Table 6. Technical products not included in the WHO Classification and believed to be obsolete or discontinued for use as pesticides

Source: WHO 1996.

Table 7. List of gaseous or volatile fumigants not classified under the WHO Recommended Classification of Pesticides by Hazard

Note: The WHO Classification does not set out any criteria for air concentrations on which classification could be based. Most of these compounds are of high hazard and recommended exposure limits for occupational exposure have been adopted by national authorities in many countries.

Source: WHO 1996.

The entries and abbrevations used in the tables’ various columns are explained here under the corresponding heading.

Name

The first column in the tables list the approved name of active ingredients. Trade names are not listed since there are many of these.

Status

The following abbreviations are used:

• ISO: Indicates the common name approved by the International Organization for Standardization (ISO). Such names are, when available, preferred by the WHO to all other common names. However, some of these names may not be acceptable for national use in some countries. If the letters ISO appear within parentheses (e.g., with fentin acetate), this indicates that ISO has standardized (or is in the process of standardizing) the name of the base, but not the name of the derivative listed in the “Name” column. (Fentin is an ISO name, but fentin acetate is not.)
• N( ): Indicates approval by a national ministry or other body, which is shown in parentheses as follows: A: United States Environmental Protection Agency (EPA), American National Standards Institute (ANSI), the Weed Science Society of America or the Entomological Society of America; B: British Standards Institution or the British Pharmacopoeia Commission; F: Association française de normalisation; J: Japanese Ministry of Agriculture and Forestry; U: Gosudarstvennyi Komitet Standartov, former USSR.
• C: Chemical, trivial or other common name.

Main use

In most cases only a single use is given. This is only for identification purposes and does not exclude other uses. The following abbreviations are used:

• AC: acaricide
• AP: aphicide
• B: bacteriostat (soil)
• FM: fumigant
• F: fungicide, other than for seed treatment
• FST: fungicide, for seed treatment
• H: herbicide
• I: insecticide
• IGR: insect growth regulator
• Ix: ixodicide (for tick control)
• L: larvicide
• M: molluscicide
• N: nematocide
• O: other use for plant pathogens
• PGR: plant growth regulator
• R: rodenticide
• RP( ): repellent (species)
• -S: applied to soil; not used with herbicides or PGRs
• SY: synergist.

Chemical type

A limited number of chemical types are shown in this column. Most have some significance in the sense that they may have a common antidote or may be confused in the nomenclature with other chemical types. For example, thiocarbamates are not cholinesterase inhibitors and do not have the same effects as carbamates. The following abbreviations are used:

• C: carbamate
• CNP: chloronitrophenol derivative
• OC: organochlorine compound
• OM: organomercury compound
• OP: organophosphorus compound
• OT: organotin compound
• P: pyridyl derivative
• PA: phenoxyacetic acid derivative
• PY: pyrethroid
• T: triazine derivative
• TC: thiocarbamate.

These chemical classification are included only for convenience and do not represent a recommendation on the part of the WHO as to the way in which pesticides should be classified. It should, furthermore, be understood that some pesticides may fall into more than one type.

Chemical type is not shown where it is apparent from the name.

Physical state

This refers only to the technical compound. The following are used:

• L: liquid, including solids with a melting point below 50C
• oil: oily liquid; refers to physical state only
• S: solid, includes waxes.

It may happen in a few cases that where the technical product is a solid, highly concentrated liquid formulations may need to be classified in a more hazardous class. In most cases, oils have been classified as liquids unless very viscous at ordinary temperatures.

Route

Oral route values are used unless the dermal route values place the compound in a hazardous class or the dermal values are significantly lower than the oral values, although in the same class. The following abbreviations are used:

• D: dermal
• O: oral.

LD₅₀ (mg/kg)

The LD₅₀ value is a statistical estimate of the number of mg of toxicant per kg of body weight required to kill 50% of a large population of test animals; the rat is used unless otherwise states. A single value is given: “c” preceding the value indicates that it is a value within a wider than usual range, adopted for classification purposes; “+” preceding the value indicates that the kill at the stated dose was less than 50% of the test animals.

The toxicity data for pyrethroids are highly variable according to isomer ratios, the vehicle for oral administration and the husbandry of the test animals. The variability is reflected in the prefix “c”. The single LD₅₀ value now chosen for classification purposes is based on administration in corn oil and is much lower than that in aqueous solutions. This has resulted in considerable changes in the classification of some products and also underlines the need for classification by formulation if labelling is to reflect true hazard.

The figures in this column are not median values; rather, a safety margin is incorporated by choosing the lower confidence limit in most cases. Where a sex difference occurs in LD₅₀ values, the value for the more sensitive sex is used. A number of classification adjustments have been made in respect of some pesticides and these are explained. A borderline case has been classified in the more or less hazardous class after consideration of its toxicology and use experience.

In table 5, a number of pesticides are listed as unlikely to present any acute hazard in normal use. The WHO Classification is open-ended but it is clear that there must be a point at which the acute hazard posed by the use of these compounds is so low as to be negligible provided that the necessary precautions are taken. For the purposes of this table, it has been assumed that this point is an oral LD₅₀ of 2,000 mg/kg for solids and 3,000 mg/kg for liquids. However, it should not be overlooked that in formulations of these technical products, solvents or vehicles may present a greater hazard than the actual pesticide and therefore classification of a formulation in one of the higher hazard classes may be necessary.

Biological pesticides are not included in the WHO Classification because the methods of the safety testing of live biological agents are not appropriate to classification procedures applied to chemical compounds.

Remarks

Where the classification of a technical product has been adjusted, the basis for this is indicated in this column. Major irritant properties are noted; these do not affect classification. Where the name of a technical product is cross-referenced, the referenced product will be found in the same table. Abbreviations are used to indicate that a WHO/FAO Data Sheet (DS) or an issue of International Programme on Chemical Safety (IPCS) Environmental Health Criteria (EHC) Series or Health and Safety Guide contains further information on the product; the relevant issue numbers follow the abbreviations.

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