JAMA : the journal of the American Medical Association
-
Tear gas has gained widespread acceptance as a means of controlling civilian crowds and subduing barricaded criminals. The most widely used forms of tear gas have been o-chlorobenzylidenemalononitrile and omega-chloroacetophenone. Proponents of their use claim that, if used correctly, the noxious effects of exposure are transient and of no long-term consequences. ⋯ Sadly, the nature of its use renders analytic epidemiologic investigation of exposed persons difficult. In 1969, eighty countries voted to include tear gas agents among chemical weapons banned under the Geneva Protocol. There is an ongoing need for investigation into the full toxicological potential of tear gas chemicals and renewed debate on whether their use can be condoned under any circumstances.
-
Multicenter Study Comparative Study Clinical Trial
Facts and artifacts about anemia and preterm delivery.
The effect of anemia (hematocrit less than or equal to 0.34) on subsequent preterm birth was prospectively studied in 35,423 pregnancies. The incidence of preterm birth among women with and without anemia at each week during the third trimester was compared. Early in the third trimester, there was a weak association between anemia and preterm delivery. ⋯ Compared with hematocrits at 40 weeks' gestation, the odds ratios for anemia reached a maximum at 28 weeks and fell sharply as term approached. When the hematocrits of women in term labor were compared with those of women in preterm labor, a spurious dose-response effect for anemia was created. We conclude that anemia is not a strong factor in the pathogenesis of preterm birth and that comparison of hematocrits from women who are in preterm and term labor produces biased results.