Ascertaining the Causal Relationship in the Studies of the Effects of Weak Nonionizing Electromagnetic Fields on Embryogenesis of Man

Abstract

In a number of publications positive associations between the exposure to artificially generated nonionizing electromagnetic fields (EMF) and the reproductive risks in women were reported (abortion, birth defects, stillbirths). Yet, in another studies, claimed to be more careful, it has been shown that EMF should not be accounted for as a factor causing measurable increase in the above mentioned reproductive failures. In this context, of crucial importance is the determination whether the observed relationship between EMF and people is not of casual but of causal character.

In epidemiology a simple checklist is often used to establish this type of relationship. However, in the case of weak association the causal relationship may be claimed with a high degree of uncertainty. Taking into account the fact that in situations that are of interest to epidemiology, EMF are one (sometimes seemingly the most important) of a number of factors. Therefore, the above mentioned bioeffects may come into effect only if other factors are also present. It should be also stressed that the intricacy of these relationships increases when the role of such circumstances, as: distribution in time of the expositions, accumulation of dose, different spans of  latency periods, as well as possible stimulatory effects of weak EMF is taken into account.