • 99.9% of pesticides in the diet are from natural sources • Of the small number of natural plant pesticides that have been tested with rodents, half are positive.
Diuron Cancer Bioassay vs. Exposure Average exposure ~ 2x10-9 mg/kg/day
Uncertainties – Cancer Risk Estimates • Evidence contrary to carcinogen classification for dieldrin: • Study of 570 workers at a production plant from 1954-1970 (Van Amelsvoort et al., 2009). • No elevation of cancer incidence. • Results not consistent with Q1* (Sielken et al., 1999) • No association with cancer and organochlorine exposure in the Agricultural Health Study (Purdue et al., 2007).
Uncertainties – Cancer Risk Estimates • Potential sources of underestimation: • Non-detect residues were counted as zero • No practical way to do otherwise • Some pesticides are considered “possible” carcinogens and do not have Q1* values – these were not included • Counterbalanced by not including F&V-cancer associations with “limited” evidence.
Conclusions • Benefits of eating fruits and vegetable far outweighs any potential risks from pesticide residues • For cancer residue effects are 1/2000th, at most, for prevention benefits • Risk estimates for residues are likely overestimated • Estimates are strongest on a comparative basis. • Substantially more attention is given to the pesticide residue effects than on the benefits • Public health would be served by this perception changing.