[Teratogenic effect of the pesticide preparation metathion]

A total of 600 chick embryos were used to test the teratogenic action of the phosphorous organic pesticide metathion in a 89.3 per cent substance. The embryonated eggs used had equal weight (62 +/- 1 g), and originated from the pure genetic Plymouth line 33. On the 2nd day of incubation sterile injection was made in the yolk sac as follows: i group--4.9 mg/kg metathion solved in propyleneglycol; II group--2.45 mg/kg metathion in propyleneglycol; III group--with propyleneglycol alone; IV group--treatment via sterile prick only; and V group--controls. As many as 40 embryos per group were investigated on the 14th, 18th, and 21st day, being brightened after the alizarin method. It was found that metathion-treated embryos (Group I and II) had according to the dose used, strongly manifested weight loss as early as the 14th day of incubation as against the other two groups. Both propyleneglycol and pricking did not produce unfavourable effects on the rate of growth. In more than 20 per cent of the metathion treated embryos there were total or partial edematization of the body and lagging behind in feathering. The teratogenic effect was most strongly manifested with regard to the bone system. Most characteristic proved the malformations in the skull bones, substantiating the so called 'parrot bill' deformity. With the legs most characteristic were their shortening, thickening and caudolateral flexing of the tibia which assumed a G-shaped form. It is believed that the teratogenic effect of metathion is due to its anti-vitamin action (abiotin effect). At 2.45 mg/kg it causes 80 per cent malformations in all cases, and at 4.9 mg/kg--95 per cent. The abnormalities are predominantly of the micromelia type.