DETERMINATION ON WHETHER A SUBSTANCE IS A HAZARDOUS SUBSTANCE PURSUANT TO SECTION 26 OF THE HSNO ACT Application Code HAZ03001 Application Type Section 26 – determine whether a substance is hazardous under the HSNO Act. Applicant Plastics New Zealand (Inc) Date Application Received 2 April 2003 To be considered by The Hazardous Substances Standing Committee of the Authority. Purpose of the Application To determine whether or not certain fluoropolymers are hazardous Noel McCardle Applications Advisor (Operations Group) Scientific Advisor (Science & Analysis Group) Tania van Maanen Introduction Fluoropolymers are a class of polymers analogous to polyolefins in which some or all of the hydrogen atoms have been replaced by fluorine (and possibly other halides). Fluoropolymers (the most well-known of which is poly(tetrafluoroethylene) [PTFE] or Teflon®), are extremely inert with excellent thermal and chemical resistance and exceptional anti-frictional qualities. These properties are exploited in applications such as non-stick cookware, ball bearings, piping, gaskets, containers that need to be chemically resistant, and human organ prostheses. No polymer manufacture is currently undertaken in New Zealand. Plastics are imported into the country in the form of granules from which a range of products are manufactured. Manufactured articles are exempt from the HSNO approval process but polymer granules fall within the HSNO definition of a substance and as such, a HSNO approval is required if any of the HSNO hazardous property thresholds are exceeded. Substance Definition For the purposes of this section 26 determination, fluoropolymers are defined as a class of polymers analogous to polyolefins in which some or all of the hydrogen atoms have been replaced by fluorine (and possibly other halides). Further, the definition is limited to those fluoropolymers (not containing additives) with a number average molecular weight greater than 10 000 amu and with residual monomer, catalyst and solvent impurities present at levels less than 0.1%. In addition, polymers that are cationic (or potentially cationic) or those that are water absorbing, are specifically excluded from this definition. ERMA New Zealand section 26 determination HAZ03001 Page 1 of 19 Examples of fluoropolymers are listed in the application form HS7, provided as Appendix 1 to this document. Hazardous Property Assessment An assessment of fluoropolymers against the HSNO thresholds was provided in the application form (attached as Appendix 1 to this document). It is noted that often limited or no information was available on these types of substances for a number of endpoints, especially data on fluoropolymers as a group. Where information was available on specific fluoropolymers, this has been provided. However, it is recognised that this s26 determination is limited to fluoropolymers of very high molecular weight (i.e. greater than10 000 amu) and as discussed in the application form, such substances are not likely to be bioavailable and therefore highly unlikely to adversely affect either human health or the environment. A summary of the hazardous property assessment is provided below. Class / Sub-class Detail Threshold Class 1 – Explosiveness Fluoropolymers are not considered explosive. They do not meet the HSNO criteria for an explosive substance and are not listed in the UN Recommendations on the Transport of Dangerous Goods. Not triggered Class 2,3,4 – Flammability Fluoropolymers are not considered flammable. They do not meet the HSNO criteria for a flammable substance and are not listed in the UN Recommendations on the Transport of Dangerous Goods. Not triggered Sub-class 5.1 – Oxidisers Fluoropolymers do not meet the HSNO definition/criteria for an oxidising substance. Not triggered Subclass 5.2 – Organic peroxides Fluoropolymers do not meet the HSNO definition/criteria for an organic peroxide. Not triggered Sub-class 6.1 – Acute toxicity Fluoropolymers are not considered to be acutely toxic as defined by the HSNO criteria. Rats fed PTFE at a level of 12500 mg/kg showed no toxic