The results are in: glyphosate and glyphosate products cause cancer. Health Canada must address these new scientific findings by August 18, 2025, because of a recent Federal Court case.
The Ramazzini Global Glyphosate Study (GGS)
The long-awaited study, Carcinogenic effects of long-term exposure from prenatal life to glyphosate and glyphosate-based herbicides in Sprague-Dawley rats, was published on June 10, 2025, in Environmental Health. The 26-month, long-term study of carcinogenicity on rats found that exposure to glyphosate and glyphosate based herbicides at doses equivalent to the acceptable daily intake (ADI) for Europe caused statistically significant, dose-related increased trends or incidences of:
multiple benign and malignant tumors of blood, skin, liver, thyroid, nervous system, ovary, mammary gland, kidney, urinary bladder, bone, endocrine pancreas, and circulatory system.
…early onset and early mortality for a number of rare malignant tumors, including leukemia, liver, ovary, and nervous system tumors.
In its release, the Ramazzini Insitute indicated:
“the GGS is the most comprehensive toxicological study ever conducted on glyphosate and glyphosate-based herbicides.” A co-author indicated, “This new evidence has to be carefully considered by the regulatory authorities globally.”
The study provides clear evidence that the findings of Health Canada’s Pest Management Regulatory Agency (PMRA) and the U.S. Environmental Protection Agency (EPA) are wrong. Both agencies found that glyphosate is unlikely to cause cancer.
PMRA Must Address the Global Glyphosate Study
In our recent February 18, 2025 legal win concerning the renewal of a glyphosate product, the Federal Court of Canada ordered PMRA to “redetermine the renewal [of the product] within six months of this decision [being August 18, 2025], in accordance with these Reasons.” At issue was the assessment conducted by PRMA at the time of a product renewal, and in argument, PMRA said it relied on the prior 2017 substantive risks assessment and looked at new information provided to it in a letter from Ecojustice on behalf of us and other applicants. But PMRA could not prove it had looked at the new information.
The Federal Court’s Reasons describe the times for products renewal “as streamlined yet still substantive ‘pulse checks’ that use newly available information to reassess the risk level of registered products up for renewal.” The Court adopted PMRA’s interpretation set out in its PowerPoint presentation The Proposed Integrated Approach to Pesticide Evaluation, which sees renewal times “as a pulse check [to] consider information throughout the pesticide lifecycle” to determine if there are “any emerging risk issues that require review.” The PowerPoint shows a review of the risk assessment on file to “consider new information available.”
It is our view that the GGS provides newly available information to PMRA which, based on the Reasons, must be considered when PMRA redetermines the renewal of the glyphosate product, due by August 18, 2025.
Health Canada Dismissed Cancer Evidence in Its 2017 Re-Evaluation
The last substantive risk assessment of glyphosate was set out in the Proposed Re-evaluation Decision PRVD2015-01, which formed the basis for the decision in Re-evaluation Decision RVD2017-01 to continue the registration of glyphosate in Canada. The documents show PMRA saw evidence of cancer in rodents back in 2015, but decided to NOT conduct a substantive cancer risk assessment:
- PMRA found “equivocal” (uncertain) evidence of cancer in a rodent study, the Atkinson mouse study, but dismissed it. The study is described in the Proposed Re-evaluation Decision PRVD2015-01., (PMRA# 1161786, 1161795: 1993, Glyphosate 104 week dietary carcinogenicity study in mice, PRVD p.79).
- This study is discussed by PMRA’s reviewer in a Glyphosate Toxicology File, which provided the toxicology assessment for PRVD2015-01. The reviewer looked at the findings of the Joint Meeting on Pesticide Residues on the study, and stated (p. 89 of Glyphosate Toxicology File):
It is noted that there was a slight increase in the number of animals in the high-dose group of both sexes having multiple tumour types, which led to an overall increase in the total number of tumours in these groups. Due to the lack of histological [microscopic] evidence [of] an increase in incidence in any tumour type, and because the high dose was the limit dose of testing and would be irrelevant to chronic human exposure scenario, this finding was not considered a sign of carcinogenic potential of glyphosate.
- PMRA ported this reasoning as an excuse to not conduct a substantive cancer risk assessment (PRVD p. 91, 92). It called the tumours “benign” and occurring at the high dose: “Low level of concern due to benign nature of tumours observed at the limit dose and lack of oncogenicity in other studies.”
