Page 189 - Soil and water contamination, 2nd edition

176 Soil and Water Contamination

9.7.3 Endocrine-Modulating Chemicals
Endocrine-Modulating Chemicals (EMCs) (also called endocrine disruptor chemicals or
endocrine toxicants) are substances that interfere with the normal function of the endocrine
or hormone system. Consequently, they may cause serious adverse health effects, such as
cancer, reproductive and developmental defects, or altered immune function in an organism
or its progeny. EMCs include hormones (e.g. natural and synthetic oestrogens), surfactants,
pesticides, plasticisers, polychlorinated biphenyls ( PCBs), and dioxins/furans. These
substances or their ingredients possess a wide range of physical and biochemical properties:
some are lipophilic and persistent, while others are hydrophilic and rapidly degraded. Routes
of EMC exposure include intake of medication, ingestion of contaminated food products
and water, contact with contaminated soil and dust, and contact with plastic household
products (e.g. packaging, rainwear, footwear, carpets, and toys). Note that for the majority
of chemicals in use today, the long-term effects of exposure on the endocrine system are
unknown.
For aquatic ecosystems, the occurrence of all EMCs is of concern, but the most intensely
investigated EMCs are oestrogens, which mimic or inhibit the effects of the vertebrate female
reproductive hormones (e.g. Campbell et al., 2006). The major source of oestrogens in
surface water is the effluent from municipal and industrial wastewater treatment facilities.
The actual primary source of oestrogens entering the wastewater is humans who excrete
or dispose of natural hormones and pharmaceutical oestrogens (e.g. birth control pills) in
toilets. Conjugated oestrogens, which are formed when the body eliminates oestrogens,
are not oestrogenically active. However, in wastewater treatment systems, these conjugated
oestrogens can be deconjugated, liberating active oestrogenic compounds in the discharge.
The largest part of the oestrogens will be removed by degradation or sorption in the
wastewater treatment process, but when sewage sludge is applied to land, pharmaceutical
oestrogens may enter surface waters through runoff and groundwater flow. Oestrogens
are readily degradable and have relatively short environmental half-lives under aerobic
conditions. Under anaerobic conditions, however, they degrade slowly. Since many
oestrogens have moderately to high log Koc values, the mass that does not remain dissolved
is rapidly sorbed to organic matter in bed or suspended sediments, or ends up in organic
complexes.
Similarly, steroid oestrogens present in wastewater treatment plant effluents cause
feminising effects in fish, i.e. skewed male-to-female ratios and an increase in individuals of
indeterminate sex. Disturbance of the development and expression of sexual characteristics
in amphibians, reptiles and mammals has also been confirmed in laboratory studies.
However, it is still not well understood to what extent EMCs affect the sexual characteristics
and reproductive capabilities of natural populations (Wright-Walters, 2009).
9.7.4 Microplastics

As noted above, microplastics are plastic (i.e. synthetic, organic polymers of high molecular
mass) particles smaller than 1 or 5 mm. They can be subdivided into three groups according
to their source: primary microplastics, secondary microplastics and synthetic textile fibres.
Primary microplastics are microplastics produced either for direct use, for example as
industrial abrasives or in cosmetics, or for indirect use as raw material for the production
of plastic products (pre-production plastic pellets or nurdles). Primary plastics enter
the environment mainly due to accidental spills during transport or storage. Secondary
microplastics are formed in the environment as a consequence of the breakdown of larger
plastic material. As plastics are barely biodegradable, the breakdown of plastics into small
fragments is mainly due to mechanical abrasion, oxidative degradation or sunlight-driven

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