title: Toxicity of 17alpha-ethynylestradiol and norethindrone, constituents of an oral contraceptive pill to the swimming and reproduction of cladoceran Daphnia magna, with special reference to their synergetic effect.
abstract: Toxicity of 17alpha-ethynylestradiol (EE2) and norethindrone (NOR), constituents of low dosage oral contraceptives, was assessed for the freshwater cladoceran Daphnia magna. Acute toxicity tests showed that 5 ppm of EE2, the highest concentration in this study, never inhibited swimming, whereas NOR inhibited swimming at >3 ppm: 48 h EC(50) for NOR was 6.41 ppm. Chronic toxicity tests were carried out for 25 days by measuring the number of offspring, moltings and sex ratios of neonates at 20, 100 and 500 ppb. EE2>100 ppb significantly decreased the number of offspring to 75% of the control; however, no effect was observed in molting and sex ratios at <500 ppb. NOR did not affect reproduction and sex ratios at <500 ppb. Mixture of EE2 (5.88 ppb) and NOR (94.12 ppb) also significantly decreased the number of offspring to 57% of the control. This result indicates the importance of examining synergetic effects of chemicals in the context of natural environments which face exposure to myriad chemicals.
authors.affiliation: Graduate School of Bioresource Sciences, Nihon University, Kameino 1866, Fujisawa, 252-8510, Kanagawa, Japan. utogo@mac.com
authors.forename: Takashi
authors.initials: T
authors.lastname: Goto
authors.forename: Juro
authors.initials: J
authors.lastname: Hiromi
mesh_terms: D000818:Animals; D003276:Contraceptives, Oral / Q000737:chemistry; D003621:Daphnia / Q000502:physiology*; D045166:Estradiol Congeners / Q000633:toxicity*; D004997:Ethinyl Estradiol / Q000633:toxicity*; D005260:Female; D005298:Fertility / Q000187:drug effects; D007928:Lethal Dose 50; D008297:Male; D018978:Molting / Q000187:drug effects; D009640:Norethindrone / Q000633:toxicity*; D045167:Progesterone Congeners / Q000633:toxicity*; D012744:Sex Ratio; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D003276:Contraceptives, Oral; D045166:Estradiol Congeners; D045167:Progesterone Congeners; D014874:Water Pollutants, Chemical; D004997:Ethinyl Estradiol; D009640:Norethindrone