Review of Parathion - Decision Document

February 2000
NRA Review Series 00.2
Decision Document

The NRA Concludes the Review of Parathion (Parathion-ethyl) Review Background

Parathion (Parathion-ethyl) is an organophosphorus insecticide used in Australia for the control of sucking and chewing insects in the production of pome and stone fruit, vegetables, citrus, vines and lucerne.

In 1996 the NRA placed parathion under reconsideration in the first cycle of chemicals reviewed under the NRA's Existing Chemical Review Program (ECRP).  The reconsideration included a review of all aspects of the approval of the active constituent parathion, registrations of all products containing parathion, and the labels of all such products.

The reconsideration of parathion was undertaken primarily because of concerns about its high mammalian toxicity, occupational exposure concerns and potential for adverse environmental impacts.

The following product registrations and associated label approvals, as well as the listed active constituent approval, were included in the review:

Product	Registrant
Tebing Parathion Insecticide (33070)	Tebing Pty Ltd.
Farmoz Parathion E Insecticide (45585)	Farmoz Pty Ltd.
Novafos E Insecticide (48589)	Cheminova Australia Pty. Ltd.
Active Constituent	Approval Holder
Parathion-ethyl (44225)	Cheminova Australia Pty. Ltd.

Summary of Key Findings

The key findings of the review are summarised below:

Toxicology and Public Health

Assessment of available toxicological data revealed that parathion is extensively absorbed, metabolised and excreted by mammals. Long term exposure to a low concentration of parathion in the diet was without serious consequences in animal studies, although high concentrations caused symptoms consistent with the classical clinical signs associated with organophosphate poisoning. The occurrence and severity of these clinical signs were directly related to the amount of exposure.

Neither short-term nor long-term exposure to parathion appears to lead to delayed neuropathy in humans. Parathion does not interact with genetic material, and long-term cancer studies in animals provided no evidence that parathion would be associated with cancer in humans. Similarly, parathion exposure had no adverse effects on reproduction or development of the foetus in experimental animals.

Thus, the main concern arising from the toxicology review was the potential of parathion for cholinesterase inhibition. The cholinesterase inhibition endpoint was used to set public health standards.

In Australia, parathion is not registered for use in or around the home or garden. Therefore, the most likely route of exposure to parathion for the public is via residues in food arising from agricultural use. The Australian Market Basket Survey estimates the daily intake of a range of pesticides based on average food consumption. According to the 1996 survey, the highest average daily intake of parathion at a conservative 95^th percentile energy intake level in the groups studied was in girls aged 12, and was estimated at 0.0194 mg/kg/d while the lowest exposure was seen in boys aged 12 , with an intake of 0.0011 mg/kg/d. These are well below the Acceptable Daily Intake (ADI) of 1 mg/kg/d.

Occupational Health and Safety

The occupational health and safety assessment was conducted using measured worker exposure studies, published literature and predictive exposure modelling to estimate the risk to workers currently using parathion. The OHS assessment found that the margins of exposure (MOE) estimated from currently available information are inadequate for most categories of worker involved in routine uses of parathion.

Based on the information currently available, the health risk to workers during routine ground spraying (airblast, electrostatic and boom spraying) of parathion products in all crops using current mixing/loading methods and full protective equipment was unacceptable. According to the OHS assessment report, the health risk to workers with aerial application in pastures and lucerne using current practices, was also unacceptable. Increased worker controls and training were proposed for continued use of parathion, pending submission and assessment of worker exposure data.

Environmental Impact

The main concerns arising from the environmental assessment was that parathion is hazardous to bees and sensitive freshwater macrocrustacea. Application practices that can result in direct overspray or spray drift have a potential for significantly impacting on bees, and by implication other native terrestrial insects, as well as sensitive aquatic fauna, and therefore need to be addressed.

The environmental assessment focused on the use of parathion in orchards, where the hazard to aquatic organisms appeared to be acceptable at application rates of equal or less than 375 g a.i./ha. However, the hazard remained high at application rates exceeding 500 g a.i./ha, even after 24 hours. The environmental assessment concluded that restrictions regarding the rate and frequency of use and the inclusion of appropriate environmental warnings, would be required for continued registration of parathion.

While the current use pattern in orchards would not be expected to cause direct overspray, aerial application could. Reports of bee deaths were seen as a clear indication that unacceptable spray drift can occur during aerial application. Although similar environmental concerns were also raised in relation to aerial spraying of the related chemical parathion-methyl, the aquatic toxicity of parathion was found to be greater by comparison. Accordingly, the environmental assessment proposed that the current ban on aerial application of parathion in Tasmania be extended to mainland Australia.

Residue Limits

The assessment of residues was based primarily on overseas data. However, the available data were regarded as sufficient to set a series of temporary MRLs, subject to a requirement that Australian confirmatory trial data be produced for assessment.

