Open chemical combustions resulting in a local increased incidence of orofacial clefts.

HYPOTHESIS: The open chemical combustions in Zeeburg, Amsterdam, The Netherlands, during the years 1961 up to and including 1969, resulted in a local increased incidence of orofacial clefts during this period. STUDY: A retrospective observational epidemiological study was performed, comparing the trend of the incidence of non-syndromal orofacial clefts during the sixties, for the Zeeburg maternity with that of the Wilhelmina Gasthuis. Both clinics were situated in Amsterdam, but varying in distance and compass direction from the incineration works. Thereafter, the addresses of the mothers giving birth to infants with orofacial clefts were plotted on a map of Amsterdam.
RESULTS: Of the 8803 children born in the Zeeburg clinic during this period, 21 had a non-syndromal orofacial cleft, producing an average incidence of 2.4 per 1000 births. For the years 1963 through 1965 the incidence rose dramatically to peak at 7.1 per 1000, before plateauing at an average incidence of 1.68 per 1000 births, still 155% higher than in the Wilhelmina clinic (average incidence of 0.66 per 1000 during the years 1966 through 1969). During the 10 year period the Wilhelmina clinic exhibited no such rise. The incidence of non-syndromal orofacial clefts at the Wilhelmina clinic at no time exceeded 2.3 per 1000 births during the 10 year period. The addresses of the mothers of the Zeeburg clefts were grouped primarily to the northwest (and a smaller group to the west) of the incineration works.
CONCLUSION: A relation between the open incineration of the chemicals and a local increased incidence of orofacial clefts seems very likely.