|Approaches for better information and monitoring of POPs in articles|
|Monitoring of POPs in articles and products|
|Alternative assessment approaches for chemical alternatives|
|Screening of potential POPs in chemical databases|
|Tools for the assessment of POPs properties of chemicals|
|Toxicity assessment of alternatives|
|Case study: Scientific assessment of a PFOS alternatives in chromium plating|
US EPA PBT Profiler
The PBT Profiler (http://www.pbtprofiler.net/) was designed to be an easy to use, widely available, no-cost tool to screen chemicals lacking experimental data in order to help identify pollution prevention (P2) opportunities. It is a continuation of the Office of Chemical Safety and Pollution Prevention (OCSPP, U.S. Environmental Protection Agency) Pollution Prevention (P2) Assessment Framework - a collection of screening models and methods to help promote the design, development, and application of safer chemicals and processes. The methodology the PBT Profiler uses has been developed by government, academic, and private-sector researchers over the past 20 years and represents some of the best techniques currently available. The P2 Framework uses computerized methods, such as structure/activity relationships (SARs) and standard scenarios, to predict risk related data (physical/chemical properties, bioconcentration, environmental fate, carcinogenicity, toxicity to aquatic organisms, worker and general population exposure, and other information) on chemicals lacking experimental data.
Purpose. The PBT Profiler uses a subset of P2 Assessment Framework computer-based tools to help identify chemicals that potentially may persist, bioaccumulate, and be toxic to aquatic life, i.e., PBT chemicals. The release of even small amounts of persistent, bioaccumulative, and toxic chemicals to the environment is of concern because they can accumulate over time to higher concentrations and, therefore, have a higher potential to adversely impact human health and the environment. The overwhelming majority of known chemical substances do not have experimental persistence, bioaccumulation, and toxicity data available. Only a small fraction of chemicals currently in commerce, including the 2,000 new chemicals introduced each year, have sufficient data available to perform a thorough evaluation of potential risks. The PBT Profiler was designed to help interested parties voluntarily screen chemicals for persistence, bioaccumulation, and aquatic toxicity characteristics when no experimental data are available.
Limitations. It is important to stress that the PBT Profiler is a screening level predictive tool and cannot be used for all chemical substances. Nevertheless, the PBT Profiler is a tool that, like all tools, has strengths, weaknesses, and limitations. These limitations should be considered before using this model. For example, predicted data should never be used in place of experimental data. Additional model limitations are described on this web site. When properly applied, the PBT Profiler can provide a straight-forward estimate of persistence, bioaccumulation, and aquatic toxicity based on widely accepted criteria. This information can help interested parties to identify pollution prevention initiatives and aid in their chemical selection processes.
Advantages. Many chemicals can be profiled in one on-line session. The PBT Profiler provides three integrated levels of output for each chemical including (1) easy to read color-coded comparisons of predicted values to PBT criteria; (2) predicted values for P, B, and T; and (3) narrative descriptions of pollution prevention considerations for each chemical. For rapid recognition of the estimated results, the "P", "B", and "T" designators (corresponding to persistence, bioaccumulation, and toxicity, respectively) are shaded orange or red if a chemical exceeds the defined thresholds for each criteria; if the thresholds are not exceeded, the designators are shaded green. Numeric estimates in a tabular format are also provided for persistence (in air, water, soil, and sediment), bioaccumulation, and toxicity. To put these results in perspective, pollution prevention considerations for each chemical profiled are also provided in narrative available by clicking on the “P2 Considerations” link on the Results page. More information on interpreting the PBT Profiler estimates is available on the PBT web site.
A case study on the assessment of alternatives to a POP (PFOS related substance as pesticide) using the PBT profiler can be found in "Case study: Use of PBT Profiler for assessing sulfluramide alternative pesticides".
The Stockholm Convention Regional Centre for Capacity-building and the Transfer of Technology in Asia and the Pacific at Tsinghua University (Beijing/China) has assessed alternative pesticides to sulfluramide using the PBT profiler.
