The paper shows guidelines used to develop a procedure for detecting heavy metals in biological fluids (urine, bile, gastric juice, blood, hair, placenta, meconium, breast milk) by atomic absorption spectrophotometry at the level of 10(-1)-10(-3) microg/ml(-1) with the maximum analysis error of 17.9%. It also proposes guidelines for determining (calculating) the regional background levels of metals in the biological media of children (in case of the Perm Region). The guidelines have been used to compare the ecological situation in large industrial towns of the Perm Region in compliance with the standard levels of metals in the biological media. The results of studies of risk groups, such as lying women and neonatal infants, show a number of relationships and regularities that lie in diminishing the barrier function of the placenta in the mother-newborn system in a poor environmental area.