Renewable hydrocarbons (naphtha type fraction)

Endpoint summary

Additional information

The substance is a complex mixture of hydrocarbon compounds with variable physicochemical and ecotoxicological properties. Application of standard ecotoxicological tests to such UVCB substances includes a number of technical problems such as low water solubility and volatility of the substance. Therefore no tests were conducted and no key information is available. However, information about terrestrial toxicity of fossil fuels is discussed based on literature. The read-across from fossil fuels is justified based on the similar composition and physicochemical properties compared with the renewable hydrocarbons of wood origin. The read-across justification is presented in annex 1 of the CSR.

A study by Trappet et al. (2001) determined 184-hour phytotoxicity using Salix viminalis and Salix alba to gasoline (95 ROZ). Test used transpiration, growth and water use efficiency as toxicity parameter. This study also included phytotoxicity tests using soil samples taken from former gas filling station. Results showed that in laboratory tests fresh gasoline at concentration of 1000 mg/kg was fatal to Salix viminalis and Salix alba and the trees were dead after 184 hours.

Dorn P.B. and Salanitro J.P. (2000) examined toxicity of soils (Norrwood and Norrwood/Baccto) spiked with crude oil (Light-Gulf of Mexico) and bioremediated for 9 and 11 months. Norrwood soil was silty loam obtained from cotton field near College Station, Texas, and contained 15 % clay, 60 % silt and 0.3 % organic carbon. The Baccto topsoil was commercially available sandy loam potting soil. Norrwood/Baccto soil mixture consisted 75 % from Norrwood and 25 % from Baccto soil (v/v) and contained 20 % clay, 56 % silt and 4.65 % organic content. Toxicity was examined by conducting 21-days plant growth and germination inhibition tests using corn (Zea mays), wheat (Tritium aestivum) and oat (Avena sativa). Results showed that in untreated soils, the plant seed germination was significantly decreased (50 -100 % inhibition) in all plants, but in bioremediated soils, seed germination was not significantly lower than in control soils. Plant growth was similarly reduced significantly in untreated soil, but although growth was enhanced in bioremediated soils, it was still 0-40 % lower compared to control soil.

In study by Labud et al. (2007), sandy soil (organic carbon content 5.7 %) and clayey soils (organic carbon content 13.8 %) were spiked with 5 % and 10 % (w/w) of gasoline and incubated in glass pots under controlled conditions (50-70% WHC and room temperature) for 180 days. During the study Microbial Biomass Carbon was used to evaluate toxicity response to microbes.

In conclusion, gasoline in soil at concentration of 1000 mg/kg has been shown to be fatal to trees (Trapp et al. 2001), but weathering can decrease the toxicological effects. In study by Salanitro J.P and Dorn P.B. (2000), weathered light crude oil (1000 mg/kg) in bioremediated soil (total organic content 0.3 %) reduced plant weight of corn, wheat and oat 16, 32 and 50 %, respectively, compared to control. Based on their result and findings from literature, Salanitro J.P. and Dorn P.B. (2000) suggested that hydrocarbon phototoxicity cannot be predicted and varies widely with oil and soil type, concentration and species tested. Labud et al. (2007) noticed that toxic response was slightly higher to microbes in sandy soils than in clayey soils. This was probably because the difference between the soil properties. Clay and organic matter are known to absorb contaminants and decrease their concentrations in aqueous and gaseous phase, and they also decrease their transport and bioavailability.

Soil toxicity tests for hydrocarbon substances have number of technical problems, such as water solubility and volatility. The fate and toxicity of these substances are also affected by weathering and aging of the fuel. Toxicity of UVCB in soil also depends from soil characteristics such as particle size, carbon content and soil texture also. Because of these problems, ecotoxicity tests for hydrocarbon contaminated soils don't always give direct correlation between concentrations and toxicity.