TOXICOLOGY INVESTIGATION INTO BINKILL GARBAGE BIN FUMIGATION PRODUCT FOR WASTE AND COMMUNITY PROTECTION DIVISION PENRITH COUNCIL Parts 1 and 2 TOXICOLOGIST: CHRIS DERRY UNIVERSITY OF WESTERN SYDNEY JUNE 2010 ABSTRACT In March 2010 the University of Western Sydney was requested by Penrith City Council to carry out a toxicological assessment of the potential use by residents of Penrith Council area of a commercial pesticide product, Binkill, with potential for exposure to residents, their families and pets. The product was to be used as recommended by the manufacturer by residents as a slow release fly killer contained in a capsule to be placed by householders in bulk collection bins for green and kitchen waste, with the intention of controlling flies and their immature forms during storage, pending collection as part of a municipal composting operation. Part 1 of this toxicology report concerns a critical review of the research literature relating to dichlorvos and naphthalene as the main active ingredients. This review was not to be merely a summary of findings in relevant literature, but an evaluation of those findings with relevance to the safe use of the product in the intended household setting, with exposition of any problems which might be envisaged from a toxicological perspective. Part 2 of the report is an original health risk assessment based on the use of Binkill itself in terms of the device which is used to contain the active ingredients, labelling of the product packaging and device, risk to Penrith Council staff or public in terms of storage, handling use and disposal of the product, and potential local threats to the environment as a consequence of using the product. In this section potential hazards were identified, risks characterised and a framework established for their prioritisation. Information gathered in terms of this scientific research was required to inform Council to enable them to take proactive measures for managing risk, and to enable them to move forward with the current widely-supported recycling program, with regard to duty of care towards Penrith City residents, visitors, staff, and others. Some initial conclusions of the investigation were that dichlorvos was a good pesticide of choice for the intended application in terms of its relatively low health risk, effectiveness in killing adult flies and immature forms of the family Muscidae, ability to dissipate rapidly, and ease of availability and use. Problems with which Council should be concerned in terms of the intended, Council- sanctioned use were identified and described with recommendations for Council action. The main problems included labelling inadequacies, visible chips of pesticide material outside the capsule in the surrounding plastic wrapping, and inadequate child-proof nature of the packaging. A number of other items with acceptably low risk were identified for the information and general consideration of Council and the manufacturer. In addition to the specific safety recommendations mentioned above, suggestions for educational material for residents, and a controlled system for distribution of the product at residential level, were made. 1 TOXICOLOGY REPORT ON BINKILL GARBAGE BIN FUMIGATION PRODUCT FOR WASTE AND COMMUNITY PROTECTION PENRITH COUNCIL PART 1: TOXICOLOGY REPORT ON DICHLORVOS AND NAPHTHALENE TOXICOLOGIST: CHRIS DERRY UNIVERSITY OF WESTERN SYDNEY JUNE 2010 2 INDEX SECTION PAGE DICHLORVOS 3 Introduction 3 Status of dichlorvos in Australia 3 Background to the organophosphate (OP) pesticides 7 Toxicity of dichlorvos relative to other substances 8 Forms of dichlorvos pesticides in use 9 Why dichlorvos is regarded as safer than many other pesticides 10 Present uses in Australia 11 Application methods which may be prohibited in Australia 12 Future of pvc resin strips for small space fumigation 13 Future of dichlorvos/naphthalene blocks for small space fumigation 14 Physiological action of dichlorvos 15 Health outcomes of poisoning 16 First aid treatment 19 Environmental toxicity: animals 20 Environmental toxicity: plants 20 Environmental fate 20 Identifiers of dichlorvos 21 Properties of dichlorvos 21 Storage of dichlorvos 22 Spills and leaks 22 NAPHTHALENE 24 Sources and qualities 24 Exposure and health effects 24 Mode of action 27 Toxicodynamics/kinetics 27 First Aid 27 Ecological effects 28 Properties of naphthalene 28 REFERENCES 30 APPENDIX 1: DATA BASES REVIEWED 33 3 TABLE PAGE Table 1: Substances less toxic than dichlorvos in air 8 Table 2: Substances more toxic than dichlorvos in air 9 Table 3: Method of application, and preliminary APVMA recommendation 12 Disclaimer: The report was produced after consultation of the resources shown in Appendix 1 and includes comments by the toxicologist. The contents do not represent the official opinion of the University of Western Sydney. 