effects. The oral LD50 of the terpolymer (vinylidene fluoride-haxafluoropropylene-tetrafluorethylene) was greater than 40000 mg/kg. Rats fed the vinylidene fluoride-haxafluoropropylene copolymer at 12500 mg/kg showed no clinical or nutritional signs of toxicity. Not triggered ERMA New Zealand section 26 determination HAZ03001 Page 2 of 19 Class / Sub-class Detail Sub-class 6.3 – Skin irritancy Fluoropolymers are not considered to be skin irritants Not triggered as defined by the HSNO criteria. Skin irritation tests with PTFE did not produce skin irritation. Polyvinyl fluoride tested negative for skin irritation. Skin irritation tests on the terpolymer (vinylidene fluoridehaxafluoropropylene-tetrafluorethylene) and the copolymer vinylidene fluoride-haxafluoropropylene produced only mild and transient responses, insufficient to trigger HSNO thresholds. Sub-class 6.4 – Eye irritancy Fluoropolymers are not considered to be eye irritants as defined by the HSNO criteria. Eye irritation tests on the terpolymer (vinylidene fluoridehaxafluoropropylene-tetrafluorethylene) and the copolymer vinylidene fluoride-haxafluoropropylene produced only mild and transient responses, insufficient to trigger HSNO thresholds. Not triggered Sub-class 6.5A – Respiratory sensitisation No information was located to indicate that fluoropolymers would be respiratory sensitisers as defined by the HSNO criteria. Not triggered Sub-class 6.5B – Contact sensitisation No information was located to indicate that Not triggered fluoropolymers would be contact sensitisers as defined by the HSNO criteria. PTFE has not been found to act as an allergenic agent. Polyvinyl fluoride tested negative for skin sensitization. Sub-class 6.6 – Mutagenicity No information was located to indicate that fluoropolymers would be mutagenic as defined by the HSNO criteria. Not triggered Sub-class 6.7 – Carcinogenicity No information was located to indicate that fluoropolymers would be carcinogenic as defined by the HSNO criteria. The International Agency for Research on Cancer (IARC) has classified PTFE as a class 3 substance [unclassifiable as to carcinogenicity to humans] i.e. not unclassifiable as a carcinogen under HSNO. Not triggered Sub-class 6.8 – Reproductive / developmental effects No information was located to indicate that fluoropolymers would be reproductive /developmental toxicants as defined by the HSNO criteria. Not triggered ERMA New Zealand section 26 determination HAZ03001 Threshold Page 3 of 19 Class / Sub-class Detail Threshold Sub-class 6.9 – Target organ systemic effects No information was located to indicate that fluoropolymers would be target organ systemic toxicants as defined by the HSNO criteria. A 90 day feeding study of rats with PTFE at levels up to 12500 mg/kg bw/day showed no signs of toxicity. A 10 month oral PTFE feeding study in rats showed no effect on the animals. Not triggered Class 8 – Corrosivity Fluoropolymers are not considered to be corrosive to metals (sub-class 8.1), to skin (sub-class 8.2) or to the eye (sub-class 8.3). Fluoropolymers are not listed in the UN Recommendations on the Transport of Dangerous Goods. Not triggered Class 9 - Ecotoxicity Fluoropolymers are not considered to be ecotoxic due to their low reactivity and high molecular weight. As such, they will not be bioavailable and therefore highly unlikely to adversely affect aquatic life (sub-class 9.1), soil organisms (sub-class 9.2) terrestrial vertebrates (subclass 9.3) or terrestrial invertebrates (sub-class 9.4). Although Fluoropolymers may not be rapidly biodegradable, they will not bioaccumulate due to their low bioavailablitiy. Not triggered Other information As discussed in the application form (attached as Appendix 1 to this document), fluoropolymers of molecular weight > 1,000 meet the USEPA polymer exemption rule and the NICNAS polymers of low concern criteria. Furthermore, various fluoropolymers are permitted by the US Food and Drug Administration (USFDA) “as articles or components of articles intended for use in contact with food” e.g. CFR Title 21 paragraphs 177.1380, 177.1550, 