MICROTOX EC50 VALUES FOR DRINKING-WATER BY-PRODUCTS PRODUCED BY OZONOLYSIS

The aim was to determine the Microtox EC50 values of some aliphatic aldehydes and carboxylic acids of normal chain length with 1-14 carbon atoms since these compounds have been detected as ozonolysis by-products in drinking water. The aqueous EC50 values decreased with increasing chain length except for formaldehyde and for the C1-C7 acids. At chain lengths above C7, where methanolic saline solutions were utilized to promote solubility, the aldehydes were more toxic than their corresponding carboxylic acids. Below a chain length of C7, the reverse situation applied. More precise and sensitive EC50 values were reserved at 15 and 25 min than at 5 min. Both C14 aldehyde and acid as well as palmitoleic acid showed luminescence in methanolic saline solutions. The C14 compounds are known natural substrates for bacterial luciferase, and the present findings confirm this for Photobacterium phosphoreum. The concentrations of the aldehyde and/or carboxylic acid ozonolysis by-products reported in drinking water could not be detected by the Microtox test. This is the first report of Microtox EC50 values for these carboxylic acids and for aldehydes of chain lengths > C4. © 1992.