Does Atrazine Affect the Risk of Cancer? (PowerPoint Text)

Pesticide Applied Learning Series (PALS)
  • Snedeker, Suzanne
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Translational cancer research – expanding your knowledge

  • Do environmental chemicals affect the risk of cancer?
  • 1995 Cornell University Program on Breast Cancer and Environmental Risk Factors was founded to address these concerns
  • Launched a new translational research program
  • Address the relationships between environmental factors and cancer risk
  • Critically evaluate the current scientific evidence
  • Translate this science-based data into information individuals can use to expand their knowledge and reduce their risk of cancer
  • Recommend promising avenues of new research
Breast cancer statistics for the US – projections for the year 2002

New Cases in Women: 203,500
New Cases in Men: 1,500

* US estimates for 2002 from the American Cancer Society, Cancer Facts & Figures 2002

The puzzle of breast cancer
  • Very complex disease
  • No one single factor associated with causing the disease
  • Breast cancer develops over a long period of time, usually 10 to 30 years
The puzzle of breast cancer – how does breast cancer occur?
  • There are many steps
  • Occurs as a result of a cell accumulating changes in key genes that control the cell’s ability to divide, mature and die
  • The result is an abnormal cell that divides out of control and forms a tumor
  • As the tumor grows, it may invade surrounding or distant tissues
  • Cancer cells can break off from the primary tumor and travel to distant sites invading vital organs
  • Early detection is important

Risks related to breast cancer




Pesticides – potential for exposure



Pesticides and breast cancer risk – possible mechanisms
  • “Complete” carcinogen
  • Co-carcinogen / tumor promoter
  • Endocrine disruptor (Hormonally Active Agent)
    • Mimics other hormones
    • Affects formation or breakdown of other hormones
    • Supports the growth of a hormone-dependent tumor
    • EPA is developing tests to identify which pesticides are endocrine disruptors
Atrazine

Atrazine – usage

Most widely used herbicide in the US
  • First registered for use in 1959
  • Annual crop land usage
    • Up to 77.3 million lbs active ingredient
*Source: Asplein, 1999

Agricultural crops
  • Primary crops
    • Field and sweet corn, sorghum and sugarcane
  • Other crops
    • Winter wheat, guava and macadamia nuts
    • Hay for animal fodder
    • Fallow land
    • Christmas tree farms


Other weed control uses
  • Turf – golf courses, home lawn care (Southeastern US, St. Augustine and Bermuda grass)
  • Right-of-ways
Application rates vary
  • Field corn, 1 lb to 2.5 lbs per acre
  • Sugarcane, up to 10 lbs per acre
  • Turf*, 2.0 lbs or less per acre (* Southeastern US)
Atrazine – cancer risk in women

Breast cancer
Two “ecological” studies from Kentucky
  • Study #1: higher rate of breast cancer in counties with:
    • Higher use of corn herbicides
    • Higher levels of triazine herbicides in water supplies
    • Study criticized because of crude methods used to estimate atrazine exposures
  • Study #2, a 5-year follow-up study:
    • Breast cancer risk not associated with
      • Acres of corn planted
      • Atrazine sales
      • Atrazine levels in water supplies
    • But, study did not measure skin exposures, drift, or levels inside farm homes
Atrazine – cancer risk in lab animals

Breast Cancer
  • Increased number or earlier appearance of mammary (breast) tumors in one type of female rat
  • Not all types of laboratory animals are affected
  • No mammary tumors seen in other rat strains or in mice fed atrazine
  • Atrazine is not an estrogen mimic
  • May disrupt other hormonal pathways that affect mammary cancer in rats
    • Decreases luteinizing hormone
    • Increases prolactin levels
  • These two hormonal pathways may not be as important in human breast cancer
Atrazine – cancer risk in women

Ovarian cancer
  • Study of Italian women
  • Exposed to triazine herbicides
    • Atrazine and simazine
  • Risk of ovarian cancer higher in exposed women
Stomach cancer
  • Emerging area of research
  • Study in Ontario, Canada
    • Higher rates of stomach cancer seen in areas with higher levels of atrazine in the drinking water
Non-Hodgkin’s lymphoma (NHL)
  • Inconsistent results in studies of Midwestern male farmers
    • Studies in Iowa, Minnesota, and Ontario, Canada did not see a higher risk of NHL
    • Studies in Nebraska and Kansas saw higher risk of NHL
    • When they controlled for other pesticides (e.g. 2,4-D), atrazine-effect not as strong
Atrazine – EPA’s cancer risk assessment
  • 1988
    • EPA rated atrazine as a ‘possible human carcinogen’
  • 1994
    • EPA placed atrazine under “Special Review”
  • December 1999
    • EPA’s preliminary cancer risk assessment, rated as ‘probable human carcinogen’
  • 2000
    • Scientific Advisory Panel (SAP) did not agree with EPA draft report
    • New research on relevancy of rat data available
    • Atrazine caused reproductive changes in one strain of rats that influenced levels of hormones important in rat mammary (breast) cancer
    • These reproductive changes seen in atrazine-treated rats probably would not occur in women
    • SAP concluded that it is unlikely that atrazine would affect human breast cancer risk
  • June 2000
    • Based on SAP recommendations the EPA changed atrazine’s cancer classification to: “not likely to be a carcinogen in humans”
  • EPA’s reregistration decision expected in 2003
Atrazine – effects on wildlife
  • Sexual development in frogs
    • Atrazine may increase levels of an enzyme called aromatase
    • This enzyme converts testosterone to estrogen
    • Would explain why blood levels of testosterone in atrazine-treated male frogs are so low
    • More research is needed to confirm this “aromatase” hypothesis
  • Male tadpoles exposed to atrazine
    • All had abnormal sexual development
    • Up to 20% had both testes and ovaries
    • Males were more like females
    • Occurred at very low levels of atrazine
    • Adult frogs had low levels of the male hormone testosterone
Atrazine – effects on aromatase
  • Are levels of the aromatase enzyme or sex hormones changed in humans exposed to atrazine?
    • Not known
Atrazine & its breakdown products – exposures of concern
  • Workplace exposures:
    • Handling, mixing, loading or applying to row crops or right-of-ways
    • Post-application field work (sugarcane)
    • Aerial application or hand spraying
    • Turf application
      • Use of “belly grinders”
      • Proper protective clothing is needed when applying atrazine to treat turf in playgrounds, golf courses and residential lawns.
  • Rural families
    • Drift from treated fields
    • Tracking into homes
    • Tracking into living & food preparation areas
    • Handling soiled work clothes
    • Drinking water from contaminated wells or contaminated community water supplies
Atrazine levels in water supplies – trends

