Toxicity of rubber chemicals towards three-day chicken embryos.

Three-day chicken embryos were exposed to 80 different rubber chemicals dissolved in either acetone or water. The following classes of chemicals were studied: thiurams, dithiocarbamates, thioureas, benzothiazoles, benzenesulfohydrazide, dithiodimorpholine, amines, acrylates, guanidines, resorcinol, phthalates, adipates, phosphates, oils, peroxides, heavy metal salts, and sodium nitrite. Dose-response curves and median lethal doses (LD50) or median effective doses (ED50) were calculated for mortality in 2 d after the treatment, for total mortality in 11 d after the treatment, and for the total effect, including deaths and malformations 11 d after the treatment, when the test was finished. Sixteen of the chemicals had no effect on the embryos when injected into the air chamber. Incomplete and irregular dose-response curves for the total effect were obtained with 13 of the chemicals. For them, the ED50 could be calculated. Among the remaining 51 chemicals, the most potent were the dithiocarbamates and cadmium and copper acetates, with the total effect ED50 from 2.4 to 160 nmol/egg. Other chemicals that had an ED50 smaller than 100 nmol/egg were thiurams, cyclohexylthiophthalimide, acrolein, and dithiodimorpholine. The majority of the chemicals had an ED50 between 100 nmol/egg and 10 mumol/egg. The least potent were sodium nitrite and methylmethacrylate with an ED50 of 22 mumol/egg. All the 64 embryotoxic chemicals caused malformations with only one exception (dibutylthiourea). The maximum observed frequencies of malformed embryos varied from 3 to 100% of the treated embryos.