General list of impurities and classes of impurities of toxicological concern for agricultural active constituents

The APVMA has overall responsibility for the regulation of active constituents used in agricultural and veterinary chemical products. In particular, the APVMA is required to serperately approve active constituents, and with limited exceeptions, each source (manufacturing site) of an active constituent must be approved. Section 14 (1)(b) of the Agricultural and Veterinary Chemicals Code (Agvet Code) requires that, before granting an application for the approval of an active constituen, the APVMA must be satisfied that the active constituent meets the safety criteria. The safety criteria and the matters to which the APVMA must have regard in determining whether an active constituent satisfies the safety criteria are in turn defined in section 5A of the Agvet Code. Relevant matters for the purpose of discussion of the safety criteria in relation to impurities in active constituents are given section 5A(2)(a)(i)-(iv):

For the purposes of being satisfied as to whether an active constituent meets the safety criteria, the APVMA:

(a)  must have regard to the following:

(i)  the toxicity of the constituent and its residues, including metabolites and degradation products, in relation to relevant organisms and ecosystems, including human beings;

(ii)  the method by which the constituent is, or is proposed to be, manufactured;

(iii)  the extent to which the constituent will contain impurities;

(iv)  whether an analysis of the chemical composition of the constituent has been carried out and, if so, the results of the analysis;

An integral part of the evaluation process for an active constituent is the assessment of its chemical composition.

To a large degree, the safety, efficacy and environmental impact of agricultural and veterinary chemical products are dependent on the composition of the active constituents. When each new agricultural active constituent completes the approval process, the APVMA establishes a standard for it. The standard typically specifies the minimum purity of the active constituent, the ratio of isomers to diastereoisomers where relevant, and the maximum level of any impurities of toxicological significance. The toxicological profile of the active constituent is directly linked to its purity and the associated impurities.

In addition to the instances where maximum limits for toxicologically significant iimpurities are listed in the standard for a specific active constituent, the APVMA maintains a general list of impurities and classes of impurities of toxicological concern. These impurities can have an adverse impact on human health, the environment or both.

In any application for approval of a new active constituent, or a new source of an existing active constituent, where there is a potential for the presence in the technical active of one or more of the impurities listed below (either as an impurity in a starting material, or as a byproduct of the manufacturing process), the APVMA requires that registrants provide information on their identities and concentration in the active constituent.

The list follows.

  • Anilines and substituted anilines
  • Dimethyl sulphate
  • Dichlorodiphenyltrichloroethane (DDT) and DDT-related impurities
  • 2,3-diaminophenazine (DAP) and 2-amino-3-hydroxyphenazine (AHP)
  • Ethylene thiourea (ETU) and propylene thiourea
  • Halogenated dibenzodioxins and halogenated dibenzofurans
  • Hexachlorobenzene (HCB)
  • Hydrazines and substituted hydrazines
  • Methyl isocyanate
  • Nitrosamines
  • Oxygen analogues of organophosphates
  • Polychlorinated biphenyls (PCBs)
  • O,O,O’,O’-tetraethyl dithiopyrophosphate (S,S-TEPP or Sulfotep) and O,O,O’,O’-tetraethyl monothiopyrophosphate (O,S-TEPP)
  • Sulfoxides and sulfones of organophosphates and carbamates
  • 3,3’,4,4’-tetrachloroazobenzene (TCAB) and 3,3’,4,4’-tetrachloroazoxybenzene (TCAOB)

If you have any queries concerning the standards for active constituents, please contact:

Chemistry and Manufacture
Phone: +61 2 6210 4823
Email: chemistry@apvma.gov.au

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