Acting on concern that the herbicide cyanazine may be a possible human carcinogen, the US Environmental Protection Agency (EPA) and manufacturers DuPont agreed in August to phase out production in the US over the next four years(1). The EPA also proposes to cancel most uses of dichlorvos because of a risk of cancer from dietary exposure(2).
Cyanazine
The EPA began a
special review of triazine herbicides-atrazine, simazine and cyanazine -in
November 1994, concerned that long-term exposure in food and drinking water may
pose a risk of cancer. EPA classifies these as 'possible human carcinogens'.
Over 16,000 tonnes of cyanazine are used annually in the US mainly on cotton,
maize and sorghum, making it one of the five most common pesticides.
Manufacturer DuPont says that for commercial reasons it will not support further
US registration, and will concentrate on newer active ingredients(3).
In the UK cyanazine is registered by Cyanamid for use in cereals, oilseed rape,
maize, linseed, and some vegetables. Usage is relatively low, 36.54 tonnes in
1994(4). Cyanazine is not scheduled for review by the UK Advisory Committee on
Pesticides (ACP). Nor is it among the European Commission's active ingredients
scheduled for priority review. Cyanamid UK expressed confidence in the product
and has no current plans to provide further data to demonstrate safety.
In 1993, the ACP reviewed atrazine and simazine, and concluded that the increase
in mammary tumours of female rats was of 'doubtful significance' for
humans-the strains of rats used for testing may have been prone to tumours.
Ongoing studies may clarify this area.
Dichlorvos
Dichlorvos was
registered in 1948 as an insecticide for fleas, livestock, premises and home use
(see PN 29, p.20). Following its special review, the EPA will cancel most
dichlorvos uses to eliminate unacceptable health risks to the public and
workers. Most retained uses will be restricted to trained certified applicators.
It poses a cancer risk through dietary exposure; a risk to the central nervous
system (cholinesterase inhibition); and a risk to those working with it or
entering treated enclosed areas.
The International Agency for Research on Cancer classes dichlorvos as possibly
carcinogenic to humans. The ACP, following its review of non-agricultural uses,
says "the weight of evidence presented does not suggest that dichlorvos is
a carcinogenic risk for humans."
Agreeing causes of cancer
In the light of the EPA concerns the
Pesticides Trust [now PAN UK] has asked the ACP for assurances that:
adequate data exist on cyanazine and dichlorvos that confirm neither is regarded as a human carcinogen; or that both will be subject to an immediate review;
an assessment of the likely implications for exposure via residues in food-particularly for dichlorvos-for UK consumers.
1. EPA press
release 2 August 1995.
2. EPA press
release 28 September 1995.
3. Agrow 238, 11
August 1995.
4. Arable Farm Crops in Great Britain 1994,
Pesticide Usage Survey Report 127, MAFF, London.
[This
article first appeared in Pesticides News No. 30,
December 1995, page 21]