And the U.S. Public Health Service recommended that prospective mothers take 4 milligrams of folic acid daily to maintain the optimum level of vitamin B-12. Having this data in advance and helping people deal with it is tremendously important. What caused the vitamin deficiency is another unanswered question. The effects of environmental factors such as air, soil and water pollution are still largely mysteries. So researchers cannot say whether environmental factors cause health problems or trigger and aggravate predisposed conditions.
Autistic clusters confound The mystery of autism exemplifies the frustration of researchers.
Neither its cause nor its extent is known, though the CDC estimates that nearly 300,000 may have the brain disorder, which affects communication and social skills. The Department of Education has reported a quintupling of autism cases among American schoolchildren, but much of that is attributed to greater awareness and improved diagnostic measures. California is one of a few states to investigate autism rates. A cluster of autistic children was discovered in Brick Township, N.J., where four out of every 500 children were diagnosed with the disorder. Federal officials never pinpointed the cause for the high rate, but parents in the area blamed toxins from a landfill.