A considerable reduction in the blood levels of stable organic pollutants (SOP) has been noted in the mothers of native ethnicities of costal Chukotka during a 5-year period, which may be accounted for by certain purification of food chains, altered diet with emphasis on delivered products, and long-term breastfeeding. The elevated level of SOP in children from birth to age 5 years is explained by long-term breastfeeding and the early consumption of local foods. The content of heavy metals (mercury and lead) in both maternal and children's blood has unchanged for 5 years. The children's infection morbidity has been quite high; at the same time no associations of the children's blood levels of toxic substances with the incidence of infectious diseases have been found. However, two children maximally exposed to SOP and metals have been observed to be rarely susceptible to diseases.