Hexachlorobenzene exposure and the proportion of male births in Turkey 1935-1990

Hexachlorobenzene (C(6)Cl(6), HCB) is a chemical that has been associated with significant immediate and long term adverse health effects in humans. It has been associated with both porphyria cutanea tarda and spontaneous abortions among survivors of widespread exposure in the 1950s in southeastern Turkey. HCB binds to the Ah receptor, albeit with lower affinity than dioxin. Dioxin exposure has been reported to lower human secondary sex ratio, putatively through a male mediated effect. We therefore wished to evaluate the impact of the HCB environmental event on the sex ratio of the progeny of the survivors. We undertook an assessment of 1) the effects of HCB exposure on the proportion of male births of individual subjects who had survived, 2) variables that significantly predicted the proportion of males among these individuals, and 3) the trend of the population sex ratio born in Turkey from 1935 to 1990. Women known to have been exposed to HCB in the 1950s did not have offspring with a significantly different sex ratio when compared to control populations. However, subjects reporting exposure at the peak of the episode (1955-57) had a significantly lower lifetime proportion of males than those exposed at a later date. The lifetime reported spontaneous abortion rate of these women also significantly predicted the percent males per subject. The available national data demonstrated a significant reduction in the calculated proportion of males from 1935 to 1970 that stabilized from 1970 to 1990. These data indicate that HCB exposure that was sufficient to induce clinical porphyria cutanea tarda may also have reduced the proportion of males in subjects over their reproductive life-span. The HCB episode does not explain the pattern of the national trend from a population perspective.