Johnson et al. (1993) showed that coexposure to UV-A between 300-400 nm enhanced the toxicity of nitrotoluenes to Phoiobacterium phosphoreum, a marine bioluminescent bacteria used in the Microtox test (Microbics Inc.). This paper reports that UV-A photoenhanced the toxicity of polynuclear aromatic hydrocarbons, other types of organic compounds, and some transition metals to P. phosphoreum. Coexposure to 400 μw/cm2 for 15 min increased the toxicity of psoralen, α-terthienyl, anthracene, acridine, fluoranthene,TNT, Cu2+, As3+, Ni2, and Cd2+. Phenanthrene was photoenhanced after 30 min coexposure at 400 μw/cm2+, and Mn2+ at 800 μw/cm2 aftef 15 min. Naphthalene was not enhanced at 800 μw/cm2 for 30 min Johnson et al. (1993) showed that coexposure to UV-A between 300-400 nm enhanced the toxicity of nitrotoluenes to Phoiobacterium phosphoreum, a marine bioluminescent bacteria used in the Microtox test (Microbics Inc.). This paper reports that UV-A photoenhanced the toxicity of polynuclear aromatic hydrocarbons, other types of organic compounds, and some transition metals to P. phosphoreum. Coexposure to 400 μw / cm2 for 15 min increased the toxicity of psoralen, α-terthienyl, anthracene, acridine, fluoranthene, TNT, Cu2 +, As3 +, Ni2, and Cd2 +. Phenanthrene was photoenhanced after 30 min coexposure at 400 μw / cm2 +, and Mn2 + at 800 μw / cm2 aftef 15 min. Naphthalene was not enhanced at 800 μw / cm2 for 30 min