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Pesticide information box

© RPB
v. 4/5/2010

Mammalian Toxicity Classification

i. The World Health Organisation (WHO) provides an internationally recognised system for classifying the hazard of pesticides. They are grouped in terms of their median lethal dose (LD50 to rats: mg/kg body weight) from Class I (most toxic) to Unclassified (unlikely to cause harm with normal use) with each class bounded by a 10-fold range of dose. The WHO system recognises a 4-fold reduced hazard with solid formulations, in comparison with liquids. The classification was further developed by the US Environmental Protection Agency (EPA) which also recognises inhalation, eye and skin sensitisation effects. These classifications should be based on formulations (where such information is available).

Class

Solids

Liquids

Oral

dermal

oral

dermal

Ia

Extremely Hazardous

5

10

20

40

Ib

Highly Hazardous

6-50

11-100

21-200

41-400

II

Moderately Hazardous

51-500

101-1000

201-2000

401-4000

III

Slightly Hazardous

> 501

≥1001

> 2001

> 4001

(U)

Unlikely to present acute hazard in normal use

> 2000

-

> 3000

-

 

Certain pressure groups, including the Global IPM Facility (supported by FAO and other organisations working with Farmer Field Schools) have suggested that Class I and II products should be withdrawn from general use, since smallholder farmers are unlikely use appropriate personal protective equipment (PPE). With the development of a substantial number of new molecules since the 1980s there are now only a very few cases where class I pesticides can be justified at all, let alone for smallholder agricultural problems.

However, complications could occur if all class II products were to be withdrawn immediately. The problem here is especially with insecticides, where there is often a need for resistance management strategies involving alternations in the use of compounds of different MoA groups. Bateman (Outlooks on Pest Management 2005, 16[2]: p. 96) argued that, just as class I compounds are subdivided by WHO, it might be useful to divide class II into "IIa" and "IIb": where "IIb" formulations conform to class III dermal and inhalation toxicity for the a.i. (these being the greatest risk in normal pesticide use). This subdivision has no formal status, and was suggested in order to facilitate a phased restriction / withdrawal of the more hazardous compounds, before safer products became identified and available.


ii. The US Environmental Protection Agency system

Class

All formulations: LD50 (mg/kg)

Inhalation: LC50 (mg/l)

Eye effects

Skin effects

oral

dermal

I

50

200

2

Corrosive, corneal opacity not reversible within 7 days

Corrosive

II

51-500

201-2000

0.2 – 2

Corneal opacity not reversible within 7 days, irritation persisting for 7 days

Severe irritation at 72 hours

III

501-5000

 2001- 20,000

2 –20

No corneal opacity, irritation reversible within 7 days

Moderate irritation at 72 hours

IV

> 5000

> 20,000

> 20

No irritation

Mild or slight irritation at 72 hours

iii. The European Union

EU risk symbols and phrases can be found on: http://europa.eu/scadplus/leg/en/lvb/l21273.htm

These phrases have also been adopted by the International Labour Organisation on:
http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/risknote/index.htm

In 1992, the European Commission started a Community-wide review process for all active ingredients used in plant protection products within the European Union. In order to maximise "transparency on the decision making procedure", information given on their web-site: http://ec.europa.eu/food/plant/protection/evaluation/index_en.htm. "In a review process based on scientific assessments, each applicant [has] had to prove that a substance could be used safely regarding human health, the environment, ecotoxicology and residues in the food chain. This programme will be completed by 2008. From the end of 2003, the new European Food Safety Authority deals with risk assessment issues and the European Commission retains the risk management decision. The standards of this assessment and the policy of their use are constantly improved in a number of expert groups and documented in guidance documents." At the time of writing this remains a dynamic process, so readers are urged to refer to the original Europa site for authoritative information.

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