We examined acute toxicities of ten nitrated polycyclic aromatic hydrocarbons (nitro-PAHs:1-nitronaphthalene, 2-nitrofluorene, 3-nitrofluoranthene, 1-nitropyrene, 6-nitrochrysene, 1,5-dinitronaphthalene, 2,7-dinitrofluorene 1,3-dinitropyrene, 1,6-dinitropyrene, and 1,8-dinitropyrene) for marine organisms at three trophic levels, viz., the diatom Skeletonema costatum, the crustacean Tigriopus japonicus, and two species of fish, Fundulus heteroclitus and Pleuronectes yokohamae. We were able to estimate acute toxicity values of three nitro-PAHs for S. costatum, five nitro-PAHs for T. japonicus, three nitro-PAHs for F. heteroclitus, and one nitro-PAH for P. yokohamae. The most toxic nitro-PAHs were 1-nitropyrene for S. costatum (average 72-h median effect concentration: 0.53μg/L), 1,6-dinitropyrene for T. japonicus (average 24-h median effect concentration: 3.5 μg/L), 3-nitrofluoranthene and 1-nitropyrene for F. heteroclitus (average 96-h median lethal concentration: 170 μg/L), and 1-nitronaphthalene for P. yokohamae (average 96-h median lethal concentration: 770 μg/L). We also estimated predicted no effect concentrations (PNECs) of nitro-PAHs. The PNECs of 1-nitronaphthalene, 2-nitrofluorene, 3-nitrofluoranthene, 1-nitropyrene, 6-nitrochrysene, 1,5-dinitronaphthalene, 2,7-dinitrofluorene, 1,3-dinitropyrene, 1,6-dinitropyrene, and 1,8-dinitropyrene were 5,600, >46, 17, 4.2, >0.33, >380, >8.6, 130, 33, and 41 ng/L, respectively. The information on environmental concentrations of nitro-PAHs is inadequate, environmental risk assessment awaits further research.

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Rapid and simple screening method is required for a first step of determining effects of chemicals or assessing effluent toxicity of wastewater from industry or disposal site. A screening growth inhibition test method using salt water plankton Dunaliella sp. is developed. The alga is incubated at 21 ± 0.5 °C using 50 mL Erlenmeyer flask for the test vessel with air-permeable stoppers and without shaking. Biomass is determined by cell counting with an electronic particle counter. An exponential growth of the alga was observed over 72 h, and reproducible results were obtained from 12 repetitions of growth test. The average specific growth rate for 72 h is 1.62 ± 0.03 d^-1（mean ± SD）for controls. The alga was treated with eight chemicals for 72 h. Growth rates was calculated, and a 50 % inhibition of growth rate（ErC ₅₀）is determined. The sensitivity of the algae was compared with a most popularly used alga Pseudokirchneriella subcapitata（green alga）using 72 h-ErC₅₀. The alga was more sensitive to some chemicals than P. subcapitata and not to other chemicals. In this screening test using the algae, the 72 h-ErC₅₀ values of chemicals tested were nearly equal to the 48 h- or the 24 h-ErC₅₀ values. This meant a possibility of rapid testing for only 24 h exposure instead of conventional 72 h as screening testing.

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