When the World Health Organization’s International Agency for Research on Cancer released its “evaluation of five organophosphate insecticides and herbicides” study at the end of last month, they gave us some news we’re probably not too surprised to hear: Maybe agricultural chemicals cause cancer. But when researchers from the University of Canterbury and elsewhere released the results of a study they did on chemical herbicides’ affect on bacteria, they did deliver what might be a surprise: The chemicals can promote antibiotic resistance in bacteria.
First, Cancer
The IARC study looks at the herbicide glyphosate—the world’s most widely used herbicide and the active ingredient in RoundUp—as well as the pesticides malathion, diazinon, tetrachlorvinphos and parathion. Somehow, glyphosate is the only chemical to get media attention, whereas the study addresses important concerns for all of these chemicals. (And now having written this, I realize I’m focusing on glyphosate, too. But at least I’m mentioning the others … )
The IARC says:
- Glyphosate, malathion and diazinon are in the IARC’s Group 2A, sporting the “probably carcinogenic to humans” label. The IARC says this group shows “limited evidence” of carcinogenicity in humans—there’s association between exposure to the chemicals and cancer but other explanations can’t be ruled out—and “sufficient evidence” of carcinogenicity in experimental animals.
- There is limited evidence that glyphosate can contribute to the development of non-Hodgkin lymphoma in people and convincing evidence that glyphosate can cause cancer in laboratory animals.
- Glyphosate causes DNA and chromosomal damage to human cells.
- There is limited evidence of pesticide malathion’s link to non-Hodgkin lymphoma and prostate cancer in people. Malathion is used in agriculture, public health and residential insect control, and you could come in contact with it by residing near sprayed areas, during home use and by eating food contaminated with it.
- Malathion causes tumors in rodents.
- Malathion causes DNA and chromosomal damage and disrupts hormone pathways.
- For the pesticide diazinon, there was limited evidence of carcinogenicity in humans for non-Hodgkin lymphoma and lung cancer. Diazinon is used in agriculture and for control of home and garden insects, but use has decreased since 2006 because of restrictions in the U.S. and Europe.
- There is strong evidence that diazinon induces DNA or chromosomal damage.
- Tetrachlorvinphos and parathion are put in IARC’s Group 2B, so they’re “possibly carcinogenic” to humans. There is convincing evidence that these pesticides cause cancer in experimental animals but little or no information about whether it causes cancer in humans.
Next, Antibiotic-Resistant Bacteria
While the IARC let loose its ag-chemical news, an international team of researchers captained by New Zealand’s University of Canterbury also shared its unrelated findings that high-level exposure to common herbicides glyphosate, 2,4-D and dicamba can cause bacteria to exhibit resistance to the important antibiotics kanamycin and ciprofloxacin. In some cases, the study found the bacteria became more susceptible to the drugs, which is confusing, but the researchers say that in most cases, the bacteria were more resistant.
With antibiotic-resistant bacteria a topic that’s all the rage in the medical and agricultural fields, plus large-volume food buyers insisting on meat from chickens raised without antibiotics, this sure is interesting news. And by “interesting,” I mean it makes me want to go back to bed and not think about the crazy web of industrial agricultural that has been weaved for us.
Just Around the Corner
Monsanto, as you might imagine, isn’t thrilled with the IARC’s report, saying it’s biased and should be retracted. I couldn’t find reference to their reaction to the University of Canterbury study. In the meantime, the Environmental Protection Agency is conducting its own safety review of glyphosate as part of a regular 15-year monitoring and reregistration process that it conducts on all registered pesticides. (The IARC paper points out that the EPA originally classified glyphosate as “possibly carcinogenic to humans” in 1985 and reclassified the chemical as showing “evidence of non-carcinogenicity in humans” six years later, so we’ll see what this year’s report brings.) This is terrifying and fascinating stuff.
If Monsanto’s and EPA’s declarations of safety have been wrong all along and we really have been getting poisoned by them, what does that mean? Will everyone who has had one of these forms of cancer receive a bit of a sorry-for-the-hassle compensation, like Monsanto offered in its small-town-West Virginia remediation? If the EPA’s findings are in line with the IARC’s findings, this can be a game-changer for industrial agriculture. It’s possible, of course, that the chemical herbicides that will come in to replace glyphosate use will not be any better for us; but it’s also possible—fingers crossed here—that there will be a more-sustainable shift.
To keep the IARC report in perspective, check out clever video above by ag-, food- and environment-news group Grist (which I absolutely love) and the University of Michigan’s Risk Science Center that explains the IARC classification system and other everyday items that share IARC’s Group 2A and 2B designations with these ag chemicals.
