The Occupational Safety and Health Act of 1970 emphasizes the need for standards to protect the health and safety of workers exposed to an ever-increasing number of potential hazards in their workplace. Pursuant to the fulfillment of this need, the National Institute for Occupational Safety and Health (NIOSH) has developed a strategy of disseminating information about adverse effects of widely used chemical or physical agents intended to assist employers in providing protection for employees from exposure to substances considered to possess carcinogenic, mutagenic, or teratogenic potential. This strategy includes the development of Special Occupational Hazard Reviews which serve to support and complement the other major standards development or hazards documentation activities of the Institute. The purpose of Special Occupational Hazard Reviews is to analyze and document, from a health standpoint, the problems associated with a given industrial chemical, process, or physical agent, and to recommend the implementation of engineering controls and work practices to ameliorate these problems. While Special Occupational Hazard Reviews are not intended to supplant the more comprehensive NIOSH Criteria Documents, nor the brief NIOSH Current Intelligence Bulletins, they are nevertheless prepared in such a way as to assist in the formulation of regulations. Special Occupational Hazard Reviews are disseminated to the occupational health community at large, e.g., trade associations, industries, unions, and members of the scfy^ntific community. r\ ' Institute lillav, distant Surgeon#
(Clark, 1977b
(Clark, , 1977c
The observed incidences of hepatocellular carcinoma in mice were dose-related and highly significant (p < .01) at both dose levels in male mice and at the higher level in female mice (Table 6) . The increase observed in low dose female mice was found to be significant at a p-value of 0.09.
A week and six more by the end of the 78th week of exposure. By contrast, in the low-dose group, the first liver tumor was not observed until after 81 weeks in male mice. Thus, in male mice.  -12 weeks at 1000/2000 mg/kg/day; 66 weeks at 1200/2400 mg/kg/day.

# Sice (F)
-12 weeks at 700/1400 mg/kg/day; 66 weeks at 900/1800 mg/kg/day. fiats (!i/F) -7 weeks at 650/1300 mg/kg/day; 9 weeks at 750/1500 mg/kg/day; 62 weeks at 500/1000 my/kg/day.   Figure 3
DOSE L E V E L S (M G /K G )
Relationship of hepatocellular carcinoma incidence with dose levels for trichloroethylene (TCE)# tetrachloroethylene (PCE) g chloroform (ChCl-^) t and carbon tetrachloride (CCl^ . The mechanism, i.e., induction or promotion, is not resolved.
In some cases, parts were not given adequate time to drain prior to their removal from the degreasing unit, allowing for increased concentrations of solvent vapor in the operators' breathing zones. Disturbances of the vapor layer and solvent "dragout" also occurred from removing or introducing parts too quickly.
Freeboard exhaust ducts sometimes were badly in need of cleaning and were partially clogged, thereby interfering with proper exhaust.
In some cases, heat exchange coils on the compressor of freeboard chillers needed cleaning for the unit to operate effectively in condensing the vapor and containing it within the degeasing unit.
In most cases, degreaser covers were not in use.
In some cases they had never been installed, while for others they had been removed or intentionally not used even while the unit was idling.
Employees