177.2510. ERMA New Zealand section 26 determination HAZ03001 Page 4 of 19 Recommended Determination If the Authority is of the view that fluoropolymers are not hazardous under the HSNO Act, then the Authority may: a) determine that fluoropolymers as defined are not hazardous pursuant to section 26 of the HSNO Act 1996; and b) direct the Chief Executive to arrange for notice of this determination to be placed in the Gazette. Dr Donald Hannah, Manager, Science and Analysis Date: 10 July 2003 Determination by the Authority The recommended determination is approved. Mr Tony Haggerty Chair Hazardous Substances Standing Committee Date: 30 July 2003 ERMA New Zealand section 26 determination HAZ03001 Page 5 of 19 Appendix 1 Application form HAZ03001 (attached) ERMA New Zealand section 26 determination HAZ03001 Page 6 of 19 ER-AH-O7-1 07/2001 FORM HS7 Application for applying for a determination under section 26 of the Hazardous Substances and New Organisms Act 1996 Use this form for making an application for the Authority to make a formal determination under Section 26 of the HSNO Act on whether or not a substance is hazardous. 1. Name and postal address of the organisation making the application: Name: Plastics New Zealand Address: P.O. Box 76378, Manukau City Phone: 09 262 3773 Fax: 09 262 3850 2. Name of the contact person for the application: Name: Joanna Wojnar Position: Scientific Advisor Address: P.O. Box 131, Wellington Phone: 04 918 4812 Fax: 04 914 0433 Email: Joanna.Wojnar@ermanz.govt.nz Page 8 of 19 Fluoropolymers Mw > 10,000 amu 1 Definition A family of polymers analogous to polyolefins in which some or all of the hydrogen atoms attached to the carbon chain are replaced by fluorine (and possibly other halides). Residual monomer, catalyst and solvent impurities <0.1%. Substances include: CAS number Structural formula CF 2 CF 2 n 900284-0 CH 2 CH F CF 2 CF n CF 2 CF 2 CF 3 m n Names Poly(tetrafluoroethylene) (PTFE), Teflon®, tetrafluoroethene homopolymer, Gore-tex®, perfluoroethylene polymer 2498114-4 Polyvinyl fluoride 2506711-2 Hexafluoropropene polymer with tetrafluoroethylene 2493779-9 Polyvinylidene fluoride 900283-9 Poly(chlorotrifluoroethylene) 2510145-5 Ethylenechlorotrifluoroethylene copolymer 901117-0 Vinylidene fluoridehaxafluoropropylene copolymer F CH 2 C F F n F C C F Cl n F CH 2 CH 2 F n F C C F Cl m F F C C CH 2 C F CF 3 n F m Page 9 of 19 2 Chemical and physical properties Appearance: White-greyish, translucent solid. Density: Varies, can range from 1.7 – 2.3 g cm-3 depending on monomer and branching. Melting point: Due to a range of molecular weights present in the polymer, melting points are actually broad ranges. Values can range from 170 - 340ºC depending on material. Solubility in water: Insoluble in water. 3 Introduction Fluoropolymers (the most famous one being poly(tetrafluoroethylene) or Teflon®) are characterised by good thermal and chemical resistance and non-adhesiveness. This is due to two factors: the fluorine/carbon bond is amongst the strongest known in organic compounds and the fluorine atoms repel other atoms and molecules. The combination of these two properties makes fluoropolymers extremely inert, unreactive, stable towards solvents and other chemicals, and very slippery1. These properties are exploited in applications such as non-stick cookware, ball bearings, piping, gaskets, containers that need to be chemically resistant, and also in human organ prostheses. 4 Hazard Classifications Class 1: Explosiveness – not triggered The fluoropolymers are not explosive as they pass the ‘screening procedures for substances which may have explosive properties’ as laid out in the User Guide to HSNO thresholds and classifications2 and they are not listed in the UN Recommendations on the Transport of Dangerous Goods3. Class 2: Flammable gases and aerosols – not applicable The fluoropolymers are solids. Class 3: Liquids and liquid desensitised explosives – not applicable The fluoropolymers are solids. They are not explosive. Class 4: Flammability – not triggered 4.1.1 – readily combustible In general, fluoropolymers are non-flammable1. They are also not listed in the UN Recommendations on the Transport of Dangerous Goods3. Page 10 of 19 4.1.2 – self-reactive The fluoropolymers are not self-reactive as they pass the ‘screening procedures for substances which may be self-reactive substances’ as laid out in the User Guide to HSNO thresholds and classifications2 and they are not listed in the UN Recommendations on the Transport of Dangerous Goods3. 