The trace element selenium is probably not a problem in agricultural drain water in the western San Joaquin Valley, but the elements boron and molybdenum need more study, a report said. Selenium dissolved in farm drainage water funneled to the Kesterson National Wildlife Refuge was blamed for massive bird deformities in the early 1980s after it entered the food chain. Health advisories were later issued urging limitations on consumption of fish and birds in the Kesterson area and around similar farm waste water evaporation ponds in the western valley. But the report, prepared for the federal-state San Joaquin Valley Drainage Program by the Health Officers Assn. of California, says selenium is probably not a problem in crops or livestock. Selenium can be toxic and capable of causing animal mutations at slightly higher levels and can disrupt reproduction.