4 DICHLORVOS INTRODUCTION Part 1 of this toxicology report is based on a critical review of the literature relating to dichlorvos and naphthalene as the main active ingredients in the fumigant product, Binkill. In other words, it is not merely a summary of findings in relevant literature, but an evaluation of those findings with relevance to the safe use of the product in an intended household setting, with implications. A list of resources consulted in the preparation of this report is contained in Appendix 1 of Part 1. The report is not designed as a scientific treatise on the substances and their potential health impact, but as a guide to Council offering sufficient clarity and explanation to elucidate the content and implications of use of the product, in terms of the original scientific literature. STATUS OF DICHLORVOS IN AUSTRALIA Binkill is described by the Australian Pesticides and Veterinary Medicine’s Authority (APVMA) as a home garden product, with a dichlorvos content of 80 g/kg and a naphthalene content of 800 g/kg, used in the control of flies and maggots in garbage bins. It was one of the first four products containing dichlorvos to be approved and registered for use by the APVMA and is still registered with the product code 47695. In December 1996 the APVMA announced that it would be carrying out review of seven chemicals of concern, including dichlorvos, and produced a preliminary review document for public and institutional consideration and comment in June 2008. This is still open for consultation (APVMA, 2008). This concern was apparently born of growing international concern relating to the impact of a range of pesticide products on health and the environment, and the investigation, in response, of a range of pesticide products by the American Environmental Protection Agency (EPA). In the report on preliminary findings from the APVMA (2008) a large number of practices involving application of liquid dichlorvos have been disapproved of, and advice has been given that they should be modified or discontinued. At present comments on these recommendations are being called for from the public and certain relevant scientific disciplines. It is probable that when the review is finalised legislative change may be sought to control some of these applications. Disapproval has been based more on an inability to adequately protect staff from the chemical using known approaches and available personal protective equipment (PPE), than on its extensive use in food products both for local use and for export from Australia. In this regard, over 55% of dichlorvos use in Australia is for agricultural application with up to 10 000 tonnes of grain being treated daily for export and local use. Despite the extensive use of dichlorvos in many food production and storage industries, two Australian Total Diet Surveys in 2002 and 2003 respectively, performed under the strict control of the Food Standards Australia New Zealand (FSANZ), failed to detect the pesticide in any of the food 5 items surveyed although application to most of these had occurred (APVMA, 2008). This lack of residue makes dichlorvos exceptional among directly applied pesticides. This lack of residue is partly due to dichlorvos’ volatility in comparison with the other organophosphate (OP) pesticides in common use. It has a vapour pressure of 145 mg/m3 at 20°C, with a boiling point of 140 ºC. It therefore has to be dissolved in a less volatile substance to prevent ready evaporation at room temperature, and as it is non-polar it is dissolved in other non-polar substances such as oil, long-chain alcohols, naphthalene and plastic resins, such as PVC resin. Its properties of volatility and non-polar solubility give it advantages and disadvantages. Because it vaporises easily it can be used as a fumigant whereas other OP pesticides cannot. This gives it the useful property of penetrating stored grain and other material to reach insects which it also penetrates by dissolving in their fatty structures and reaching target sites in the arthropod nervous system. As a result it does not have to be sprayed onto surfaces like other OP pesticides, where a residue can remain to be potentially picked up by the hands of staff or to be ingested by the consumer. A disadvantage is that it can enter the human body by all three main exposure routes, inhalation, ingestion and contact, easily passing the cellular phospholipid barrier as a non-polar substance. It is also very penetrative, going into cracks and crevices and even dissolving in plastic material and structures from which it is then slowly released. After fumigation using dichlorvos dissolved in a slow-release liquid it can remain in air pockets between structures and substances or is slowly released from non-polar substances in which the oil or alcohol base has dissolved. This presents a post-fumigation hazard and the APVMA advises a four-day vacancy with airing prior to occupation when dichlorvos liquid in solvent base has been used to fumigate indoor habitable spaces. Once inside the human body its action presents a physiological paradox. It is extremely rapidly metabolised (broken down) its half life being an incredible 8 to 20 minutes (Leikin & Paloucek, 2008) so that repeated exposures do not present the same accumulation hazard noted with many other pesticides.