The lung is the major route through which toxic substances in the workplace enter the body. It is also the first organ to be affected by dusts, metal fumes, solvent vapours and corrosive gases. When dust particles of a certain size of some substances are inhaled the lungs are unable to remove them. They become embedded in the lung causing a condition called pneumoconiosis. Other substances, such as formaldehyde, sulphur dioxide, nitrogen oxides and acid mists may cause irritation and reduce the breathing capacity.
Some metals affect the nervous system, especially heavy metals such as lead, mercury and manganese.
The blood circulation is a target for the adverse effects of solvents. Blood cells are mainly produced in the bone marrow. To study mutation, lymphocytes are cultured in the laboratory to observe specific types of cellular changes. Lead, in the form of the metal or its compounds, is another classic example of a chemical that may cause blood problems. Lead in the blood may inhibit certain enzyme activities involved in the production of hemoglobin in red blood cells.