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1) There is no evidence of any fibrotic lung disease (interstitial fibrosis) from evaluations of chest
X-rays.

2) There is no evidence of an elevated incidence of lung disease among RCF manufacturing
employees.

3) In early studies, an apparent statistical “trend” was observed, in the exposed population,
between RCF exposure duration and some measures of lung function. The observations were
clinically insignificant. If these observations were made on an individual employee, the results
would be interpreted as being within the normal (predicted) respiratory range. A more recent
longitudinal study of employees with 5 or more pulmonary function tests found that there was no
effect on lung function associated with RCF production experience. Initial data (circa 1987)
seemed to indicate an interactive effect between smoking and RCF exposure; more recent data,
however, found no interactive effect. Nevertheless, to promote good health, RCF employees are
still actively encouraged not to smoke.

4) Pleural plaques (thickening along the chest wall) have been observed in a small number of
RCF employees. Some studies appear to show a relationship between the occurence of pleural
plaques on chest radiographs and the following variables: (a) years since RCF production hire
date; (b) duration of RCF production employment; and (c) cumulative RCF exposure. The best
evidence to date indicates that pleural plaques are a marker of exposure only. Pleural plaques
are not associated with pulmonary impairment. The pathogenesis of pleural plaques remains
incompletely understood; however, the mechanism appears to be an inflammatory response
caused by inhaled fibers.

TOXICOLOGY

A number of toxicological studies designed to identify any potential health effects from RCF
exposure have been completed. In one study, conducted by the Research and Consulting
Company, (Geneva, Switzerland), rats and hamsters were exposed to 30 mg/m³ (about 200
fibers/cc) of specially-prepared RCF for 6 hours/day, 5 days/week, for up to 24 months. In rats, a
statistically significant increase in lung tumors was observed; two mesotheliomas (cancer of the
pleural lining between the chest wall and lung) were also identified. Hamsters did not develop
lung tumors; however, interstitial fibrosis and mesothelioma was found. Some, in the scientific
community, have concluded that the “maximum tolerated dose” was exceeded and that significant
particle contamination was a confounding issue; therefore, these study findings may not
represent an accurate assessment of the potential for RCF to produce adverse health effects.

In a related multi-dose study with a similar protocol, other rats were exposed to doses of 16
mg/m³, 9 mg/m³, 3 mg/m³ which corresponds to about 115, 75, and 25 fibers per cubic centimeter
respectively. This study found no statistically significant increase in lung cancer. Some cases of
pleural and parenchymal fibrosis were seen in the 16 mg/m³ dose group. Some cases of mild
fibrosis and one mesothelioma were observed in the 9 mg/m³ group. No acute respiratory effects
were seen in the rats in the 3 mg/m³ exposure group, which suggests that there may be a
dose/response threshold, below which irreversible respiratory impacts do not occur.

Other toxicological studies have been conducted which utilized non-physiological exposure
methods such as intrapleural, intraperitoneal and intratracheal implantation or injection. Some of
these studies have found that RCF is a potential carcinogen. Some experts, however, suggest
that these tests have limited relevance because they bypass many of the biological mechanisms
that prevent fiber deposition or facilitate fiber clearance.

To obtain more epidemiology or toxicology information, please call the toll free telephone number
for the Unifrax Corporation Product Stewardship Program found in Section 16 - Other Information.

FurnacePros LA-309, Owner'S Manual

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