Exposure to carbon black: a cancer risk?

Abstract

Lung cancer is one of the most serious health problems in the industrial nations and is therefore of great public and scientific interest. Although inhalative cigarette smoking is without doubt the main cause for the increasing frequency of lung cancer, during recent years there has been more and more public interest in other substances in the environment or at the work place that are assumed to be potentially carcinogenic especially due to experiences with fibrous particles such as asbestos and their effects. Enhanced attention is also directed to inert or nuisance dusts such as carbon black. Evaluation of the possibly increased risk for humans should first be based on exact epidemiology data. In the absence of those data--as in the case of carbon black--experimental data in animals serve as the point of orientation, especially results gained in rats in long-term inhalation studies. Pathologic anatomy investigations of human lungs under similar exposure conditions, however, render results quite different from those obtained in rats and, thus, preclude ready interpretation of animal results to human risk assessment. This is particularly true for the development of lung tumors in rats under overload conditions as well as for certain tumor types not observed in human lung tissues. It is therefore quite understandable that many researchers propose to interpret the changes observed in rat lung tissues after inhalation of carbon black as rat-specific reaction mechanisms that cannot be applied to human tissues, which in the past have led to the wrong conclusions regarding human risk assessment due, among other factors, to incorrect experimental design and inaccurate nomenclature of tumorous lesions in rats.

Particulate Exposure During the Persian Gulf War

“…Carbon black is produced by a number of commercial processes, one of which is thermal decomposition (combustion) of aromatic oil and coal tar distillates to produce carbon particles in the 0.01 nm-0.5 urn range, with thermal decomposition producing generally larger soot particles in the 0.12-0.5 urn range. 77 USAEHA found that Gulf War soot was a mixture of small carbon chain agglomerates of 0.1 urn and larger carbon chains composed of spherical particles 0.25 urn or greater. 78 Since Gulf War soot was produced by petroleum thermal decomposition, carbon chain agglomeration with spherical carbon particles similar to commercial carbon blacks would be expected.…”

Carbon black should not be classified as a human carcinogen based on rodent bioassay data

“…These effects are attributed to a non-specific irritant effect of heavy dust exposure a BIBRA (1990), Brockmann et al (1998), Gardiner et al (1993), Gardiner (1995), IARC (1996), Kupper et al (1996), Robertson (1996), Robertson et al (1988), Szozda (1994). (Gardiner et al, 1993).…”

“…Effects of dust exposure were reported to include increased alterations in the upper respiratory tract, complaints of bronchitis, slight, reversible lung function changes with levels of exposure above the occupational exposure limits and slight pneumoconiotic changes depending on exposure'' (Brockmann et al, 1998).…”

“…In another recent review article (Brockmann et al, 1998), morbidity was compared between Eastern European and Western countries. In Eastern Europe more serious morbidity changes are reported and include a wide range of symptoms including bronchitis, mild pneumoconiosis, slight lung function changes, and advanced pulmonary fibrosis.…”

Soot Measurements in Steady and Pulsed Ethylene/Air Diffusion Flames Using Laser-Induced Incandescence

“…For example, the amount of exposure for a person living in San Francisco, and traveling by car on 280 to work at Stanford University was expressed as DACEE (the Daily Cigarette Exposure Equivalent) being equal to 3.6 while DACEE being 1.0 represents a standard cigarette smoker (Siegmann and Siegmann 1997). In October 1995, International Agency for Research on Cancer assessed the results on a scientific basis with regard to a possible carcinogenic effect using carbon black (Brockmann et al 1998). …”