The Coalition for a Healthy Ottawa


For CCHE's analysis of the PMRA's 2,4-D review, please click here

Updated: April 2007

Originally written: March 11, 2005

Highlights of Major Problems with PMRA's Feb. 21, 2005 Review on 2,4-D Herbicide

On Monday, February 21, 2005, the Pest Management Regulatory Agency (PMRA) made an interim announcement that the pesticide 2,4-D can be used safely on lawns and turf when label directions are followed. The PMRA is a federal body responsible for the regulation of pesticides in Canada, within Health Canada. 2,4-D is the most common weed-killer used on lawns, and is one of the pesticide active ingredients to be banned from use on all green spaces across the Province of Quebec.

The public has until Earth Day (April 22), to comment on this proposal. It may be accessed online
here. The PMRA is failing to protect health of Canadians on their home turf. Here are some of the shortcomings:Up

Toxicity of Chemicals
The PMRA relied upon animal studies, generally with rats. In April 2004 the genome of the rat was published in the prestigious journal "Nature". An important finding was that rats have genes that do not exist in people for detoxification of chemicals, and therefore are a poor model for toxicity testing. (There is a reason that rats can live in sewers and garbage dumps, and people cannot.) Dogs are much more sensitive to 2,4-D, but the dog data was put aside in favour of the more robust rats.

Pesticides are the only chemicals deliberately made toxic, and spread in the environment for that effect. All life shares common biochemical pathways and structures, so pesticides are, in some way, toxic to all species.

2,4-D comes as various salts and esters. The diethanolamine salt is particularly toxic, and was explicitly excluded from the review, but the DEA form is in many herbicide and "weed and feed" type products.

2,4-D for lawn care is usually mixed with other pesticides (namely mecoprop and dicamba), and always with other ingredients. The toxicities of mixtures were not considered. Many products containing 2,4-D contain racemic mecoprop, that is being withdrawn by the manufacturer, but may be sold until 2009.

Fertilizer-herbicide mixtures ("weed and feed" - type products) should be banned for many reasons (
see factsheet on Weed and Feed).Up

Label Directions
Children, pets and wildlife don't read signs to keep off the grass, and research shows that people don't follow strict, detailed instructions as to how to spray (quantities, weather restrictions, buffer zones). Neither do they avoid contact with skin, eyes, inhalation etc (wear protective clothing, chemical mask, gloves etc). Even if they did, the PMRA has now restricted the frequency of application and the allowable application rate, and added buffer zones, so users have not been and will not use the pesticide "safely", presumably, until this has gone into effect.

The Ontario College of Family Physicians found the open, peer-reviewed literature regarding humans clear enough for our doctors to advise pesticide avoidance if at all possible. Non-Hodgkin's lymphoma and leukemia are frequently noted in conjunction with herbicides, along with brain tumours and neuroblastoma (children). The PMRA, after lengthy discussion of whether our children more closely resemble dogs, rabbits or rats, preferred to rely upon secret animal studies supplied by the industry, that do not demonstrate carcinogenicity, and in the end was undecided over whether or not 2,4-D caused cancer.

The "independent Science Advisory Panel" noted that childhood cancer did merit more study. The PMRA said that this was a difficult area of study, and preferred to rely upon animal toxicity data. Of course, if there was a reliable correlation between animal and human cancers, the disease would have been cured years ago.

Reproductive Difficulties
A reproductive study required by the PMRA was still pending from the pesticide industry. 2,4-D has been found in semen, blood and urine, and has been linked in the open literature to difficulties conceiving and bearing children and to gender imbalances. An animal study demonstrating failure of pregnancy using "off-the-shelf" herbicide was rapidly and vigorously attacked by the pesticide industry, but no retraction was ever published.

Neurological Impairment
The PMRA had not received from the pesticide industry a required developmental neurotoxicity study.  The possibility of neurological impairment is noted on the label for professional applicators: "2,4-D may cause severe irritation to the eyes. Prolonged breathing of 2,4-D may cause coughing, burning, dizziness or temporary loss of muscle coordination. Other possible effects include fatigue, muscle weakness or nausea. Treat symptomatically."  Homeowners will not be so warned.