4.1.3 – solid desensitised explosive Not applicable – fluoropolymers are not explosive 4.2 – spontaneously combustible The fluoropolymers are not spontaneously combustible as they pass the ‘screening procedures for substances which may be liable to spontaneous combustion’ as laid out in the User Guide to HSNO thresholds and classifications2 and they are not listed in the UN Recommendations on the Transport of Dangerous Goods3. 4.3 – dangerous when wet The fluoropolymers are not dangerous when wet as they pass the ‘screening procedures for substances which in contact with water may react to emit flammable gases’ as laid out in the User Guide to HSNO thresholds and classifications2 and they are not listed in the UN Recommendations on the Transport of Dangerous Goods3. Class 5: Capacity to oxidise – not triggered 5.1 – Oxidising substance not organic peroxide The fluoropolymers may contain the elements oxygen, fluorine, chlorine, but since they are only covalently bonded to carbon they will not have oxidising properties. 5.2 – Organic peroxide Fluoropolymers do not meet the definition of an organic peroxide. Class 6: Toxicity – not triggered Due to the high strength of the carbon/fluorine bond and the repelling properties of the fluorine atoms, the fluoropolymers are extremely inert physiologically and are in fact used for human organ prostheses4. 6.1 – Acute toxicity threshold: oral LD50 ≤ 5000 mg/kg Rats fed PTFE at a level of 12.5 g/kg showed no toxic effects5. The oral LD50 of the terpolymer (vinylidene fluoride-haxafluoropropylene-tetrafluorethylene) was >40 g/kg. Rats fed the vinylidene fluoridehaxafluoropropylene copolymer at 12.5 g/kg showed no clinical or nutritional signs of toxicity6. Page 11 of 19 6.3 – Skin irritant PTFE does not produce skin irritation5. Polyvinyl fluoride tested negative for skin irritation6. Skin irritation tests on the terpolymer (vinylidene fluoridehaxafluoropropylene-tetrafluorethylene) and the copolymer vinylidene fluoride-haxafluoropropylene produced only mild and transient responses6, insufficient to trigger HSNO thresholds. 6.4 – Eye irritant Eye irritation tests on the terpolymer (vinylidene fluoride-haxafluoropropylene-tetrafluorethylene) and the copolymer vinylidene fluoride-haxafluoropropylene produced only mild and transient responses6, insufficient to trigger HSNO thresholds. 6.5A – Respiratory sensitiser No specific data available 6.5B – Skin sensitiser PTFE has not been found to act as an allergenic agent6. Polyvinyl fluoride tested negative for skin sensitization6. 6.6 – Mutagen No specific data available 6.7 – Carcinogen While no animal studies have demonstrated that polytetrafluoroethylene is carcinogenic6, the International Agency for Research on Cancer (IARC) classifies PTFE and organic polymeric materials in general as Group 3 – not classifiable as to their carcinogenic effects5,7. Under HSNO they are therefore not classified as a carcinogen. 6.8 – Reproductive / developmental effects No specific data available 6.9 – Target organ systemic effects A 90 day feeding study of rats with PTFE at levels up to 12.5 g/kg bw/day showed no signs of toxicity5. A 10 month oral PTFE feeding study in rats showed no effect on the animals8. Class 8: Corrosiveness – not triggered 8.1 – Corrosive to metals Fluoropolymers are not listed in the UN Recommendations on the Transport of Dangerous Goods3 and there are no data to indicate that they are corrosive to metals. 