Freshwater acute value

Final acute values for freshwater and saltwater organisms were determined to be 80.01 and 140.8 pg/L, respectively. Acute toxicity values determined from individual toxicity tests for freshwater and saltwater organisms ranged from 120.0 to 2,045 and 160 to 16,440 pg/L, respectively (U.S. EPA, 1993). 

Acute toxicity values (LC50) for freshwater organisms ranged from 55.7pgH for the amphipod Hyalella azteca) to 774 pgH for the snail Phy-sella virgata). No relationships have been demonstrated between water quality characteristics (such as hardness and pH) and toxicity. The freshwater final acute value (FAV) for NP is 55.7pgl which is equal to the LC50 for the most sensitive tested... 

Studies aimed at verifying this ratio have shown a 0.88 correlation coefficient for 11 freshwater species and 126 chemicals (Slooff et al., 1983). It was concluded on the basis of these results that compounds that produce acute toxicity also show chronic toxicity. Therefore, with the exception of substances with a very particular toxic action, it is possible to predict the chronic toxicity of a substance on a species based on the acute values obtained for the same compound with similar species (Giesy and Graney, 1989). 

Massachusetts Environmental toxicity values Freshwater Acute Chronic Marine Acute Chronic 20 gg/L 5.0 gg/L 300 gg/L 71 gg/L BNA 2001... 

Data available in the scientific literature were not sufficient for the calculation of Tier I acute or chronic WQC with other energetic compounds and their transformation products. Tier II secondary freshwater acute and chronic values (SAV and SCV, respectively) were derived by Talmage et al. [4] for TNB, 1,3-DNB, 3,5-DNA, 2-A-4,6-DNT, HMX, and RDX, by dividing the lowest genus mean acute value (GMAV) by the secondary acute factor (SAF Table 4.7). 

If data on a sufficient number and diversity of organisms are available, a final chronic value for a particular toxicant may be calculated in the same way that final acute values are determined. In practice, however, there are seldom sufficient data to allow a direct graphical estimation of the toxicant concentration that would exert a chronic stress on no more than 5% of the species in the system. In such cases an acute toxicity standard is established on the basis of an adequate amount of short-term toxicity tests, and an average acute/chronic toxicity ratio is then calculated on the basis of a smaller amount of information. The rationale for this procedure is that for a given pollutant the acute/chronic ratio is likely to be more constant between species than is the chronic or sublethal stress level itself Hence less information is required to estimate the acute/chronic ratio. The chronic toxicity standard is established by dividing the acute toxicity standard by the so-called final acute/chronic ratio. The EPA considers this procedure acceptable if acute/chronic ratios are available for at least three species and (a) at least one of the species is a fish, (b) at least one is an invertebrate, and (c) at least one is an acutely sensitive fi eshwater species or saltwater species when the ratio is being used to establish freshwater or marine criteria, respectively. 

An example of the calculation of a final acute/chronic ratio is shown in Table V for the pesticide dieldrin. Chronic values for this pesticide were available for only four species in 1980 when the guidelines for dieldrin were established (EPA, 1980a), and therefore it was necessary to use acute/chronic ratios to estabhsh the final chronic value. Acute toxicity values were available in only three of the four cases where chronic effects were studied, but the three species satisfied the criteria for calculating acute/chronic ratios in both freshwater and salt water. Since the acute/chronic ratios for the three species differed by less than a factor of 2, it was appropriate to calculate the final acute/chronic ratio for dieldrin by taking the geometric mean of the three ratios, which is [(11)(9.1)(6.2)] / = 8.5. Final acute values for dieldrin in freshwater (EPA, 1996b) and salt water are 0.48 and 0.71 ppb, respectively. Hence the final chronic values for dieldrininfreshwaterand saltwater areO.48/8.5 = 0.056 ppb and 0.71/8.5 = 0.084 ppb, respectively. 

Under the present system (EPA, 1996b), the two numbers in the criterion are calculated from the final acute value, the final chronic value, and the final plant value. The three values for dieldrin in freshwater and salt water are shown in Table VII. The criterion maximum concentration is equated to half the final acute value. Division by 2 in this case to some extent corrects for the fact that much of the acute toxicity information is based on observations of lethal effects, whereas the real concern is protection of organisms fi om sublethal stresses. The criterion continuous concentration is the smaller of the final chronic value and the final plant value. 

In practice, there will sometimes be situations for which saltwater toxicity data are not available. In these situations, it may be deemed necessary to use freshwater data in lieu of data for marine species. However, several regulatory authorities (e.g., Australia, Canada, and the United States) would not extrapolate from freshwater data to set a definitive marine EQS. Based on acute SSDs, Wheeler et al. (2002) concluded that it is possible to use freshwater toxicity data to extrapolate to saltwater effects by applying an appropriate assessment factor. However, they did not propose a value for this factor moreover, looking in detail at their results (see Section 4.6.1), this extrapolation could be overprotective in some cases. 

Our consensus is that if a marine (acute or chronic) EQS is needed, then it should be based on experimental marine data and not extrapolated from freshwater studies. If data are substituted from freshwater systems to marine (or vice versa), the proposed standard should only be considered as tentative (see Zabel and Cole 1999). A tentative value of this type is likely to be unreliable if used for regulation. 

Treatment of cherry-mazzard hybrid seeds with acenaphthene powder for 10 h inhibited the seed germination and seedling growth. Treatment of Allium cepa root meristem cells with acenaphthene vapor for 12-96 h caused anomalies leading to random development of cells. Acute toxicity value for bluegill fish was 1700 in freshwater and the toxicity... 

Atrazine, with acute oral LD50 values of >900 mg kg , is practically nontoxic to birds. The compound is slightly toxic to aquatic animals. Rainbow trout and midge, the most sensitive freshwater species tested, have 96 and 48 h LC50 values of... 

The US EPA ECOTOX database reports that Cer-iodaphnia and Daphnia species are the most sensitive freshwater organisms following acute (48 h) exposure to benzene, with respective EC50 values of 130 and 400 ppb. Most organisms, however, can tolerate acute concentrations higher than this (in the 1-10mgl ... 

Due to the potential for release to aquatic environments, considerable work has been done on evaluating the aquatic toxicity of BPA. Acute toxicity (96 h LC50 values) for freshwater organisms ranged from 4.6mgl for the fathead minnow Pimephales promelas), to 9.4mgl for the Atlantic silverside (Menidia menidia). 

---