Summary Report: NA/154

HWS-130

MBT (Australia) Pty Ltd, 11 Stanton Street, Seven Hills NSW 2147 has applied for an Assessment Certificate for the importation of the chemical, "HWS-130", under section 23 of the Industrial Chemicals (Notification and Assessment) Act 1989. HWS-130 is intended to be used as a binder in construction materials.

Physical and Chemical Properties

At normal temperature and pressure HWS-130 is a resin like brown liquid with a slight odour. It has a density of 1.12 x 10³ kg/m³ (25 ^oC), a vapour pressure of 25 Pa (25 ^oC), a surface tension of 51.6 mN/n (20 ^oC), a viscosity of 100 mPa.s (20 ^oC) and a water solubility of 0.56 g/L (20 ^oC). Estimates of fat solubility and partition co-efficient (log P_ow) are 5000 mg/100 g solvent and > 3.3 respectively. HWS-130 has a flash point of 66 ^oC and an autoignition temperature of 345 ^oC. It is not flammable or explosive, and is not expected to be an oxidizer.

Assessment of Toxicological Data

HWS-130 was found to have low acute oral and dermal toxicity, to be non-irritating to the skin, and a non-sensitizer but was observed to be slightly irritating to the eyes. It was not mutagenic towards Salmonella typhimurium, nor was it clastogenic towards polychromatic erythrocytes of mouse bone marrow in vivo. HWS-130 was found to be a clastogen in vitro in the V79 cell line of the guinea pig when used in concentrations that reduced the mitotic index to below 50%. In rats, the target organ for toxicity was the liver following repeated dosing for 28 days.

Assessment of Public and Occupational Exposure and Health and Safety Effects

The notified chemical is an acrylic monomer which will be used as a binder in construction materials such as plaster and mortar. It will be blended with other acrylic monomers and marketed as Part A of a two part mix. HWS-130 is a liquid with a low vapour pressure. It is therefore unlikely to be easily inhaled nor splashed.

Toxicological studies suggest that the risks associated with HWS-130 pertain to its slight eye irritancy and liver damage with repeated oral exposure. These results indicate that care needs to be taken at all times to minimise contact with the substance. A test performed to detect mutagenicity gave negative results. The notified substance had clastogenic effects in an in vitro assay using mammalian cells, however these effects were observed only at high cytotoxicity and moreover an in vivo clastogenicity assay was negative.

Only a small number of workers will be using the raw product. The formulated products which are resinous in nature will be used by numerous construction workers who will be mixing it with another substance to cure the formulation containing HWS-130. Due to the low vapour pressure, the most likely route of exposure is expected to be dermal. Care will be required to prevent HWS-130 from entering the body via this route.

Provided that reasonable care is taken to avoid skin and eye contact it would appear that HWS-130 will not pose a serious hazard to those who use the product and under normal use conditions would not pose a significant risk to health.

The public will be exposed to HWS-130 in formulated products, mainly in the form of skin, and possibly eye contact, during the mixing and curing process. It is considered that HWS-130 will not pose a significant hazard to health when used in the appropriate manner.

Assessment of Environmental Fate

HWS-130 has moderate water solubility (560 ppm). Therefore leaching from landfill sites may occur if the chemical is released in an uncured form. Incineration of the notified substance is expected to produce oxides of carbon and nitrogen. There is a very low potential for exposure of the unreacted monomer to the environment from the proposed use.

Since it contains ester groups HWS-130 is likely to hydrolyse, either chemically or biologically, under environmentally relevant conditions. Tests indicated that the chemical was unstable at neutral and basic pH. The biodegradation of the notified chemical was measured (28 day) using the modified Sturm test (OECD Guideline 301B) and classified as not readily biodegradable. Under the stringent test conditions, the degree of degradation was indicated as 38% and 26% for concentrations of 10 and 20 ppm respectively. While the chemical did not pass this stringent test, significant levels of biodegradation are likely under environmental conditions.

Based on the molecular structure, relatively high water solubility and hydrolysis/metabolism potential of HWS-130, bioaccumulation is considered unlikely.

The HWS-130 is not expected to be released to the environment until it has been fully cured as part of the coating formulation. Therefore the monomer will be effectively immobilised, chemically bound within the resultant polymer matrix. In the cured form leaching from landfill is not expected.

Assessment of Environmental Effects

The acute toxicity of HWS-130 to carp (Cyprinus carpio) and daphnia was assessed. Results indicate a nominal 96 hour LC₅₀ for carp of between 18 ppm (0% mortality) to 56 ppm (100% mortality). The 48 hour EC₅₀ for daphnia immobilisation was estimated between 100 and 180 ppm.

Assessment of Environmental Hazard

HWS-130 may be classed as slightly toxic to aquatic species based on the acute toxicity studies on carp and daphnia. The solubility of the monomer is sufficiently high to allow release to the aquatic compartment in the event of inappropriate use. However, the current usage pattern indicates that release of the uncured material to the aquatic compartment is unlikely and the associated hazard is negligible.

The notified chemical is not expected to be released to the environment until it has been fully cured and chemically bound within a polymer matrix. The ultimate fate of all cured material is landfill. Leaching of the notified chemical from cured material in landfill is not expected due to the chemical and physical bonding which occurs during the surface coating process. The potential for release to the aquatic compartment is minimal.

The low level environmental exposure of the notified chemical as a result of normal use indicate that the overall environmental hazard should be negligible.

Recommendations

To minimise occupational and environmental exposure to HWS-130 the following guide-lines and precautions should be observed:

• If engineering controls and work practices are insufficient to significantly reduce exposure to a safe level, then personal protective devices which conform to and are used in accordance with Australian Standards (AS) for eye protection (AS 1336; AS 1337) (13,14), impermeable gloves (AS 2161) (15) and protective clothing (AS 3765.1 AS 3765.2) (16,17) should be worn.
• Good work practices should be implemented to avoid spillages.
• Good personal hygiene should be adopted.
• A copy of the MSDS for products containing the notified monomer should be easily accessible to employees working with products containing the chemical.
• For best practice, the notified chemical should be polymerised prior to disposal (landfill or incineration).

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