8.2 – Corrosive to dermal tissue Fluoropolymers are not listed in the UN Recommendations on the Transport of Dangerous Goods3 and as they are not skin irritants cannot be corrosive to the skin. Page 12 of 19 8.3 – Corrosive to ocular tissue Fluoropolymers are not eye irritants and so cannot be corrosive to the eye. Class 9: Ecotoxics – not triggered As discussed under Class 6 – Toxicity, fluoropolymers are inert biologically, of high molecular weight and so are highly unlikely to adversely affect marine, soil or terrestrial vertebrates or invertebrates. Although they may not be rapidly degraded and so may persist in the environment, fluoropolymers are inert substances that are not bioavailable and hence will not bioaccumulate. 5 ERMA New Zealand classification The transfer group has already classified polytetrafluoroethylene as non-hazardous. 6 Foreign regulatory agencies guidelines: Fluoropolymers of molecular weight > 1,000 meet the USEPA polymer exemption rule and the NICNAS polymers of low concern criteria as listed in the appendix9. Furthermore, various fluoropolymers are permitted by the US Food and Drug Administration (USFDA) “as articles or components of articles intended for use in contact with food” (CFR Title 21 §177.1380, §177.1550, 177.2510). 6. Nature of determination sought: Whether the substance is hazardous under HSNO. CHECKLIST Yes Mandatory sections filled out Appendices enclosed Yes Fees enclosed (refer to Schedule of Fees and Charges on website www.ermanz.govt.nz) NA Application signed and dated Yes Signed Date Page 13 of 19 Appendix 7 General notes Limited specific data available Polymers, in the form of plastics and rubbers have been around for many years (1862 saw the first synthetic plastic – cellulose nitrate, 1931 the first synthetic rubber, neoprene). They have become ubiquitous in our daily lives as they have versatile properties. There has been widespread exposure to a variety of plastics over the years and very few reported cases of actual adverse effects. Plastics are therefore generally considered non-toxic and safe and consequently only very limited investigations have been carried out into the potential harmful effects of polymers. Explosiveness The organic polymers detailed in this application are not explosive as they pass the ‘screening procedures for substances which may have explosive properties’ as laid out in the User Guide to HSNO thresholds and classifications2. Flammability High molecular weight organic polymers are solid, non-explosive substances, and so the HSNO Class 2 (Flammable liquid), the HSNO Class 3 (Flammable liquid and liquid desensitised explosive) and HSNO Class 4.1.3 (solid desensitised explosive) will not apply. The organic polymers also pass the screening procedures for HSNO Classes 4.1.2, 4.2 and 4.3 as laid out in the User Guide to HSNO thresholds and classifications2. While most synthetic organic polymers will burn, just like the natural organic polymer of cellulose (found in wood/paper) when sufficient heat is applied to them, they are considered slow burning with some actually self-extinguishing or flame retardant. They will not be able to trigger the HSNO 4.1.1 readily combustible solid threshold. Toxicity, Ecotoxicity Polymers, by their very definition, are high molecular weight entities. Such large macromolecules are not able to cross lipid membranes into cells where the effects of toxic chemicals usually unfold. Polymers are therefore considered biologically inert as they are not bioavailable4,6, and are unlikely to trigger HSNO toxicity (Class 6) and ecotoxicity (Class 9) thresholds. Observed biological effects of polymers can be traced back to incompletely reacted monomer, solvents or other non-polymeric materials. Oral toxicity studies Overall toxicity of polymers is very low, the LD50 values are often above the limits of practical experimental testing6 and so will be above the HSNO Class 6.1 (acute toxicity) threshold. Indeed, adverse effects in long term animal feeding studies are most often the result of bulk amounts of polymer physically causing decreased food intake and so compromising the nutrition of the animal10 and not due to any target organ/systemic toxicity that may trigger HSNO Class 6.9. Page 14 of 19 General irritation Potential irritating effects