Nitrification process involvesThis study revealed that IRK + FW microcosm was the most toxic (LC50) whereas LRK + BW microcosms was the least toxic. The inability of the organism to thrive well at kerosene concentration above 1% (v/v) is a warning signal of serious environmental pollution problem which could affect aquatic life forms and eventually humans. However, due to high fatality rate inherent from the use of LRK (though not reported here) and its toxicity to microbial life, it is hereby advocated that the public should rather resort to use IRK products.