Introduction Toxic heavy metals and routes of exposure Features of toxicity
Heavy metals are chemical elements that are commonly found in our environment. Without realising it all people are exposed to heavy metals on a daily basis. However, the quantities that we inhale, ingest or come into contact with the skin are so small that they are usually harmless. In fact, small amounts of some heavy metals in our diet are essential to good health. These are referred to as trace elements and include iron, copper, manganese, zinc, plus others, which are commonly found naturally in fruits and vegetables.
Toxic heavy metals are heavy metals that become poisonous to the body when they are not metabolised or excreted and so accumulate in organs and tissues. They enter the human body through food, water, air, or absorption through the skin. Routes of exposure are described below.
Industrial exposure is the usual route of exposure for adults. Several heavy metals are used or produced as a by-product in many agricultural, manufacturing and pharmaceutical processes.
Lead
Cadmium
Iron
The most common route of exposure to heavy metals in children is through accidental ingestion. Toxic levels of heavy metals can develop through the regular hand-to-mouth activity of small children who play in contaminated soils or eat/chew on objects that are not food, such as bark chips, dirt or painted objects.
Signs and symptoms of toxicity depend on the heavy metal involved and whether an exposure causes acute toxicity or chronic and subtle effects.
Signs and symptoms of acute toxicity
Signs and symptoms of chronic exposure
The heavy metals that cause the most significant skin changes and are discussed in more detail include arsenic, silver, gold and mercury.
