Posted By Adrian Watson
Lead poisoning is one of the commonest of occupational diseases. The presence of lead-bearing materials or lead compounds in an industrial plant does not necessarily result in exposure on the part of the worker. The lead must be in such form, and so distributed, as to gain entrance into the body or tissues of the worker in measurable quantity, otherwise no exposure can be said to exist. Some lead compounds are carcinogens of the lungs and kidneys.
The modes of entry into body are by inhalation of the dust, fumes, mists or vapours; by ingestion of lead compounds trapped in the upper respiratory tract or introduced into the mouth on food, tobacco, fingers, or other objects; and through the skin; this route is of special importance in the case of organic compounds of lead, such as lead tetraethyl. In the case of the inorganic forms of lead, this route is of no practical importance.
When lead is ingested, much of it passes through the body unabsorbed, and is eliminated in the faeces. The greater portion of the lead that is absorbed is caught by the liver and excreted, in part, in the bile. For this reason, larger amounts of lead are necessary to cause toxic effects by this route, and a longer period of exposure is usually necessary to produce symptoms. On the other hand, upon inhalation, absorption takes place easily from the respiratory tract and symptoms tend to develop more quickly. For industry, inhalation is much more important than is ingestion.
Metallic Lead causes human systemic effects by ingestion and inhalation. It produces loss of appetite, anaemia, malaise, insomnia, headache, irritability, muscle and joint pains, tremors, flaccid paralysis without anaesthesia, hallucinations and distorted perceptions, muscle weakness, gastritis and liver changes. The major organ systems affected are the nervous system, blood system, and kidneys.Very heavy intoxication can sometimes be detected by formation of a dark line on the gum margins, the so-called “lead line.”
The toxicity of the various lead compounds appears to depend upon several factors, such as the solubility of the compound in the body fluids; the fineness of the particles of the compound (solubility is greater in proportion to the fineness of the particles); and conditions under which the compound is being used.
Of the various lead compounds, the carbonate, the monoxide, and the sulphate are considered to be more toxic than metallic lead or other lead compounds. Lead arsenate is very toxic due to the presence of the arsenic radical. Organolead compounds are rapidly absorbed by the respiratory and gastrointestinal systems and through the skin. Tetraethyl lead is converted in the body to triethyl lead which is a more severe neurotoxin than inorganic lead.