- Further, an Access to Information request (discussed below) revealed that PMRA was aware of and on had on file the 1985 BioDynamics 24-month study on CD-1 mice, and the EPA memo concluding that glyphoste caused tumors: “Glyphosate is oncogenic in male mice causing renal tubule adenomas, a rare tumor, in a dose-related manner”. A consensus review by a committee of the Toxicology Branch of the EPA agreed, and classified glyphosate as a Category C oncogen (possible human carcinogen). A letter on file from Monsanto disputing this finding was rejected by the committee. Yet PMRA did not include this study in its database for chronic toxicity/oncogenicity.
Arguments Not Justified: See U.S. 9th Circuit Court of Appeals
The excuse provided by PMRA in the PRVD2015-01 for not conducting a cancer risk assessment – benign tumours at limit dose – is not justifiable.
- First, the Toxicology File did not call the tumours benign. It said there was no microscopic evidence of advancement to cancer.
- Regardless, the fact that a tumour is benign is not a justification for not assessing it. The fact that a tumour is benign is a sign that it may produce tumours in humans; plus the significance of such a tumour is increased if other factors are present, such as multiple tumour sites (as was the case in the Atkinson mouse study) (EPA’s Guidelines for Carcinogen Risk Assessment Section 2.2.2.1.4).
- The “limit dose” argument has been dismissed as unscientific by the United States 9th Circuit Court of Appeals, in its 2022 decision concerning the preliminary cancer assessment conducted by the EPA.
- The EPA argued that glyphosate studies that showed tumors were in instances where treatment with glyphosate occurred at “high doses,” and that these were “not considered relevant to human risk assessment” because potential exposure of humans was “well below the doses necessary to elicit the effects in these animal carcinogenicity and genotoxicity studies” (Decision p.29)
- The Court held that this argument conflicted with EPA’s own Cancer Guidelines: that “no part of the hazard assessment Guidelines encourages disregarding results occurring at high-dosage ranges for any reason other than when there is evidence of excessive toxicity,” and that “[i]n general…effects seen at the highest dose tested are assumed to be appropriate for assessment.” Moreover, disregarding results at the high-dose range is contrary to the purpose of hazard assessment, which “is to construct a total analysis examining what the biological data reveal as a whole about carcinogenic effects and mode of action of the agent, and their implications for human hazard and dose-response evaluation.”
Because of the 9th Circuit Court of Appeal’s decision, the EPA withdrew its entire Interim Registration Decision on glyphosate. This means there is no current registration decision in place for glyphosate in the United States.
Access to Information Shows the EPA and PMRA Assessments Were Joint
So why has PMRA not revisited its cancer conclusion since EPA’s is vacated?
The PMRA and EPA worked hand-in-glove on their assessments of glyphosate, as shown below. Since the assessment of the EPA has been vacated by the Courts as unscientific, the question arises as to why PMRA has not examined its re-evaluation (and conclusion that glyphosate is not likely to cause cancer) in light of the 9th Circuit Court of Appeal Decision? Throughout PRVD2015-01 and RVD2017-01, and in court cases, PRMA has stated its conclusions are “consistent with all other pesticide regulatory authorities world-wide” (PRVD2015-01 p. 15). In RVD2017-01 (p.17), PMRA even says:
The PMRA is continuing to monitor regulatory activities from other regulatory organizations, including the U.S. EPA’s review of the SAP recommendations and final determination regarding the potential carcinogenicity of glyphosate.
The question remains unanswered.
Access to Information Evidence of Joint Review of Glyphosate
PMRA published a document in 2010, Re-evaluation Work Plan for Glyphosate (REV2010-02), indicating it would be working “cooperatively” with the EPA on the re-evaluation of glyphosate. A March 2025 response to an Access to Information Act request shows just how closely the two agencies worked together.
The Release Package A-2022-000827 provided documents from 2008 to 2022 concerning the joint or coordinated or cooperative review of glyphosate between the agencies. It shows, among other things, that they shared the same science, had the same timelines, reviewed and commented on each other’s work, and met to discuss issues of disagreement. Their science base for health risks was extremely limited. They also jointly met with the registrants:
- The 2 agencies created Joint Review workplans, which assigned each agency specific tasks. Each agency would “conduct a primary review of data for which they have been assigned”. Issues and clarifications were discussed. Secondary, peer reviewers would then provide comments on the data evaluation records (DERs).