Review Decisions and Data Requirements from Reveiw

The NRA prepared and released a draft report for public comment on its review findings of parathion in September 1998. The NRA's review of parathion highlighted several deficiencies and concerns which relate primarily to gaps in the environmental and occupational exposure databases. It also outlined the commitments required to fill data gaps and implement risk-mitigating measures.

The report and the accompanying media announcements emphasised that the future use of parathion was dependent on the generation of data to address occupational exposure and environmental concerns identified during the assessment of data.

In May 1999, a further round of targeted consultation was conducted to notify key stakeholders (producer and user industry groups, chemical registrants and States) of the data required on parathion and reiterate the regulatory consequences of not providing the same.

The data required for the NRA to be satisfied that the continued use of parathion would not pose undue hazard to workers, the environment or trade, were as follows. This data were to be submitted by 30 June 2000.

• measured worker exposure data for mixers/loaders and applicators of parathion;measured worker re-entry data for both thion and oxon residues;where low volume (LV) application equipment is in use, information on the actual application rate, dilutions needed for each crop, droplet size and potential spray drift characteristics from this equipment;environmental toxicity data for aquatic invertebrate species relevant to Australia;confirmatory residue trial data on all uses remaining on labels;
• data to allow assessment of tank mixing parathion with other anti-cholinesterase products as it relates to occupational exposure.

Although all submissions received were considered by the NRA in its final review decision, no public or other stakeholder commitment to provide data has been forthcoming and, in effect, data that is crucial to addressing the concerns raised by the review of parathion remain unavailable to the NRA.

Therefore given the absence of essential environmental,  occupational exposure and residue data, the NRA has:

1. Determined that under s.34(1) of the Agricultural and Veterinary Chemicals Code Act 1994 (Agvet Code), the NRA is not satisfied that the continued use of parathion products in accordance with the recommendations for its use as approved by the NRA:
   1. would not be an undue hazard to the safety of people exposed to it during its handling;

   2. would not be likely to have an unintended effect that is harmful to the environment; and
   3. would not unduly prejudice trade or commerce between Australia and places outside Australia.

2. Determined that under s.34(5) of the Agvet Code, the NRA is not satisfied that the conditions to which registrations and approvals for parathion can be varied in such a way that the requirements for continued registration and approval will be complied with.

3. Under s.40 of the Agvet Code, cancelled the registrations and all relevant approvals (including the active constituent approval) for parathion.

4. For the purposes of s.45(3)(b) of the Agvet Code, the following instructions were approved in respect of parathion products:
   1. that MRLs are to be cancelled as of 30 June 2001.

   2. the active constituent approval and its importation was cancelled on 11 June 1999.

5. Instructions under s.55 of the Agvet Code allows:
   1. supply of parathion by wholesale until 31 December 1999;

   2. sale of parathion by retail until 30 June 2000.

Offences

The NRA Gazette notice of 7 July 1999 stated that it will be an offence to supply by wholesale, or to have possession or custody for the purpose of such wholesale supply, parathion or products containing parathion after 31 December 1999. It will also be an offence to supply by retail, or to have possession or custody for the purpose of such retail supply, parathion or products containing parathion after 30 June 2000.

The above-mentioned Gazette notice further stated that the cancellation of registrations and approvals under the Agvet Code has the effect that it is an offence to import parathion or products containing parathion in to Australia after 11 June 1999.  In this regard, section 69B of the Agricultural and Veterinary Chemicals (Administration) Act 1992 provides that a person must not, without reasonable excuse, import into Australia an unapproved active or an unregistered chemical product unless the NRA has consented in writing to the importation, or the NRA has exempted the active or product from the operation of the section.

Future Registrations and Approvals

The NRA may consider new applications for parathion where they meet the requirements for registration/approval of agricultural chemicals in force at the time of submission. It is expected that the supporting data for such applications include the occupational exposure, environmental and residue trial data noted above. Prospective applicants should contact the NRA (see Further Information below).

Status of Review and Protected Data

The ECRP review of parathion was concluded with the NRA Board decision to cancel registrations and active constituent approvals for parathion in June 1999. The publication of this document on the NRA Internet Website is intended to provide information for the benefit of persons interested in the ECRP review or possible future registrations of parathion.

A significant package of data was evaluated as part of the ECRP review of parathion. Consistent with Part 3 of the AgVet Code, where these data meet the applicable criteria for protection they are eligible for protected information status. As there have been no on-going registrations for parathion beyond June 1999, data compensation issues have not arisen at this stage. However, prospective applicants should be aware that any future registrations or approvals for parathion may require data compensation.

Further Information

Reports of the NRA assessment of agricultural aspects, toxicology, occupational exposure and environmental impacts have remained unchanged from the ones posted on the NRA Website in September 1998. For specific NRA Board decisions and instructions for using parathion or products containing parathion during the phase out period (1999 - 2001), please refer to the notice entitled "Outcomes of the Review of Parathion" in the NRA Gazette dated 6 July 1999, pp 30-32. A Media Release dated 9 July 1999 is also available for parathion.

Chemical Review Section
21^st February 2000