Pesticides and their links to cancer

Pesticides and their links to cancer

Pesticide use has been linked to two thirds of all cancers; in both farmers and consumers, with breast cancer, prostate cancer, lymphoma, thyroid cancers and multiple myeloma leading the way.

Pesticides are designed to kill living organisms. Regulation limits concentrations and individual exposures. But multiple pesticides may be used in farming. And crops may be sprayed on multiple occasions. 

There are a number of different pesticide groups. Many of them are not just poisons, they are endocrine, or hormone, disrupters.

     * In a 2006 study, the effects of using two pesticides simultaneously had a multiplier effect -prothiofos/pyriproxyfen or thiabendazole/orthophenylphenol when used in combination produced a staggering 10-fold increase in oestrogen activity. And another study found supermarket strawberries had 23 pesticides present! 

     * Two insecticides Lindane and DDT have both been confirmed as carcinogens by IARC having been shown to cause lymphoma. DDT was also linked to testicular cancer and liver cancer, while IARC stated that Lindane increased lymphoma risk by 60 per cent.

     * A  2021 study by The Silent Spring Institute has shown that 296 chemicals found in pesticides, contaminated resources and consumer products could increase breast cancer risks via hormone level changes. The study was published in Environmental Health Perspectives (1).

Babies, children, pregnant women, the elderly and those with pre-existing medical problems are particularly vulnerable to the effects of pesticides.

As long ago as 12th July 2006 the European Commission stated that, "Long term exposure to pesticides can lead to serious disturbances to the immune system, sexual disorders, cancers, sterility, birth defects, damage to the nervous system and genetic damage. 

In the USA, the National Institute of Environmental Health Sciences (NIEHS) was set up in 1966 by Congress for the purpose of reducing human illness caused by hazardous substances in the environment. It is part of the NIH. From here comes the statement that 66% of all cancers have links to environmental toxins. Over 63 per cent of commonly used lawn pesticides and 70 per cent of school pesticides have links to cancer and many of these are endocrine disrupters according to the US National Cancer Institute (2).

'Beyond Pesticides' is an excellent resource in the USA for up to date information and research. For example a new meta-analysis by researchers from Claremont Graduate University has expanded on a 1998 study including two meta-analyses and found consistent results - pesticides can increase the risk of brain tumours in farm workers by 20 per cent. The comprehensive review is based on 42 years of data.

There is a 2014 IARC publication written by Dr Dana Loomis which talks of how IARC, the International Research agency in Lyon has evaluated over 950 compounds since 1971, of which 114 are carcinogenic to humans, with another 330 probably or possibly carcinogenic (3).

A 2011 review concluded that multiple pesticide exposures increase lymphoma risk amongst farmers (4) and, of course, there are multiple law suites from farmers against Monsanto, (now Bayer) over the herbicide Glyphosate.

In 2021 there was a review of pesticide use by male farm works which linked higher risk of Thyroid cancer (5). Metalaxyl and Lindane were the worst culprits.

In a report in 1990 entitled Pesticides, Chemicals and Health, the British Medical Association (BMA) detailed studies that had linked pesticide use and various forms of cancer among farmers, including prostate cancer, lymphoma, multiple myeloma, leukaemia and soft tissue sarcomas.

Many studies have also linked pesticides to non-occupationally exposed groups such as rural residents and communities living near regularly sprayed fields. One US study found high brain cancer rates in people living near cranberry agricultural fields in Cape Cod, Massachusetts. Results showed that living within 2,600 feet of the cranberry growing area resulted in twice the risk for all brain cancers and nearly a 7-fold increased risk for a type of brain cancer known as astrocytoma (6).

For prostate cancer, few pesticides played a role according to a 2020 analysis by the National Cancer Institute. However, one, the organodithoate insecticide, 'Dimethoate' was linked to aggressive prostate cancer in 'ever users', over never users (7). 

Although there seems to be some link to Childhood Leukemia from pesticide exposure, the strongest links exist between maternal pesticide exposure during pregnancy and childhood, AML, followed by ALL (8).  In a second study, repeated exposure to pesticides amongst farmer was linked to leukaemia, and especially their children (9).

Go to: Cancer risk in the workplace

References

1. In vitro assay of chemicals that increaseestradiol and are potential Breast cancer risks;Bethsaida Cardona and Ruthann A. Rudel, Silent Spring Institute

2. Beyond Pesticides 2021

3. 2014 IARC report Dana Loomis PhD.

4. Tina Kaczor - Multiple Pesticide Exposures increase lymphoma risk

5. Pesticide exposure and incident thyroid cancer - Environment International Jan 2021 Volume 146

6. Aschengrau A, Ozonoff D, Coogan P et al. Cancer Risk and Residential Proximity to Cranberry Cultivation in Massachusetts. American Journal of Public Health, 86(9): 1289-1296. 1996.

7. Pesticide exposure and risk of aggressive prostate cancer; Environ Health, 2020 March 5; 19(1). Larissa A Pardo et al.

8. Exposure to pesticides and childhood leukemia risk; Maria A. Karalexi et al; Environ Pollut, 2021 Sept 15, 285

9. Asia J Cancer; Zakerinia Maryam et al 2015;  https://pubmed.ncbi.nlm.nih.gov/25640359/

2021 Research
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