On the toxic effects of tetraethyl lead and its derivatives on the chrysophyte Poterioochromonas malhamensis: I. Tetraethyl lead

Abstract

The influence of illumination and aeration on the behavior of the antiknock additive tetraethyl lead (TEL) in aqueous media and on its toxicity to cultures of Poterioochromonas malhamensis was studied. Based on the results of these investigations the following conclusions were drawn: (i) In darkness TEL is not toxic to the algae, even at extremely high concentrations. (ii) Depending on TEL concentration, the growth, mitosis, and cytokinesis of the cells are inhibited in illuminated cultures, resulting in the formation of giant cells. (iii) TEL is converted to a highly toxic derivative by light in the presence as well as in the absence of living cells. Therefore it is concluded that Poterioochromonas is not able to metabolize TEL to the toxic agent. (iv) The photolytic toxification of TEL can be detected after as little as 3 to 6 hr of incubation in the light. Maximal toxicity is reached after 24 to 32 hr of illumination. (v) Free radicals, which can be formed by photolysis of TEL, seem to play no or only a minor role in TEL toxicity to Poterioochromonas. (vi) Due to its low water solubility and its high air solubility and volatility, TEL is cleansed from the cultivation media by aeration. This process seems to be completed after 2 to 3 days of aeration in darkness. In the light, however, this process is counteracted by the photolytic creation of a more stable, water-soluble, and nonvolatile TEL derivative which accumulates with time and which is responsible for the toxic effects. (vii) Very probably this toxic TEL derivative is identical to triethyl lead.