1980s
  • Frequent detection of atrazine in groundwater and surface water
  • Levels greater than the EPA ‘Maximum Contaminant Level’ (MCL) of 3 g/L
  • Levels detected exceeded 20 mg/L
  • Surface water levels – influenced by surface run-off from spring rains after application
1990-2000s
  • Still see high frequency of detection
  • Now have very sensitive methods
  • Analytical ability to detect atrazine has improved
  • However, levels are lower, usually below MCL allowed in drinking water
  • But, there is concern that in some agricultural areas, still see atrazine levels exceeding the MCL
Atrazine & its breakdown products – exposures of concern
  • Residential - Recreational Exposure
    • Adults
      • Mixing and applying atrazine to turf
      • Contact with treated turf; residential lawns, mowing, golf courses and parks
      • Tracking into living & food preparation areas
    • Children
      • Playing on treated turf at home, playgrounds and parks
      • Hand to mouth behavior, and dirt eating
Atrazine and cancer risk – the unanswered questions
  • Is the risk of breast or ovarian cancer increased in women?
  • Is the risk of stomach cancer or Non-Hodgkin’s lymphoma (NHL) increased in men?
  • Do low levels of atrazine have an impact on wildlife ecology and declining amphibian populations?
  • Does atrazine increase levels of the aromatase enzyme and affect sex hormone levels in humans?
  • What are the trends in levels of atrazine and its breakdown products in surface water, rural drinking water wells and rainfall?
  • Can atrazine breakdown products affect human health?
  • Can exposure to atrazine affect sensitive populations such as children or developing wildlife?
Pesticides and health outcomes – emerging research

Agricultural Health Study
  • Evaluating whether exposure to agrochemicals affects the health of farm families
  • Ten-year study sponsored by the National Institutes of Health
  • Includes 57,000 men and 32,000 women from farm families in Iowa and North Carolina
  • Health endpoints to be evaluated
    • Breast and Prostate Cancer
    • Parkinson’s disease
    • Thyroid disease
    • Reproduction
    • Asthma
    • Osteoperosis
    • Childhood diabetes
      For more information http://www.aghealth.org
Summary
  • Breast cancer is a complex disease and environmental factors may play a role in determining its risk
  • Atrazine is widely used in agriculture for crop protection especially for corn, sorghum, sugarcane, and hay crops, and on turf in the Southeastern US
  • Atrazine causes mammary tumors in some types of laboratory animals\
  • We do not have strong evidence that atrazine affects the risk of cancer in humans
  • The EPA has concluded atrazine is not a human carcinogen
  • Low levels of atrazine in water can cause harmful effects on the sexual development of frogs
  • There are exposures of concern to atrazine in both workplace and residential settings
  • Atrazine is widely detected at low levels in water supplies, and there is some concern that levels above drinking water standards persist in some agricultural areas
  • More research is needed to monitor levels in water supplies, determine human health risks including cancer risk, and effects on wildlife
Resources on Pesticides – http://envirocancer.cornell.edu
  • Cancer maps
  • Fact sheets on cancer risk and chemicals
  • Bibliographies on environmental risk factors
  • Searchable Bibliographic Database
  • Newsletter “The Ribbon”
  • Links to: Information on health effects of pesticides, policy and legislation, and new research studies
BCERF on the Web http://envirocancer.cornell.edu
Cornell University Program on Breast Cancer and Environmental Risk Factors in New York State (BCERF)

Acknowledgments - funding

This material is based upon work supported by Smith Lever funds from the Cooperative State Research, Education, and Extension Service, US Department of Agriculture and a grant from the New York State Departments of Health and Environmental Conservation.

Any opinions, findings, conclusions, or recommendations expressed in this module are those of the author and do not reflect the view of the grantors.

Acknowledgments - production & design

Graphics & Animation: Mari Stewart, Sean Gardner, Jason Hernandez
Narration: Mari Stewart
Guidebook Formatting: Neil Rotach, Carin Rundle, Mari Stewart

Disclaimer and Reproduction Information: Information in NASD does not represent NIOSH policy. Information included in NASD appears by permission of the author and/or copyright holder. More

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