Dynamics of steroid estrogen daily concentrations in hospital effluent and connected waste water treatment plant

Abstract

Hospital effluent and connected waste water treatment plant (WWTP) influent and effluent were sampled daily to determine the levels and inter-day variations of three naturally occurring steroid estrogens: estrone, 17β-estradiol, estriol, and synthetic 17α-ethinylestradiol. After solid phase extraction, interferences were removed with a silica gel clean-up step and the samples analysed using gas chromatography with mass selective detection (GC-MSD). The determined inter-day concentrations in hospital effluent were between 8.6 to 31.3 ng L(-1) for estrone, <LOD (limit of detection) to 4.2 ng L(-1) for 17β-estradiol and 6.4 to 385.5 ng L(-1) for estriol. In the WWTP influent concentrations were 18.9 to 49.7 ng L(-1) for estrone, 2.4 to 12.7 ng L(-1), for 17β-estradiol and <LOQ (limit of quantitation) to 63.9 ng L(-1) for estriol. Reduced levels were found in the WWTP effluent: <7.1 ng L(-1) for estrone, <LOQ for 17β-estradiol and <5.2 ng L(-1) for estriol. 17α-ethinylestradiol was detected in only one influent sample. Calculated estradiol equivalents (EEQ) were 33.4, 22.4, 1.7 ng (EEQ) L(-1) in the hospital effluent, WWTP influent and WWTP effluent, respectively. Interestingly, the estrone: 17β-estradiol:estriol ratio in the hospital effluent (1:0.1:9.4) is comparable to that found in the urine of pregnant women (1:0.3:20) indicating the most likely source of steroid estrogens. In WWTP influent the ratio was similar to that found in the non-pregnant population. Our result recognise estriol as being one of the most important steroid estrogens, accounting for up to 92% of the total EEQ present in hospital samples and 37% and 46% in WWTP influent and effluent samples, respectively. The study reveals how concentrations of steroid estrogens vary on a daily basis and concludes that careful sampling strategies must be adopted when making a risk assessment. In addition, the low potency steroid estrogens that contribute towards overall estrogenicity of the sample, e.g. estriol, should be incorporated into environmental monitoring programs.