Waste/used crankcase oils priority substance list follow-up report: chapter 4

4. Effects characterization

In addition to previously existing reports (Ingersoll et al., 1993), new data identify constituents of used crankcase oils (UCO) (particularly the polycyclic aromatic hydrocarbons (PAHs), such as pyrene, fluoranthene and phenanthrene) as causal agents in the toxicity of sediment biota (Maltby, 1995a,b; Lefcort et al., 1997; Marsalek et al., 1997; Environment Canada, 1999; Forrow and Maltby, 2000). Following evaluation of these studies, the study by Ingersoll et al. (1993) is the basis for determining the Critical Toxicity Value (CTV).

Maltby et al. (1995a) investigated the effects of motorway runoff on the water quality, sediment quality and biota of small streams over a 12-month period in the United Kingdom. Sediment quality results indicated that the concentration of PAHs was elevated at all the sites receiving motorway drainage. Of seven streams sampled, macroinvertebrate biodiversity was reduced in four of the stations receiving road runoff of UCO. The reduction was significant only at a stream (Pigeon Bridge Brook) receiving drainage from a 1500-m stretch of the M1 motorway. A decrease in the number of macroinvertebrate taxa present in the stream below the motorway runoff discharge was observed. There was a loss of pollution-sensitive taxa below the motorway discharge and a change from an assemblage of benthic algae dependent on coarse particulate organic matter to one dependent upon fine particulate organic matter and dominated by taxa known as collectors. The diversity of the hyphomycete assemblage was significantly increased downstream of the discharge. Moreover, there was a significant reduction in the loss of leaf material from coarse-mesh bags deployed at the downstream station, suggesting an inhibition of leaf decomposition by macroinvertebrates. There was little evidence to suggest that changes in the physical structure of the habitat or reductions in the abundance of macroinvertebrate food sources were responsible for the observed changes in the macroinvertebrate distributions. However, subsequent investigations indicated that direct toxicity and contaminant-induced changes in food quality were important in determining macroinvertebrate abundance (Forrow and Maltby, 2000).

As a follow-up to this study, Maltby et al. (1995b) assessed the toxicity of sediments and water contaminated with motorway runoff to identify the group(s) of chemical compounds responsible for the observed toxicity. The experiments were concentrated on the benthic amphipod Gammarus pulex at the Pigeon Bridge Brook study site. Stream water contaminated with motorway runoff did not cause any harmful effects on G. pulex. However, exposure to contaminated sediments resulted in a slight but significant increase in mortality over 14 days, with a consistent 10.3% average mortality (experiment repeated three times) at the downstream site (compared with =5% mortality at the upstream control site). Sediment manipulation experiments indicated that most of the observed toxicity at the downstream site was due to the fraction containing PAHs.

Marsalek et al. (1997) collected samples of stormwater runoff from the James N. Allen Skyway Bridge in Burlington, Ontario, and analysed for five heavy metals and 14 PAHs in dissolved and particulate-bound phases. Dissolved-phase PAHs represented less than 11% of whole-water concentrations, while the remaining PAHs were bound to the particulate fraction of the highway runoff. While the results of the study indicated that heavy metals were the major pollutants, the authors indicated that there is the potential for chronic toxicity effects from PAHs in sediment due to their persistence in the sediment and continual addition of PAHs over time (Marsalek et al., 1997).

A 28-day flow-through sediment toxicity test was conducted on the benthic amphipod Hyalella azteca with whole sediment taken from the Clark Fork River in Montana (United States) and tested for effects due to 16 PAHs, including pyrene, fluoranthene and phenanthrene (Ingersoll et al., 1993). H. azteca is typically more sensitive than Chironomus riparius to contaminated sediments (Ingersoll and Nelson, 1990; Nelson et al., 1993). In this study, relative sensitivity (most sensitive to least sensitive) of test organisms was as follows: H. azteca > C. riparius > Oncorhynchus mykiss > Daphnia magna. The results of the 28-day whole-sediment toxicity tests indicated that phenanthrene, fluoranthene and pyrene caused significant harmful effects (95% mortality in mature adult males) on H. azteca at concentrations of 0.050, 0.083 and 0.083 µg/g dry weight, respectively (Ingersoll et al., 1993). H. azteca is also a relevant Canadian species. These values are very close to the Threshold Effects Level (TEL) that is used in developing the Canadian sediment quality guidelines for PAHs (Canadian Council of Ministers of the Environment (CCME), 1999). Using the modified U.S. National Status and Trends Program approach (Long and Morgan, 1991), TELs for pyrene, fluoranthene and phenanthrene have been calculated as 0.053, 0.111 and 0.0419 µg/g dry weight, respectively (CCME, 1999; Environment Canada, 1999).

Indirect effects of UCO were also recorded in the literature. One of four experiments by Lefcort et al. (1997) was a micromesocosm study in which 5-week-old salamander (Ambystoma opacum and A. tigrinum) larvae were placed in artificial ponds that were inoculated with plankton from the salamanders' native pond. Only one concentration of UCO (i.e., 100 mg/L) was tested aside from the control. Oil was added at monthly intervals to compensate for degradation after 13 weeks. After 13 weeks, the animals were sampled for length and weight, and the experiment was terminated shortly thereafter. Animals in the control treatment were larger than animals exposed to UCO and also had longer snout to vent lengths, longer total lengths and wider heads. The authors concluded that the toxicity was indirect, as the food source, i.e., algae, grew slower due to the presence of the oil, thereby affecting the size and weight of the salamanders.

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