After a three-year review, the Pest Management Regulatory Agency has again approved the use of the herbicide 2,4-D.
Developed after the Second World War, the safety of the weed killer has been upheld in numerous reviews in Canada and elsewhere, despite repeated attacks on its use.
PMRA will collect public comments on its decision until mid-April and then issue a special review document further explaining the science behind its decision.
PMRA noted 2,4-D-containing products do not present unacceptable risks to human health and the environment when used according to the label. There are some label restrictions on the number of applications and rules around buffer zones added after past re-evaluations.
As part of its decision, the PMRA said it assessed a report released last year by the International Agency for Research on Cancer (IARC), which classified 2,4-D as possibly carcinogenic to humans.
“The IARC hazard classifications are not health risk assessments and the levels of human exposure, which determine the actual risk, are not taken into account in the IARC assessments,” PMRA concluded.
The PMRA report also noted there are no incident reports of cancer related to 2,4-D use in the Canadian database it maintains. It also noted in the cancer cases that were reported by IARC, no clear link had been drawn and many other potential risk factors were present. At the same time the weight of evidence from animal studies that were designed to test causality did not support the finding 2,4-D has a causative effect, which caused the PMRA to conclude it cannot be classified as a human carcinogen.
“The PMRA’s assessment of the scientific data base is another consistent regulatory decision that concludes the use of 2,4-D not only protects food production but also the environment,” said Jim Gray, executive director of a crop protection industry task force formed around the emerging debate over 2,4-D and research data.
He said PMRA findings were consistent with expert reviews and earlier decisions of authorities such as the World Health Organization, U.S. Environmental Protection Agency, European Commission, and European Food Safety Authority.
In last two decades, PMRA has released four re-evaluation decisions on 2,4-D, all upholding its use in agriculture, forestry and turf management. In them they evaluated available scientific information related to the aspects of concern for human health and the environment, Gray said.
Gray also said a study in 2006 by RIAS Inc. concluded that 2,4-D and comparable herbicides save farmers $227 million in production costs or crop losses.
“Most notably, 2,4-D has long been recognized as being a superior tank-mixing partner with other herbicides, and that after seven decades of use, 2,4-D continues to show little evidence of weeds developing resistance to it,” he said.
The herbicide is approved for use in more than 100 other countries including the United States and Europe.