Occurrence and fate of hormone steroids in the environment

Abstract

Hormone steroids are a group of endocrine disruptors, which are excreted by humans and animals. In this paper, we briefly review the current knowledge on the fate of these steroids in the environment. Natural estrogenic steroids estrone (E1), 17β-estradiol (E2) and estriol (E3) all have a solubility of approximately 13 mg/l, whereas synthetic steroids 17α-ethynylestradiol (EE2) and mestranol (MeEE2) have a solubility of 4.8 and 0.3 mg/l, respectively. These steroids have a moderate binding on sediments and are reported to degrade rapidly in soil and water. Estrogenic steroids have been detected in effluents of sewage treatment plants (STPs) in different countries at concentrations ranging up to 70 ng/l for E1, 64 ng/l for E2, 18 ng/l for E3 and 42 ng/l for EE2. E2 concentrations in river waters from Japan, Germany, Italy and the Netherlands ranged up to 27 ng/l. In addition, E2 concentrations ranging from 6 to 66 ng/l have also been measured in mantled karst aquifers in northwest Arkansas. This contamination of ground water has been associated with poultry litter and cattle manure waste applied on the land. Although hormone steroids have been detected at a number of sources worldwide, currently, there is limited data on the environmental behaviour and fate of these hormone steroids in different environmental media. Consequently, the exposure and risk associated with these chemicals are not adequately understood.

Introduction

Steroid hormones are a group of biologically active compounds that are synthesized from cholesterol and have in common a cyclopentan-o-perhydrophenanthrene ring. Natural steroids are secreted by the adrenal cortex, testis, ovary and placenta in human and animal, and include progestogens, glucocorticoids, mineralocorticoids, androgens and estrogens (Raven and Johnson, 1999). Estrogens (estradiol, estrone and estriol) are predominantly female hormones, which are important for maintaining the health of the reproductive tissues, breasts, skin and brain. Progestogens (progesterone) can be thought of as a hormonal balancer, particularly of estrogens. Androgens (testosterone, dehydroepiandrosterone and androstenedione) play an important role in tissue regeneration, especially the skin, bones and muscles. Glucocorticoids (cortisol) are produced by the adrenal glands in response to stressors such as emotional upheaval, exercise, surgery, illness or starvation. All the steroid hormones exert their action by passing through the plasma membrane and binding to intracellular receptors. In addition, there are some synthetic steroids such as ethynylestradiol (EE2) and mestranol (MeEE2) used as contraceptives.

All humans as well as animals can excrete hormone steroids from their bodies, which end up in the environment through sewage discharge and animal waste disposal. Those steroids have been detected in effluents of sewage treatment plants (STPs) and surface water (e.g. Desbrow et al., 1998, Kuch and Ballschmitter, 2001, Ternes et al., 1999a). They may interfere with the normal functioning of endocrine systems, thus affecting reproduction and development in wildlife (Jobling et al., 1998). The steroids of concern for the aquatic environment due to their endocrine disruption potential are mainly estrogens and contraceptives, which include 17β-estradiol (E2), estrone (E1), estriol (E3), 17α-ethynylestradiol (EE2) and mestranol (MeEE2) (Fig. 1).

Vitellogenesis (plasma vitellogenin induction) and feminisation in male fish have been observed in British rivers and are attributed to the presence of these estrogenic compounds Desbrow et al., 1998, Jobling et al., 1998. Concentrations as low as 1 ng/l of E2 led to induction of vitellogenin in male trout Hansen et al., 1998, Purdom et al., 1994. Hormone steroids in the environment may affect not only wildlife and humans but also plants Shore et al., 1995b, Lim et al., 2000. Alfalfa irrigated with sewage effluent, which contained hormone steroids, was observed to have elevated levels of phytoestrogens (Shore et al., 1995b).

In addition to estrogenic steroids, there is also a concern about the use of steroid drugs used as growth promoters in livestock (Schiffer et al., 2001). However, little research has been conducted on the fate of these steroids excreted by animals and their effect on wildlife and human health.

In this brief review, we provide an overview of sources, environmental concentrations in surface and ground water, and summarize the current knowledge on fate and behaviour of these steroid compounds.