Sulfluramid (N-ethyl perfluorooctane sulphonamide, CAS No.: 4151-50-2) is a perfluorinated active ingredient (AI) in insecticides commonly used to control the insects with highly social behaviour patterns, such as termite, red fire ant, and cockroach. These insecticides use sulfluramid at a certain concentration (e.g. 3 g/kg), mixed with citric fruit pulps and soybean oil. The mixture of these materials is extruded to form pellets of the insecticide, which are usually called baits. Since 1990s, sulfluramid has been adopted as AI in some commercial bait products, e.g. FirstLine® termite defense system from FMC Corporation, Mirex-S bait from Aracruz Celulose S.A. Company, Brazil.
China is still producing and using sulfluramid now, about 4-8 t/y of PFOSF was used to formulate in sulfluramid manufacture according to the survey in 2008. Currently there are five sulfluramid containing pesticide products from two producers legally registered in China. These products are mainly for the control of termite and cockroach. Among them, Yekang bait for cockroach control has been successfully recommended by the organization committee of both Beijing 2008 Olympic Games and Shanghai Expo2010 China, with the annual sale of about 5 million USD. On August 30, 2013, China’s Standing Committee of the National Congress ratified the amendments to Annexes A, B and C to the Stockholm Convention to list nine new persistent organic pollutants, including perfluorooctane sulfonic acid, its salts and perfluorooctane sulfonyl fluoride. Chinese Government submitted the ratification to the Depositary of the Stockholm Convention on December 26, 2013, and the amendments entered into force for China from March 26, 2014. A 12-ministry joint announcement was issued on March 25, 2014. There are 7 acceptable purposes and 6 specific exemptions out of Annex B for PFOS that have been verified and registered at the Secretariat of the Stockholm Convention by the Chinese Government. However the pest control using sulfluramid has not been registered. Therefore as a Party to the Convention, China has to find cost-effective and environmentally sound alternatives to replace the sulfluramid as soon as possible.
Alternatives on the Chinese market
There are many competitive insecticide products on the Chinese market; however their environment related properties have not been reviewed comprehensively. Therefore in a research study conducted at the Stockholm and Basel Convention Coordination Center at Tsinghua University (Beijing/China), the sulfluramid substitutes contained in registered bait products available in Chinese market were reviewed. A preliminary assessment on their PBT (i.e. persistence, bioaccumulation and toxicity) profiles was conducted using a screening-level tool (PBT profiler) developed by the Environmental Health Analysis Center under contract to the Office of Chemical Safety and Pollution Prevention, U.S. Environmental Protection Agency. Also the WHO recommended classification of pesticides by hazard was used for comparison.
Review of existing sulfluramid substitutes
According to China’s Regulation on Pesticide Administration (RPA), all pesticide products should be registered before their production and sale in the Chinese market. There’s an official database of registered pesticide products in China, which is maintained by the Institute for Control of Agrichemicals at the Ministry of Agriculture (ICAMA). This database can be accessed via internet (http://www.chinapesticide.gov.cn/, in Chinese). Defining the search keywords as “bait” for “formulation”, “termite” and “cockroach” for “target pest species”, all records of registered bait products for termite and cockroach control can be obtained.
According to the database search results, there are 3 bait products for termite control using 2 AIs other than sulfluramid registered in China; also there are 133 bait products for cockroach control using 20 AIs other than sulfluramid registered in China (including 1 inorganic chemical, 16 organic chemicals, 3 biogenic substances).
Assessment of persistence, bioaccumulation and toxicity of the alternatives
The assessment of persistence, bioaccumulation and toxicity was conducted using the PBT Profiler (http://www.pbtprofiler.net/, Version 2.000, last updated September 4, 2012) developed by U.S. EPA, which is a screening-level tool that provides estimates of the persistence, bioaccumulation, and chronic fish toxicity potential of chemical compounds. The PBT Profiler employs methodologies that calculate or otherwise estimate PBT characteristics based on an analysis of chemical structure. According to EPA, PBT estimations rendered by the PBT Profiler are not sufficient for definitive PBT determinations. The PBT Profiler is rather a research, not regulatory, tool to identify chemicals that may need further evaluation for potential Persistence, Bioaccumulation and Toxicity characteristics (http://www.pbtprofiler.net/notice.asp).
