Vinclozolin

Vinclozolin is a fungicide introduced in the late 1970s. There are current concerns about reproductive toxicity, additive toxicity and potential endocrine disruption that have yet to be resolved.

What is vinclozolin?
Vinclozolin is a protectant non-systemic dicarboximide fungicide used mainly on oilseed rape and peas in the UK(1) and on vines, fruit and vegetables worldwide(2). It was first introduced by BASF in Germany in 1976 and is sold under a number of trade names including Ronilan and Flotilla.
    In 1998 23.4 tonnes were used on 80,574 ha of oilseed rape in the UK(3), and approximately 64 tonnes in total in the US(4) in 1999 on a wide variety of crops.

Acute toxicity
Vinclozolin is not acutely toxic, and is classified by the World Health Organisation as ‘unlikely to present acute hazard in normal use’(5). The acute oral LD50 (the dose required to kill half a population of laboratory animals) is more than 10,000 mg/kg for rats. It is an irritant to skin and may cause sensitization(6).

Chronic toxicity
A recent review of vinclozolin by the US Environmental Protection Agency (EPA)(7) has concluded that the chemical and/or its breakdown products are associated with the development of testicular tumours in rats, and the final breakdown product of vinclozolin in the rat is also thought to be carcinogenic. 
    Tests on dogs have shown effects on the renal and prostate glands. It is suggested they are the most sensitive species(8).

Reproductive toxicity
Issues over the reproductive toxicity of vinclozolin have driven regulation for over a decade. The UK Advisory Committee on Pesticides (ACP) has kept vinclozolin under review since 1991(9) following reports of the reproductive effects of the chemical on rats, to assess the risk to consumers and operators. The specific concerns were that vinclozolin could feminize rats and could also damage reproductive capacity in rats. Given that the chemical could be used by operators on a regular basis over quite considerable periods of time, and that a short exposure could have serious consequences for a ‘susceptible’ individual, and a high proportion of women were employed in the horticultural sector, action was needed.
    Approvals for use on strawberries, lettuce, tomato and raspberries were all suspended. Regulatory action was taken to reduce exposure to both by requiring tractor-mounted or trailed downward placement by hydraulic sprayer. Protective clothing requirements were also made. 
    Further data was submitted to the ACP in 1995, when uses in apple orchards were reinstated provided that the operator was protected by having air filtration fitted in the tractor cab(10).
    The European Union (EU) is currently reviewing the toxicity of vinclozolin.(11) In 1999, its Scientific Committee on Plants was asked to consider if humans and particularly children might be more sensitive than rats to its effects. The Committee said humans were not more sensitive than animals, and that it was unlikely that a single exposure could cause ill effects. It also considered that the mechanism of toxicity was now established. It did however, note that adverse effects on young animals were generally irreversible, whereas effects on adult animals could generally be reversed. It is likely that as a result the UK ACP will now consider restoring the currently suspended approvals.
    In the meantime, the US EPA considers vinclozolin to be an endocrine-disrupting chemical interfering with lipid metabolism and/or storage and inducing reduced sperm count, decreased prostate weight and delayed puberty in test animals.(12) A further question emerging from the EPA review is whether vinclozolin shares a common mechanism of toxicity with the fungicides procymidone and possibly iprodione, and what might be the likely impact of additive exposure.
    The European Commission(13) has also indicated vinclozolin as a high priority chemical for investigation of endocrine effects, and the UK Department of the Environment, Transport and the Regions (DETR)(14) has echoed these concerns.

Environmental fate
Vinclozolin is only partially broken down by soil microorganisms, with estimated half lives of three days to more than three weeks depending on soil type. Field data indicate it will be strongly sorbed to moist soils and unlikely to leach significantly(15).

Wildlife
There have been concerns about the possible impacts of vinclozolin on birds. The question was put to the EU’s Scientific Committee on Plants and received the answer that under the conditions of use of vinclozolin in orchards, vineyards and fields there would be no unacceptable risk to wild mammals.
    While short term effects on birds and wild mammals would not be expected, possible long term effects on birds could not be excluded(16).
    Vinclozolin is said to present a minimal hazard to bees when used as directed, but users are advised to ‘consider informing local bee-keepers if intending to spray crops in flower’(17). It is labeled in the UK as harmful to fish and aquatic life. The US review notes chronic risk to aquatic organisms has not been assessed due to lack of data.

Food residues
In the UK instances of illegal use cause concern. Although there have been no approvals for use on winter lettuce for some years, an enforcement survey(18) found three cases of illegal use in 1997-98, resulting in prosecutions. One example of illegal use was found on tomatoes in 1998, and strawberries in 1999.
    A survey in EU member states and Norway(19) reported on the most frequently occurring pesticide residues in national residue monitoring – vinclozolin was the seventh most frequently reported residue.

Conclusions
Regulators are concerned about potential adverse reproductive impacts of vinclozolin. The EU now appears satisfied but the US EPA remains committed to phasing out most uses of the chemical. The potential impacts of endocrine disruption have to be weighed, and US regulators are also concerned with additive impacts, as vinclozolin may share a common mechanism of toxicity with other fungicides, procymidone and iprodione. (PB)

References
1. R. Whitehead, The UK Pesticide Guide 2000, British Crop Protection Council and CABI Publishing, 2000, pp 555-6.
2. C.D.S. Tomlin, Ed, The Pesticide Manual (11 Edn), BCPC, 1997, pp1267-8.
3. D.G. Garthwaite & M.R. Thomas, Arable Farm Crops in Great Britain 1998, Pesticide Usage Survey Report 159, Pesticide Usage Survey Group, York, 1999.
4. Overview of the Vinclozolin Risk Assessment, US Environment Protection Agency, Office of Pesticide Programs Reregistration document, 26 July 2000. 
5. World Health Organisation Recommended Classification of Pesticides by Hazard 1998-99 WHO/PCS/98.2), WHO, Geneva 1999.
6. Op. cit. 1.
7. Op. cit. 4.
8. Vinclozolin, Extoxnet Pesticide Information Project, Cornell University, US, June 1996.
9. Vinclozolin, Evaluation Document 34, Ministry 
of Agriculture, Fisheries and Food, London, 1991.
10. Vinclozolin. Evaluation Document 113, MAFF, York, November 1994.
11. Opinion regarding the reproductive effects of vinclozolin, European Commission DG XXIV (Document reference SCP/VINCLO/019-Final), 
28 October 1999.
12. Op. cit. 4.
13. Commission moots priority list of endocrine chemicals, ENDS Report 306, July 2000.
14. Hormone Disrupting Substances in the Environment, DETR, http://www.environment.detr. gov.uk/hormone/index.htm 
15. Op. cit. 8.
16. Opinion regarding the evaluation of vinclozolin, European Commission (DG XXIV/B/B2) Document reference SCP/VINCLO/021-Final, 31 March 2000.
17. Op. cit 1.
18. Annual Report of the Working Party on Pesticide Residues 1997, MAFF Publications, London 1998.
19. Monitoring for pesticide residues in the EU 
and Norway – Report 1997, European Commission.

[This article first appeared in Pesticides News No.50, December 2000, p21]