VINYL CHLORIDE

Vinyl chloride (VC) has been used for various applications as
early as the 1920s, but techniques to produce a stable form of
polyvinyl chloride (PVC) did not arise until the 1930s. The
polymerization process required to produce PVC involves
the use of a reactor. After completion of the reaction, the
tank would need cleaning to remove a layer of PVC that had
formed on the walls of the reactor. Currently, high-pressure
jets and solvents are used for this purpose but originally, workers
would climb into the reactors with spatulas or hammers
and chisels. Consequently, they were exposed to high levels of
VC, which was associated with an acute illness manifesting as
headaches, dizziness, visual disturbances, anorexia, abdominal
pains, and dyspnea. 215
Initial concerns regarding potential carcinogenicity were
raised in animal studies. 216 Soon afterward, Creech et al. 217
published a report on the increased incidence of hepatic angiosarcomas
in PVC workers. Based on the results of animal studies
and the demonstration of an increase in hepatic angiosarcoma
in PVC workers, Tabershaw et al. 218 decided to conduct a historical
prospective mortality study of 8384 men who had had
at least 1 year of occupational exposure to VC. They found
13 respiratory cancers compared with 10.28 expected suggesting
a potential role for VC as a pulmonary carcinogen. The
first human study to show a significant increase in lung cancer
was conducted by Waxweiler et al. 219 They performed a retrospective
cohort study on workers exposed to VC at four plants
in the United States and found an excess of respiratory cancers
at plant number four (9 compared with 4.6) and 12 cases of
respiratory malignancies compared with an expected 7.7 at all
plants. Of note, plant 4 contributed more than two thirds of
person-years to the study, which was the reasoning provided by
the authors for conducting a separate analysis at that particular
plant. However, a review of studies of VC and lung cancer
has generated conflicting conclusions regarding the potential
of VC to act as a pulmonary carcinogen. 220–222 There is little
doubt about the role that VC plays in hepatic angiosarcoma,
but its contribution to the development of human lung cancer
is still under debate today. 222
Regardless, the IARC concluded that VC is a human pulmonary
carcinogen as a result of sufficient evidence on the carcinogenicity
in humans. The EPA has mandated that human
exposure be no more than 0.002 mg of VC per liter of water.
The OSHA has set a PEL of 1 ppm of air during an 8-hour
workday during a 40-hour workweek.