Exposure to lead or mercury takes place through the inhalation, the ingestion of contaminated water or food or through the placenta or the maternal breastfeeding in children.
Lead is a natural metal that can be found in several zones of the environment, although most of it comes from the activities of the mankind, like the production of batteries and the ammunition among others. Due to the preoccupation for the effects of this metal on the human health, its presence has been reduced in gasoline, paint and ceramics.
Little children are exposed to this metal through the ingestion of paints that contain lead, for example, licking painted toys. Children are more vulnerable to the poisoning for lead than are the adults, since a child ingesting great amounts of lead can develop anaemia, stomachache, muscular weakness and alterations in the nervous system. The foetuses are exposed through their mothers and the potential effects on the infantile health include prematurity, delay in growth, alterations in mental abilities, difficulties in the learning and alterations in the motor development.
Mercury is a metal that, combined with other elements like sulphide or oxygen, forms inorganic mercury or the mercury salts, that are used as dusts or crystals in antiseptic or cosmetic creams. The main source of mercury is the fossil fuel use, fundamentally the coal that contains plans of this metal. When being burned, this compound enters the environment. In anaerobic means (when there is no oxygen) the bacteria transform it into methylmercury. This form is the one that bioaccumulates with more facility in organisms and people. Besides, it is a metal that is used in medical thermometers (and some other medical instruments), in dental treatments and fluorescent lights and batteries.
Just as it happened with the lead, the children are more sensible to the effects of mercury than the adults. Within these effects, we must point out damages in the nervous system, mental delay, incoordination, blindness and difficulties in the speech.