- The workplan contemplated there being “no outstanding issues” between the agencies, and also telling the registrant/applicant (the pesticide company) about outstanding issues so that they could be addressed:
E-mails or conference calls will be used as appropriate to discuss issues/points of disagreement pertaining to the integration of the secondary review comments into the DERs.
Note: Outstanding issues that must be addressed by the applicant should be communicated to the applicant by the administrative lead.
At the end of the Secondary Review Stage, the project lead will organize a call to ensure all secondary reviews have been completed and there are no outstanding issues. - The workplans indicated that each agency would “conduct independent risk assessments” and “may share them with each other as completed.” In fact, the risk assessments were shared with each other, and comments were provided on drafts, before completion. This is confirmed by the briefing notes for the September 11, 2014, Science Management Committee meeting of the management committee of PMRA in which the committee reviewed the assessments for purposes of making a decision. The briefing states:
“The Agencies are each preparing separate risk assessments which are shared for information.”
- The Joint Glyphosate Task Force, the industry organization formed to deal with the re-evaluations, attended meetings and engaged in communications with the EPA and PMRA on the re-evaluations.
- PMRA’s last assessment was from 1991 (Discussion Document 91-01, Decision Document 1992-02).
- The second document in the Release is the BioDynamics 1985 memo and review by EPA on the 24 month oncogenicity study on CD-1 mice, with results showing glyphosate caused tumors, supporting a “possible human carcinogen” conclusion. An attached letter from Monsanto was redacted, but the committee notes of the Toxicology Branch of EPA’s Office of Pesticides and Toxic Substances clearly disagreed with the registrants (Monsanto’s) position.
- Notes in the Release indicate the agencies thought new assessments would be required if the endpoints for toxicology, the safety levels changed based on the science. The endpoints changed, but there is no evidence new assessments were conducted.
- All that happened was that a PMRA reviewer conducted an open literature review in 2012, by performing internet searches. Almost all were rejected:
- The focus of the search was on toxicology endpoints, not on the exposure side of the risk equation Risk=Hazard x Exposure. In other words, searches ignored large components of risk assessment.
- The search brought up 62 studies, then after 2012 it appears 18 more were found. The PMRA reviewer(s) then reviewed these studies for acceptability against the EPA’s Guidance for Considering and Using Open Literature Studies to Support Human Health Risk Assessment, which are very strict and exclusionary. All but eight were rejected for risk assessment purposes, and only two of these eight were useful for quantitative risk (endpoint) assessment purposes.
- The criteria for acceptance included: the article is presented as a full article (i.e., not abstract); the article is available in the English language; the paper is publicly available document; the paper is the primary source of the data, although some secondary [review papers] and regulatory reports were included; the location of the study is reported. We think that rejection based on such criteria does not constitute a “scientifically based approach.”
- The two studies that were “useful” were the National Toxicology Program (NTP) 90-day studies on rodents, impacting the salivary glands.
- PMRA noted the studies in PRVD2015-01 p. 12 and 47, but dismissed their significance. In the section on aggregate risk assessment, PMRA did indicate that effects on salivary glands “could potentially result from exposure to glyphosate via inhalation or dermal routes,” but when it realized it could not present relevant data to examine the issue, it resorted to an oral study.
- The EPA stated “none of these [NTP] studies were found to have a quantitative impact on the hazard characterization or preliminary human health risk assessment for glyphosate.”
Conclusion
PMRA’s assessment of glyphosate dismissed evidence of cancer for reasons that are not justified scientifically or in law. PMRA worked tightly with the EPA, and used the same argument to dismiss evidence of cancer that was used by the EPA. The Courts have forced the EPA to withdraw its decision, in part because of this unscientific argument, but PMRA has not revisited its cancer findings.
Now the Ramazzini GGS provides new evidence of cancer that can’t be ignored. PMRA must address this evidence no later than August 18, 2025, because of the recent Federal Court decision in Canada.
We hope that Canada’s new Minister of Health, the Honourable Marjorie Michel is aware of her primary mandate. She must have a reasonable certainty that no harm will arise to human health (and the environment) from the use of glyphosate. There can be no such certainty in the face of the Global Glyphosate Study.
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Safe Food Matters Inc. sued Health Canada’s PRMA over its 2017 assessment of glyphosate, and the case is ongoing. A decision on a minor preliminary motion is expected June 13, 2025, and then the schedule for the case can be set.
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