The effects of 1, 2, 3, 4, 10, 10-hexachloro-1, 4, 4a, 5, 8, 8a-hexahydroxy endo, exo-5, 8-dimethionaphthalene (aldrin) and sodium ethylenebisdithiocarbomate (nabam) on the chick.

Fertile White Leghorn chicken eggs were injected on the tenth day of incubation with either 0, 10, 20, 30, 40 or 50 p.p.m. Aldrin or 0, 5, 10 or 15 p.p.m. Nabam and allowed to hatch. Aldrin neither did induce any deformities nor had any effect on hatchability, thyroid weight and histology. However, within three days after hatching, there was greater mortality in chicks treated with higher concentrations of the pesticide. Aldrin at higher concentrations significantly reduced 125I uptake by the thyroids. This was evident in the iodine fractions after chromatographic separation of the thyroid extracts. Nabam not only reduced hatchability but also induced deformities in the higher concentration groups. The thyroids showed an increase of resorption vacuoles in the colloid. Even though the thyroid weights increased in all experimental groups, a significant increase in 125I uptake was seen only in the 15 p.p.m. injected animals. This group also showed a reduction in radioactivity of thyroxine fraction but an increase of 125I in tyrosines. The significance of these results are discussed.