PRINCIPLES OF TOXICOLOGY

Industrially Related or Occupational Asthma
Many individuals develop asthma following workplace exposure, and some asthmatics suffer additional
provocation following the inhalation of certain industrial toxins. The inhalation of wood dusts,
for instance, has been implicated in both situations. Some grocery workers have developed an asthmatic
condition following the wrapping of meats with plastic film. Apparently, heating the plastic to seal it
releases toluene diisocyanate, which is then inhaled. Subsequent exposure to even very low levels of
the plastic, or its component, may result in a severe reoccurrence of symptoms.
It has been shown that the bronchiolar muscles of asthmatics will undergo constriction at a lower
concentration of inhaled industrial chemicals than will those of nonasthmatics. Not surprisingly, these
individuals often find themselves reacting in situations in which their co-workers do not respond. A
further complication for these workers is that exercise tends to exacerbate the asthma symptoms.
Physical exertion, obviously required in many industrial situations, along with the simultaneously
chemical exposure can lead to severe complications for the affected worker.
Lung Cancer
Until the twentieth century, lung cancer was relatively rare. The rapid promotion of lung cancer to the
number one cancer killer is directly related to the inhalation of tobacco smoke (probably 80–90 percent
of all lung cancers) and industrial/atmospheric chemicals. The relationship between tobacco smoke
inhalation and lung cancer was discussed previously. Many industrial chemicals have also been linked
to lung cancer in workers and laboratory animal studies.
The dusts and fumes of many metals have been demonstrated to be carcinogenic in lung tissue.
Epidemiologic studies conducted on worker populations in smelting operations have long shown
definitive relationships between metal inhalation and lung cancer. Industrial metal carcinogens include
nickel, arsenic, cadmium, chromium, and beryllium. Workers in mining operations, including metal
recovery from ores, are at risk for developing lung cancers because of exposure to certain metals such
as chromium and uranium. The inhalation of benzo(a)pyrene and other polycyclic aromatic hydrocarbons,
from coke oven emissions, has also been linked to the development of lung cancer.
Radioactive materials have long been recognized as inducers of lung cancer. Uranium miners have
an elevated incidence of lung cancers, as did the victims of the atomic bomb explosions at Hiroshima
and Nagasaki. Recently, the potential for inhalation of radon gas has become a concern, due to the
large population with the possibility for long-term exposure. Smoking has been shown to exacerbate
the incidence of lung cancer when in conjunction with exposure to radioactive materials.
An important feature regarding the development of lung cancer in humans is the generally long
latent period. Normally it takes 20–40 years following the inhalation of most toxins before lung tumors
appear. For this reason, it is often difficult to establish the definitive etiology of the lung cancer. Cancer
of the upper respiratory tract does occur and is associated with some professions, such as chromate
and nickel industry workers. By far, though, the majority of respiratory system cancers occur in the
bronchioles and the lung tissues.
9.3 SUMMARY
The lungs provide a unique pathway for industrial toxins and tobacco smoke to enter the body, since
the interface between the alveolar air and the pulmonary blood can facilitate the diffusion of both
life-giving air and life-threatening toxins. The beautiful design of the respiratory system provides a
number of highly efficient methods of protection from commonly encountered potential toxins,
including
• Humidification and temperature control
• The mucociliary escalator
9.3 SUMMARY 185