Isooctyl acrylate

Endpoint summary

Additional information

In the EU, isooctyl acrylate (IOA) is used as a monomer for the formation of adhesive and light-cured printing ink polymers. It is a very reactive monomer and is rapidly polymerized in its uses. Risk management measures include destruction of product and wastes containing unreacted monomer via incineration. All 3M manufacture of IOA in the EU will be at a location where biological wastewater treatment coupled with carbon treatment is applied to wastewater. The industrial sludge from the manufacturing process is incinerated and therefore direct exposure to soil from application of sewage sludge will not occur. Downstream facilities that use unreacted IOA monomer may contain treatment systems to control atmospheric emissions and have no IOA emissions to water from their uses. The STP sludge from the incineration facilities is also incinerated, not land-applied.

IOA is a UVCB material comprising a mixture of mostly branched alkyl esters of acrylic acid. The average number of carbons in the esterified alcohol unit is approximately eight, with the material as manufactured consisting of mostly (>94.0%) C8 esters and smaller amounts of C7 and C9 esters. The properties of this material are therefore averages. This material is moderately volatile (vapor pressure of 0.8 mm Hg at 20°C) and has a low water solubility (12.44 mg/L at 23 °C). A Henry's Law constant of 1780 Pa*m³/mol at 23 °C, calculated using experimental values, indicates a tendency to volatilize from aquatic systems or moist environments. The vapor pressure indicates that IOA released to the atmospheric compartment will remain in the vapor phase. Vapor-phase IOA is expected to degrade quickly due to indirect photolysis, with a half-life of 1.45-1.78 days.

IOA is readily biodegradable, with >67% biodegradation after 15 days and 93-95% after 28 days (OECD301D assay). Abiotic hydrolysis is not expected to contribute significantly to fate within this timeframe. Material released to wastewater treatment systems or surface waters would be rapidly degraded.

In an HPLC study designed to estimate the octanol-water partition coefficient, nine peaks having a range of partition coefficients of 4.0 to 5.0 were reported, with major peaks (those contributing ≥5% of total peak area) having a range of 4.5-4.7. The constituents of IOA therefore have partition coefficients in the range of chemicals having a potential to bioaccumulate and further evaluation was needed. No experimental studies of bioconcentration of IOA were available. In a QSAR analysis using Catalogic software v.5.10.9, BCF values ranging from 120 to 940 were predicted for fish. This software establishes a baseline BCF based on log Kow and applies factors for metabolism, a conformation-based calculation of molecular size, water solubility, and presence of phenolic or acidic functional groups. Metabolism of acrylate esters in mammals is well studied. It is shown that metabolism is via ester hydrolysis and is nearly complete. Acrylate esters are rapidly detoxified and eliminated. Hydrolysis of acrylate esters is not considered by the applied QSAR model. Therefore, the QSAR provides an extremely conservative estimate of bioconcentration potential for IOA. Nevertheless, predicted BCF values remain less than 2000.

The log adsorption coefficient (log Koc) was found to range from 2.81 to 3.59 L/kg, with the single predominant component (93% of total peak area) having a log Koc of 3.18. This indicates that IOA would sorb strongly to soil, sediment or activated sludge and would have little mobility in soil. Though readily biodegradable, reduced water availability relative to aquatic systems and sorption of IOA to soil organic matter would slow the process of removal.

Summary: IOA is quite reactive and will be polymerized rapidly in industrial applications. Most emissions will be to air rather than to water. IOA released to the atmosphere will be rapidly destroyed by indirect photolysis. Any IOA released to water will be rapidly biodegraded. It is not expected to bioconcentrate to levels of concern. Releases to soil are indirect due to deposition from the atmosphere and are expected to be low. IOA will likely sorb to soil and be slowly biodegraded.