Abstract
Lemna sp. growth inhibition test standardized protocols suggest the use of compounds such as 3,5-dichlorophenol as reference substances for checking the test organism’s sensitivity routinely. However, this and other recommended chemicals present risks to human health and to the environment. Sodium chloride (NaCl) appears as a less toxic alternative reference substance which has been successfully used in routine ecotoxicological tests. However, the evaluation of this compound in multiple growth endpoints used in the L. minor test, which is required for recommending it as a reference substance for this test organism, has not yet been reported. In the present study, NaCl was tested with L. minor for the growth endpoints frond number, total frond area and fresh weight. Results showed acceptable sensitivity and reproducibility (coefficient of variance < 15.0%) for all three of the measured endpoints. Statistically significant differences were observed between the EC50 values calculated based on the three endpoints (p < 0.05). Total frond area was the most sensitive one, with average EC50 value of 2742.80 ± 245.7 mg L-1. It was anticipated that NaCl can be a suitable alternative reference substance and that total frond area should be the endpoint of choice for sensitivity toxicity tests using NaCl.
Highlights
Reference substances are standard chemicals used to assess organisms’ sensitivity in ecotoxicological tests and to establish essential test conditions for each species (Zagatto, 2008; Amorim et al, 2012)
We have expanded the results published in the literature regarding the NaCl toxicity for L. minor, since we have evaluated additional endpoints neglected in routine tests, such as total frond area and fresh weight
The results presented in this study show that NaCl can be a suitable alternative reference substance for routine toxicity tests using L. minor since the tests performed with this salt presented acceptable sensitivity and reproducibility, measured in multiple growth endpoints
Summary
Reference substances are standard chemicals used to assess organisms’ sensitivity in ecotoxicological tests and to establish essential test conditions for each species (Zagatto, 2008; Amorim et al, 2012). They are used to assess the precision and reliability of data obtained by a laboratory for the selected reference toxicant (Canada, 2007). The use of alternative substances is necessary in order to avoid unnecessary risks to human health
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