LAUSR

Chlorination is commonly used to control biofouling organisms, however, chlorine rapidly hydrolyses in seawater to hypochlorite which undergoes further reaction with bromide, then with organic matter. These reaction products collectively termed chlorine-produced oxidants (CPOs) can be toxic the marine biota. Because the lifetime of the most toxic forms is limited to several days, appropriate guideline values (GVs) need to be based on short-term (acute) toxicity tests, rather than chronic tests. Flow-through toxicity tests that provide continuous CPO exposure are the most appropriate, whereas static-renewal tests generate variable exposure and effects dependent on the renewal rate. Literature data for acute CPO toxicity from flow-through tests together with values from two sensitive 15-min static tests, comprised 30 species from 9 taxonomic groups. These values were used in a species sensitivity distribution (SSD) to derive GVs that were protective of 99, 95 and 90% of species of 2.2, 7.2 and 13 µg CPO/L respectively. These are the first marine GVs for chlorine to be derived using SSDs, with all other international GVs being of unknown reliability being based on the use of assessment factors applied to data for the most sensitive species. In applying these conservative GVs in field situations, it would need to be demonstrated that concentrations of CPOs would be reduced to below the GV within an acceptable mixing zone both through dilution and dissociation. This article is protected by copyright. All rights reserved.