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Multiple reliable studies are available for two freshwater species of fish.  Two acute toxicity studies are available for rainbow trout (Salmo gairdneri) establishing LC50 values of 11.2 and 13g/l respectively.  Whilst the latter was from a 96 hour study, the former was from a 24 hour flow through acute toxicity study. Whilst the test duration is shorter than normally required, data from other studies suggests that the toxicity does not increase significantly between 24 and 96hrs.  This study is not regarded as the key study but the result is used to derive the LC50 for this species.  Multiple studies are also available for fathead minnows (Pimephales promelas).  Those studies that were not limit tests established LC50 values of 13.5, 14.2 and 15.3g/l.  Two of these were flow through studies using analytical rather than nominal concentrations.  This data is consistent in demonstrating that the acute LC50 for fish is well in excess of 10,000mg/l.  In a study which approximated to an OECD212 Embryo and Sac-fry stage test, ethanol was found to exhibit a no effect level of 1000mg/l or more for most end points. However, for the end point of shortening of motoneuron axons (the study was specifically interested in neurotoxicity end points) a lower NOEC of 250mg/l was observed. Long term tests are expected to cover all stages of the life cycle to give an accurate estimate of chronic toxicity. It is therefore expected that the embryo and sac fry test would be less sensitive than a full early life stage test. However, for substances with a log Kow <4 that have a non specific narcotic mode of action (such as ethanol) the difference in sensitivity between the two tests would be expected to be small. An OECD 212 study can therefore be considered as an appropriate protocol to assess the long term toxicity of ethanol to fish.

There are a large number of studies available providing ethanol toxicity data for invertebrates for both fresh and saltwater species. Freshwater species for which there are data include Daphnia magna, Ceriodaphnia dubia, Daphnia pulex, Streptocephalus proboscideus, Brachionus calyciflorus, Gammarus fasciatus, Asellus intermedius, Heliosoma trivolvis and Dugesia tigrina.  Data for a number of these are however only from limit tests up to 100mg/l and some are from studies carried out for only 24 hours.  48hr EC50 values are only available for the first two species.  The critical value (lowest EC50) value is derived from a reliable 48 hour acute toxicity study carried out to an ASTM protocol where Ceriodaphnia dubai were exposed to ethanol at sufficient concentrations to enable an EC50 value of 5012mg/l to be calculated based on an end point of mortality and as a geometric mean of 3 separate replicated assays.  Saltwater species for which there is data include Artemia salina and Brachionus plicatilis.  48hr toxicity data is only available for the former and this study provide the lowest EC50 value for saltwater species.  In this reliable 24 hour acute toxicity study, Artemia Salina (brine shrimp) were exposed to ethanol at sufficient concentrations to enable EC50 values to be established. The study looked at shrimp nauplii of ages 24, 48 and 72 hours to assess for variation in sensitivity versus age. An EC50 of 1833mg/l was established for the 24 hour old nauplii based, however lower values of 858 and 695mg/l were established for the 48 and 72hr old nauplii respectively. (Whilst different, the two lower results were not statistically significantly different.) The results suggest that older specimens of this species are more sensitive than the younger ones. It should however be noted that in another 24 hour acute toxicity study using the same species at geometrically spaced concentrations up to 10,000mg/l under static conditions, a TLm (50% mortality) was not established at the maximum dose tested of 10000mg/l. There are also multiple studies on the chronic toxicity of ethanol to invertebrates covering the species Ceriodaphnia dubia, Daphnia Magna and Palaemonetes pugio. The lowest no effect levels were seen with the two daphnia species. In a very well reported invertebrate reproduction study, Daphnia magna were exposed to ethanol over a period of approximately 10 days, sufficient for the production of 3 broods of offspring. An LC50 of 454mg/l was reported for the adults but a much lower NOEC of 9.6mg/l was reported for the reproduction test, based on criteria of total progeny, number of broods and mean brood size. In the same study, Ceriodaphnia dubia were similarly exposed. An LC50 of 1806mg/l was reported for the adults and the same NOEC of 9.6mg/l as for the D magna and based on the same findings.  A very low NOEC of 2mg/l was reported for the Ceriodaphnia adults, but it was unclear what exact end points were used for this or why this figure was so much lower than the LC50. For this reason, the NOEC for this study is based on the reproduction end point.

There are again multiple studies covering a large number of algal species, both fresh and salt water. Freshwater species for which there is reliable data include Chlorella vulgaris, Selenastrum capricornutum, Chlamydomonas eugametos, Scenedesmus obliquus, Gleocystis ampla:, Nannochloris sp, Tetraselmis sp, Chlorella elipsoida and a Chlorococchus sp. As with the invertebrate data, a number of these were assessed in limit studies, albeit ones with quite high maximum concentrations tested. Chlorella proved to be by some margin the most sensitive species.  In a study which followed the basic principles of a guideline study, the green algae Chlorella vulgaris was exposed to ethanol at sufficient concentrations to enable EC50 values to be established. Exposure was carried out over 5 days with daily measurements of growth characterised by chlorophyll measurement. The dose response curve obtained was very shallow. The four day data presented showed some evidence that the control had passed the exponential growth phase. Basing the results on the 3 day measurements when exponential growth was still clearly evident, ethanol showed toxicity to the Chlorella species.  The EC10 (72hr) value was= 11.5mg/l and the EC50 (72hr) value were 275mg/l.  It should be noted that the next most sensitive species (S capricornutum, examined in the same study, was able to tolerate concentrations of 40x that of Chlorella.)  Saltwater species for which there is reliable data include: Skeletonema costatum, Cyclotella sp, Cylindricotheca sp, Navicula sp, Thalassiosira weissfigii, Nitzschia pusill, and Nitzschia species.  Again, a number of these were assessed in limit tests.  The Cylindricotheca species proved to be the most sensitive.  In this study for which only basic results are available, ethanol caused growth inhibition in a Cylindricotheca species, with a NOEC of 1580mg/l and an EC50 of 1970mg/l.  Whilst one species of algae was found to be quite sensitive to ethanol, the number of algal species tested confirms that this is result was unusual and that toxicity of ethanol to algae is in general quite low.

There is experimental data available on the toxicity of ethanol to aquatic plants available (Lemna species).  In a well reported study that was carried out to guideline, five species of duckweed (Lemna gibba and 4 clones of Lemna minor, 6591, 7010, 7102 and 7136) were exposed to ethanol over a concentration range of 1 to 21000mg/l over a 7 day period.   The lowest results (EC50 of 5967mg/l, NOEC of 1296mg/l were obtained with Lemna gibba, which also showed lower variability in the values, and is therefore used as the key study.

A number of studies have been carried out to assess the toxicity of ethanol to micro-organism using multiple species of protozoa and bacteria in fresh water.  These include Pseudomonas putida, Paramaecium caudatum, Uronema parduczi, Chilomonas paramecium, Entosiphon sulcatum and Tetrahymena pyriformis. These reliable studies indicate that the substance may be slightly toxic to micro-organisms. The weight of evidence suggested that the substance is generally of low toxicity.  Toxicity to P. Putida is frequently used as a standard method for assessing toxicity to micro-organisms.  This produced results around the middle of the those obtained for all species Ciliated protozoa are acceptable as surrogates to predict the toxicity in a WWTP; Paramecium meet this criteria but not Entosiphon.  The result for Paramecium (EC50 =5800mg/l) indicates that this is the most sensitive micro-organism that is representative of micro-organisms found in waste water treatment plants.