UPDATE: The PMRA has placed a condition of registration on 2,4-D such that the 2,4-D registrant(s) must provide the PMRA with a required developmental neurotoxicity study by September 20, 2009.

The PMRA report was published before the required dioxin analyses had been provided by the Industry Task Force II on 2,4-D Research. Dioxin contamination has been problematic in the past, but since 1983 the federal government has been assured by the manufacturers that it is no longer a problem and no further monitoring has been carried out.

Chlorinated dioxins are inevitably formed during phenoxy herbicide manufacturing (2,4-D, mecoprop and dicamba are all phenoxy herbicides used in mixtures on turf). "Dioxins" is a large group of chemicals that persist in the environment, and that may cause cancer, harm neurological development, impair reproduction, disrupt the endocrine system and alter immune function. An industry lobbyist admitted that when the reactor gets too hot (conditions favouring dioxin formation) the batch gets pulled.

Under Canada's Environmental Protection Act, dioxins with more than 2 chlorine atoms are targeted for virtual elimination. Dioxins with 2 and 3 chlorines will be the predominant contaminants in 2,4-D, although some higher-chlorinated forms will be more minor contaminants. However, the PMRA is only asking for analyses of dioxins with 4 or more chlorines. Thus, the PMRA is in contravention of the CEPA. It is also asking for an experiment to be conducted that will ignore the bulk of the problem. Moreover, the pending analyses will be carried out on five samples picked by the industry (low-temperature samples with little contamination will doubtless be chosen) and analysed for the industry. Surely unfavourable results will be discarded. In Canada there is no monitoring of contamination of commercial products or of herbicide-related dioxins in the environment (e.g. in sediments in waterways adjacent to golf courses).

Dioxin contamination may be an important contributing factor in inconsistent epidemiological evidence regarding herbicides and a wide variety of maladies.

Breakdown Products
A springtime stench blankets urban communities without bylaws or a Pesticide Code, and sickens people in stores where lawn pesticides are sold. This is principally the smell of the first break-down product of 2,4-D. 2,4-dichlorophenol is a very toxic chemical, but break-down products are not assessed in the review of 2,4-D.

Scientific Process
Serious problems with pharmaceutical trials and federal drug approvals have received considerable attention. Efforts to improve accountability and transparency include trial registration, standards for trial design, reporting and systematic review that are now required by medical journals. No such checks are in place for pesticides. Problems include: industry-provided, secret studies that are not open for peer review, reliance upon reviews by interested parties rather than systematic reviews of primary literature, and even reliance upon unethical studies such as human ingestion of 2,4-D. Canada does not track pesticide sales or use, and has no adverse effects reporting system.

Ultimately, science cannot define an "acceptable risk". It may illuminate risks, but the degree of acceptability is a decision for society. Rather than illuminating risks, the PMRA has been derelict in its duty to compile relevant information and to weigh it dispassionately. The most charitable conclusion might be that the report was premature, since all relevant data was not in hand. However, this proposal document flouts the CEPA and does not even approach scientific standards for medical research, to ensure truth and transparency. The PACR2005-01 should be grounds for major changes within the PMRA and Canada's regulatory regime for toxic chemicals. It is certainly grounds for cosmetic pesticide bylaws, and for Quebec to maintain its Pesticide Code, for the health of its people and as a fine example for the rest of the Canada and the world.

It is up to the people of Canada to tell the PMRA, and their politicians, how much uncertainty and risk are acceptable for the sake of killing dandelions in grass.

Prepared by Meg Sears (MEng, PhD)
For the Coalition for a Healthy Ottawa

To view the Canadian Coalition for Health and Environment (CCHE)'s Submission to the PMRA's 2,4-d re-evaluation please click here



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Last updated: April 30, 2007

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