of polymers to the respiratory tract, skin and eyes can be ascribed to physical action only10, which will not trigger HSNO Class 4 (skin irritation) and Class 5 (eye irritation) thresholds. Eye irritation Completely polymerised plastics that are free from small molecular weight compounds are generally inert. No toxicity to the eye is observed, except for such irritation as small foreign bodies cause when in the conjunctival sac or cornea11. Such physical effects will not trigger the HSNO Class 5 (eye irritation) threshold. Dust Most polymers are imported into the country in the form of pellets – too large to be an inhalation hazard. Some however, (for example PVC) may be of small enough size to be inhaled. Some cases of lung disease after prolonged exposure to PVC dust have been reported. The physiological response of the tissue to the dust is consistent with similar chronic exposures to other unreactive particulates as found, for example, in coal miners’ disease6. Limited data are available on the effects of other polymer dusts. Based on the low toxicity of polymers however, any adverse responses are most likely due to the physical presence of foreign particulate matter in the lungs. Such physical effects will not trigger HSNO Class 6.5A (respiratory sensitisation), Class 6.7 (carcinogenic effects) or Class 6.9 (target organ systemic effects). Proper industrial hygiene procedures should be followed around polymer dust, as around any other type of dust. Carcinogenicity Again due to their high molecular weight, polymers are highly unlikely to have carcinogenic or mutagenic effects. Some experimental investigations have shown that implantation of polymer material into subcutaneous, intraperitoneal, intramuscular and intrauterine tissue has resulted in some local sarcomas. Their incidence, however, is highly dependent on physical form of the implant. Roughening of the surface of the implant reduces the sarcoma incidence, often to nil with the segmentation or pulverisation of the material7. This is indicative of the so-called ‘solid state carcinogenesis’ which is critically dependent on the physical nature of the implant, rather than its chemical composition10,12. Overall, the International Agency for Research on Cancer (IARC) classifies organic polymeric materials as Group 3 – not classifiable as to their carcinogenic effects5,7, which means they are not classified as carcinogenic under HSNO Class 6.7. Solubility The majority of high molecular weight organic polymers are insoluble in water. This means they are effectively not bioavailable to aquatic organisms, and so will not have any HSNO Class 9.1 aquatic effects. Polymer exemption rule (Polymers of Low Concern) The US Toxic Substances Control Act (TSCA) of 1976 was enacted to test, regulate, and screen for any toxic effects, all chemicals produced or imported into the United States. In 1984 the Environmental Protection Agency (EPA) which administers the Page 15 of 19 Act identified certain criteria to determine which polymers were most unlikely to have any toxic or ecotoxic effects. These polymers were exempted from having to be notified to the Agency under the Polymer Exemption rule so established (Code of Federal Regulations Title 40 §723.250). A similar scheme has been adopted by the Australian National Industrial Chemicals Notification and Assessment Scheme (NICNAS), called “Polymers of Low Concern”. Both schemes recognise the inherent non-toxicity of high molecular weight molecules, with polymers above 10,000 amu exempt from reporting as long as they meet certain other criteria: 8 The oligomer content must be <2% of oligomers of size below 200 amu and <5% below 1,000 amu. The polymers must not be cationic or reasonably expected to become cationic in a natural aquatic environment as they may be able to cause a pH change and so be toxic to aquatic organisms. Residual monomer or impurity must not trigger any hazard thresholds The polymer must meet certain elemental criteria (restricting the types of elements permitted as an integral part of its composition). The polymer must be