Spina bifida occulta associated with environmental arsenic exposure in a prehispanic sample from northern Chile

Background: The Camarones River Valley, located in the extreme north of Chile, is characterized by high environmental arsenic levels and an arid desert. It has been inhabited by humans for the past 7,000 years. Evidence exists for chronic arsenic poisoning in both prehispanic and present populations residing in the area. Chronic arsenic exposure causes multi-systemic problems and can induce congenital malformations, in particular neural tube development defects such as spina bifida. Aim: To study the prevalence of spina bifida among prehispanic mummies of the area. Material and Methods: One-hundred and twenty prehistoric adult individuals were analyzed for evidence of spina bifida occulta of the sacrum in skeletal samples from the sites of Camarones 8, Camarones 9, Azapa 140 and Lluta 54, held in repository at the Museo Universidad de Tarapacá de Arica-San Miguel de Azapa. A diagnosis was considered positive when at least S1, S2 or S3 were affected. As controls, mummies of individuals that resided in Lluta and Azapa valley, with a low arsenic exposure, were analyzed. Results: The frequency of spina bifida occulta among samples from the Camarones coast and Lluta and Azapa Valley were 13.5 and 2.4% respectively. Conclusions: Considering these were contemporaneous samples, and are believed to have had no other differences in diet or other factors, the differential exposures to arsenic could have produced the observed differences in spina bifida frequencies.