Considering the principle of the PBT profiler, inorganic AI (boric acid) and biogenic AIs (i.e. emamectin benzoate, metarhizium anisopliae, periplaneta fuliginosa desovirus (PfDNV)) were excluded in the assessment. The results for the other 16 AIs obtained from PBT profiler are summarized in table 23.
Both persistence and toxicity of all AIs are labeled as either Orange or Red, which mean moderate or high concern (for toxicity) and persistent or very persistent (for persistence). However, most AIs are of low overall PBT concern since they belong to the category of “not bioaccumulative” (Green) (table 23). Only three organofluorine AIs (i.e. flufiprole, hexaflumuron and chlorfluazuron) are classified into the category of “considered bioaccumulative” (Orange) (table 23). Therefore the PBT profiles of these three AIs are very similar with that of sulfluramid, as they have the same colors: red for persistence and toxicity and orange for bioaccumulation. Therefore according to the PBT profiler it is necessary to further investigate the safety of these AIs.
Table 23. Classification and criteria used by PBT Profiler and the WHO hazard classification
* Note: II = Moderately hazardous; III = slightly hazardous; U = Unlikely to present acute hazard in normal use; NA = Not available
Further discussion about the hazard of pesticide AIs in us
According to the WHO recommended classification of pesticides by hazard (WHO 2010), most of the alternative AIs are classified as “II” (i.e. moderately hazardous), as shown in the table above. As the exception, three AIs are of “U” (i.e. unlikely to present acute hazard in normal use), including chlorfluazuron, hexaflumuron and tetramethrin; also chlorbenzuron is classified as “III” (i.e. slightly hazardous). Compared with sulfluramid which is also classified as “II”, the existing AIs seem to be at the same level or lower level in terms of hazard.
One AI (flufiprole) is labelled as “NA” (Table 23) since this AI is China-specific and rarely used in other countries and therefore not covered by the WHO guideline. Flufiprole was developed by Dalian Raiser Pesticides Co., Ltd in 2002 (Patent No. PCT/CN03/00343) is a new fipronil derivative. The 0.2% flufiprole-based bait product for cockroach control obtained its full registration in 2013 (Certificate No.: WP20130225), which was labelled as “slightly toxic”. It has been well accepted due to its low toxicity to fish, shrimp and crabs. The acute toxicity of technical material of flufiprole for male/female rat is as below: LD50>=4640 mg/kg (oral), LD50>=2150 mg/kg (dermal).
In the present study, the existing baits for termite and cockroach in Chinese market were reviewed by searching the official Chinese database of registered pesticides. Twenty AIs have been identified in totally 136 registered bait products, among which 16 chemogenic organic AIs were further assessed for their persistence, bioaccumulation and toxicity using the U.S.EPA’s online software - PBT profiler. Also the WHO recommended classification of pesticides by hazard was used for comparison.
Combining the PBT profiles and classification by hazard, the existing AIs seem to be better in terms of environmentally soundness. The results from this preliminary assessment confirmed that none of sulfluramid AIs adopted by currently registered bait products for termite and cockroach belong to the POPs group. However, that it is necessity to further evaluation the PBT quality of the used organofluorine. Overall the applicability of the U.S. EPA PBT profiler as a useful screening tool has been illustrated.
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OECD provides the so called “OECD POV and LRTP Screening Tool” whose purpose is to estimate overall environmental persistence (POV) and long-range transport potential (LRTP) of organic chemicals at a screening level, and to provide context for making comparative assessments of environmental hazard properties of different chemicals. The Tool requires estimated degradation half-lives in soil, water and air, and partition coefficients between air and water and between octanol and water as chemical specific input parameters. From these inputs The Tool calculates metrics of POV and LRTP from a multimedia chemical fate model, and provides a graphical presentation of the results.
The tool is accompanied by a description manual, which includes 3 sections. Section 1 is an introduction to ‘The Tool’ software, instructions for performing different types of calculations and for customizing the presentation of results. Section 2 provides guidance for interpreting results from ‘The Tool’, including definitions of the POV and LRTP metrics. Section 3 presents a brief history of ‘The Tool’ that describes its development and relationship to other multimedia chemical fate models.