stable, i.e. it must not degrade, decompose or depolymerise substantially after manufacture and use. This does not include the slow, natural biodegradation. Polymers must not be water absorbing (i.e. capable of absorbing their own weight in water) due to the proven risk of lung damage after inhalation of water absorbing polymers. Lower molecular weight polymers may also be exempt, depending on the nature of their functional group – the less reactive the functional group, the lower the molecular weight requirement. Glossary of Terms H2C Acrylic/methacrylic esters: O O O R1 H2C O R1 CH3 Aliphatic hydrocarbon: a hydrocarbon with an open chain (acyclic) structure. Amide linkage: O R1 N R2 H Aromatic: having one or more benzene ring. Atomic mass unit (amu): exactly one twelfth the mass of a neutral atom of the most abundant isotope of carbon, 12C. 1 amu = 1.660 x 10-27 kg. Also called the Dalton. Carbonate linkage: O R1 O O R2 Page 16 of 19 Cationic /Potentially cationic: as defined in the NICNAS Synthetic Polymer of Low Concern Guidance Document. Copolymer: a polymer made of two different monomers. Engineering thermoplastics: thermoplastics used in structural or engineering applications, or in applications replacing metals. Usually have high strength and rigidity and maintain these properties over a broad range of temperatures. Ester R1 Ether linkage: O R1 O R2 O R2 linkage: Functional group: an atom or associated group of atoms with chemically active bonds. (Usually most things other than C-C or C-H single bonds). Heteroatom: in an organic compound, any atom other than carbon or hydrogen. Homopolymer: a polymer made up of only one type of monomer (neglecting the ends, branch junctions, and other minor irregularities). Hydrocarbon: a substance consisting only of carbon and hydrogen atoms. Monomer: a relatively simple compound which can react with other like or unlike monomers to form a chain; the basic building block of the polymer. Olefin (alkene): unsaturated hydrocarbon, of general formula CnH2n. Oligomer: low molecular mass polymer formed from two or more monomer units linked together. Polymer: a high-molecular-weight compound, natural or synthetic, characterised by the repeating sequence of one or more types of monomer units. R1/R2: generic alkyl group. Reactive functional group: a functional group that is intended or can be reasonably anticipated to undergo a facile chemical reaction. Terpolymer: copolymer of three different monomers. Thermoplastic: any resin which can be melted by heat, reshaped and then cooled. The process is in theory repeatable any number of times without a change in properties. Page 17 of 19 Thermoset: plastics which undergo chemical reactions (such as crosslinking) upon moulding which results in a vast network molecule, held together by covalent bonds, making the product resistant to further applications of heat (until the charring point). H H2C Vinyl group: C R R2 Vinylidene H2C C R1 group: Water absorbing polymer: a polymer capable of absorbing its own weight in water. 9 References 1 Know your plastics. Plastics Industry Association, 1992. 2 User Guide to the HSNO Thresholds and Classifications, ERMA New Zealand, 2001. Recommendations on the Transport of Dangerous Goods. Model Regulations. 12th ed. United Nations, Geneva, 2001. 3 Hamilton A. and H.L. Hardy. “Plastics” in Industrial Toxicology, Third Ed. Publishing Sciences Group, Inc., Acton, Massachusetts, 1974. 4 5 IARC Monograph 19, 1979. 6 Patty’s Industrial Hygiene and Toxicology. John Wiley & Sons, 2001. 7 IARC Monograph 74, 1999. 8 Sheftel, V. O. Indirect Food Additives and Polymers: Migration and Toxicology. Lewis publishers, 2000. 9 Polymer Exemption Rule, Code of Federal Regulations Title 40 §723.250. Drew, R. “Toxicity of plastics.” In Occupational Toxicology, N. H. Stacey, Ed.. Taylor and Francis Ltd. London, 1993. 10 Page 18 of 19 Grant, W. M. Toxicology of the Eye. 2nd ed. Springfield, Illinois: Charles C. Thomas, 1974. 11 Lewis, R. “Plastics” in Occupational Medicine, J. LaDou, Ed. Appleton and Lange, Norwalk, Connecticut, 1990. 12 Page 19 of 19