Quaternary ammonium compounds, di-C16-18-alkyldimethyl, chlorides

Endpoint summary

Additional information

Quaternary ammonium compounds, di-C16-18 (even numbered) -alkyldimethyl, chlorides are poorly soluble in water and also have a strong tendency to adsorb to negatively charged surfaces such as suspended matter, vessels or organic material (including dissolved organic matter such as humic acids). Many cationic substances in general but long chain dialkyl quats in particular rank among the most difficult substances to test in environmental toxicology. Standard guideline studies are inappropriate to test substances with such properties and the current REACH Guidance Documents do not provide sufficient guidance concerning bioavailability and exposure assessment for cationic surface-active substances like the dialkylquats as these were written with normal hydrophobic chemicals in mind, failing to take into account the lack of bioavailability that occurs in the environment with these substances. Aquatic ecotoxicity tests performed in river water are therefore considered to assess the aquatic environmental risk more realistically for these difficult substances as the use of river water in the effect assessment compensates for the difficient prediction of the bioavailability in the exposure assessment.

Aquatic ecotoxicity tests performed in river water are therefore considered as higher tier tests when compared to aquatic ecotoxicity tests performed in reconstituted lab water. Aquatic ecotoxicity tests performed in river water were therefore selected to allow a PEC_{aquatic, bulk}/PNEC_{aquatic, bulk} approach. This is considered to be conservative but more environmentally realistic than the standard method. This approach is thus based on PEC estimations representing "total aquatic concentrations". To characterize the risk to the aquatic compartment the PEC_{aquatic, bulk} is compared with the PNEC_{aquatic, bulk} derived from river water ecotoxicity studies (ECETOC, 2001).

 In order to class standard laboratory toxicity study valid, it is of particular importance that - besides information on test substance, test method/conditions and test organism used - suitable precautions are taken to prevent the loss of test substance by adsorption and that exposure concentrations are based upon measured levels.

For ecotoxicity tests performed using the bulk approach, however, adsorption to suspended matter and DOC is acceptable and only adsorption to glassware should be accounted for. For a valid bulk approach test the concentration-effect relationship should be based on the sum of adsorbed and dissolved substance in the volume of the medium tested. One of the advantages of the bulk approach tests with these difficult substances is that in the presence of suspended matter and/or humic acids, the residual sorption to glassware will be negligible. The results of these bulk approach tests are therefore much easier to interpret, more environmental realistic, and if compared to PEC_bulkclearly provide a more appropriate assessment of risks for the environment.

Aquatic toxicity profile of Quaternary ammonium compounds, di-C16-18 (even numbered) -alkyldimethyl, chlorides

has been extensively reviewed and data are available for characterizing its possible ecological impacts at different levels of the trophic chain. Depending on the study, standard or river water was used that generated a high variability of results. The difference in different water qualities was most probably caused by adsorption losses and complexation with dissolved colloidal anionic surfactants and humic substances which may reduce bioavailability and thus the effective doses. When available, it is thus considered more relevant from an environmental point of view to use the toxicity value of studies carried out with river water based on the intrinsic properties of the substance. Indeed, the measured values in river water are generally related to the bulk concentration (which includes the fraction adsorbed onto suspended matter).

Short-term toxicity to fish:

Several studies were traced which demonstrate the toxicity of Quaternary ammonium compounds, di-C16-18 (even numbered) -alkyldimethyl, chlorides to

fish. Depending on species tested and experimental conditions (river water, well water and seawater) the LC50 -96h ranges from 0.29 to > 24 mg/L. The key study that has been selected was obtained in river water with a total organic carbon content of 4.6 mg/L and a LC50 -96h of 21.3 mg/L. LC50 -96h of 59.3 mg/L was obtained for marine fish, juvenile turbot, in artificial seawater.

Long-term toxicity to fish:

As for short-term toxicity tests, it has been noticed that toxicity was dependent on the experimental conditions. Embryo larval tests were conducted with Pimephales promelas in filtered well water and natural river water. In river water the NOEC for the most sensitive parameters hatchability and mean weight of larvae was 0.23 mg/L after 33 days test duration versus 0.053 mg/L in well water considering the most sensitive parameters (weight, lenght and larvae survival).

Short-term toxicity to invertebrates:

Acute toxicity to daphnids, like that for fish, varied with the type of dilution water used in the toxicity tests. In laboratory dilution water, the 48-h LC50 values for Quaternary ammonium compounds, di-C16-18 (even numbered) -alkyldimethyl, chlorides

ranged from 0.16 to 3.1 mg/L. The key value used was obtained in river water and was 3.1 mg/L. LC50 -48h was also obtained for marine invertebrate, the copepod Acartia tonsa and was calculated to be 3.3 mg/L that is very similar to value obtained for freshwater species.

Over all, based on these LC50 values, daphnids were more sensitive than bluegill to the surfactants.

Long-term toxicity to invertebrates:

The no observed effect concentration (NOEC) for daphnids exposed to 14C-labeled DSDMAC (considered as a good surrogate for DHTDMAC) in river water was determined to be 0.38 mg/L by Lewis and Wee in 1983. Length, total young and mean brood size of adults exposed to mean concentrations of >= 0.76 mg/L DSDMAC were significantly less (p <= 0.05) than the same parameters for adults in the controls and in the remaining test waters.

Toxicity to algae:

Many references are cited in the EU Risk Assessment DODMAC report (2002). The key study that has been selected was obtained in river water.

The corresponding NOEC value was 0.062 mg/L (EG & G Bionomics).

An other study (Kroon & van Ginkel, 1991) was carried out in accordance with the OECD 201 and properly assessed impact on growth rate but the test was not carried out in river water. The definitive algal growth inhibition test has been performed using the following nominal test concentrations: 0.04, 0.12, 0.36, 1.08 and 3.24 mg/L. The E_rC_{50 -}96 h and 72h ofQuaternary ammonium compounds, di-C16 -18 -alkyldimethyl, chloridesare 0.36 and 0.48 mg//L respectively. The E_rC₁₀and E_bC₁₀(72 h) are 0.13 and 0.11 mg/L respectively.

The acute toxicity of Quaternary ammonium compounds, di-C16 -18 (even numbered) - alkyldimethyl, chlorides was also evaluated with the marine algaSkeletonema costatumin a static test over 72 hours in accordance to the procedure described in EN ISO 10253:1998. EC50 -72h was calculated to be 0.24 mg/L and the NOEC determined was < 0.1 mg/L.

Toxicity to microorganisms:

Test results avaialble demonstrate that the microorganism toxicity derived in laboratory water tests has to be handled with care as a high influence of the composition of the wastewater (e.g. suspended particles, complexing agents) can be assumed, which is the same phenomenon as in surface water tests. Moreover the lowest PNECmicroorganisms of 0.043 mg/L seems to be unrealistic as it is reported that wastewater treatment plants operate at DHTDMAC concentrations of 3 to 8 mg/L. However, it is not documented whether the treatment process would be more effective without this DHTDMAC load in the influent and how less adapted plants might react. Nitrifying bacteria were found to be the most sensitive microorganisms with the lowest EC50 of 2.1 mg/L on which the risk assessment should be based (PNECmicroorganisms = 0.21 mg/L) to ensure that the most sensitive treatment process can take place.