TINY plants and animals at the bottom of Victoria and Tolo harbours contaminated by chemicals are to be studied and results could point to potential health risks for humans. Overseas studies have found women eating fish contaminated with toxins tend to give birth to smaller babies who may have difficulty recognising visual patterns seen by other babies, according to Professor Mike Dickman of Hong Kong University. These fish may feed on the plants and animals that live in the sediment and are at the bottom of the food chain, he said. A study he did in the Great Lakes confirmed the occurrence of deformities in small plants and animals, and for the Hong Kong study he is particularly interested in waters polluted by dyes because the dyes contain deformity-causing chemicals. ''If these substances are capable of causing deformities in small animals, might they not also affect humans? I don't know the answer, but I suspect our metabolisms are similar to theirs,'' he said. ''They may be like the old canary in the mine which is saying, look at what's happening to me - you're next.'' Professor Dickman begins the study this month and expects preliminary results by late summer. He will take sediment samples at 28 places, based on where the Environmental Protection Department (EPD) also takes samples. The toxicity results of his study will be compared with the chemical results of the EPD's samples to see what link there is between pollution and deaths or deformities in marine life. This kind of study has not been done in Hong Kong before. Some fish farms operate in Tolo Harbour, but Professor Dickman said he would not be investigating these at this point. The project is intended to run over three years at a cost of $1 million, but only $62,000 has been secured and more funds are being sought.