Can Cytotoxic Effects Induced by Industrial Chemicals be Time-dependent?

Short-term and delayed cytotoxic effects of selected water-soluble and water-insoluble industrial chemicals (dimethyl sulphoxide, ethyl alcohol, methyl alcohol, ammonium nitrate, benzalkonium chloride, butoxyethanol and propylene glycol) were tested on confluent 3T3-L1 mouse fibroblasts by using the neutral red uptake (NRU) assay and the MTT assay. The NRU and MTT assays were performed after exposure to a chemical for 10 minutes and 3 hours and then again 7 days later. The results indicate that the system of testing used permits the assessment of both early and delayed cytotoxic effects of different classes of chemicals. Our experiments revealed that three out of the seven substances tested (butoxyethanol, dimethyl sulphoxide and propylene glycol) exhibited similar cytotoxic effects when assessed after exposure for 10 minutes and 7 days later. The results for ammonium nitrate, ethyl alcohol and methyl alcohol, tested after exposure for 10 minutes and 7 days later, did not significantly differ from each other. However, we noted that the cytotoxic effects observed 7 days after exposure were more pronounced than those found for the same concentration, after exposure for 3 hours. One chemical tested (benzalkonium chloride) had almost no cytotoxic effect after exposure for 10 minutes and 3 hours, but showed a strong cytotoxic effect 7 days after exposure. Our study indicated that the cytotoxic effect might be time-dependent in some chemicals, thus inducing a delayed effect in vitro. In our opinion, it is advisable to assess the cytotoxicity of a chemical after exposure for 3 hours (for immediate effects) and again 7 days later (for delayed effects).

Occupational allergy to aldehydes in health care workers. Clinical observations. Experiments.

The incidence of allergy to aldehydes (formaldehyde, glutaraldehyde, glyoxal) was examined in 280 health care workers suffering from skin lesions. Allergy was diagnosed in 64 (22.8%) patients. The majority of them (85.9%) were sensitive only to 1 aldehyde. Formaldehyde caused allergy slightly more frequently (13.9%) than glutaraldehyde (12.4%). Only 5 (1.9%) patients were sensitive to glyoxal. The irritant effect of aldehydes to the rabbit eye and skin was tested by the Draize and OECD methods. Formaldehyde and glutaraldehyde showed stronger irritant effect than glyoxal. The sensitizing activity of aldehydes was also confirmed in guinea pigs (using the Maximization Test and the OECD methods). Formaldehyde showed the strongest and most persistent reactions. Significantly higher eosinophil and basophil counts were found in the blood samples of the sensitized guinea pigs. Cytotoxicity of glutaraldehyde and glyoxal was tested on mouse 3T3-L1 fibroblasts by the Neutral Red Uptake and MTT Reduction Assay. It was shown that both aldehydes were cytotoxic, and that the cytotoxic effect of glutaraldehyde was stronger than that of glyoxal.