Biochemical studies of the tracheobronchial epithelium

Potential carcinogenicity of foundry fumes: a comparative in vivo-in vitro study

Epidemiological studies of workers exposed to fumes in the iron and steel foundry industry have consistently demonstrated an increased relative risk of lung cancer of approximately 1.4. Foundry fume is a complex mixture of gases and fine particles generated during the casting process when molten metal is poured into sand moulds bound together with organic binders. The chemical composition of fume varies according to foundry process and, specifically, binder composition. Previous in vitro studies have demonstrated that some fumes have mutagenic activity and that this varies with fume type. The current study has examined the potential carcinogenicity of three fumes in a 2-yr in vivo rodent bioassay using an intrabronchial pellet implantation technique. The toxicity and genotoxicity of the fumes were tested concurrently in a number of in vitro assays including those identifying mutagenicity, unscheduled DNA synthesis, free radical DNA damage and micronucleus induction. The rodent bioassay failed to demonstrate a carcinogenic response, although an increase in preneoplastic lesions was seen in all fume-treated groups relative to controls. When tested in vitro, the fumes were positive in many assays and activity correlated with the polycyclic aromatic hydrocarbon content of the fumes. The employment of a combination of in vitro assays for different genotoxic endpoints, such as those presented in the current study, provides information useful for the overall assessment of carcinogenicity of complex mixtures such as foundry fume.

In vitro cytotoxicity studies of particulate samples in cultures of Hamster Tracheal Epithelial (HTE) cells

Airborne contaminants have been implicated as important contributing factors in the aetiology of tumours of the respiratory tract. A major concern is that the potential carcinogenic activity of the particulate matter may be enhanced by the volatile material, which is adsorbed onto the surface. The cytotoxic potential of complex particulates was evaluated using the Neutral Red uptake method in primary cultures of hamster tracheal epithelial cells. Cytotoxicity of the reference particulates (benzo[a]pyrene adsorbed on to the surface of alumina A, alumina B, ferric oxide and titanium dioxide) was increased when cultures were treated with adsorbed rather than desorbed (plus dimethyl sulfoxide) samples. Foundry fume samples did not show the same effect.