Endocrine disrupting compounds (EDCs) are a particularly dangerous group because they have estrogenic activity. Among EDCs, the alkylphenols commonly used in households deserve attention, from where they go to sewage treatment plants, and then to water reservoirs.
1. Introduction
Environmental pollution has become a major challenge in recent years due to increasing population, urbanization, and industrialization
[1]. The priority is to find the sources of EDCs and the routes by which they enter the aquatic environment.
EDC has been detected in a variety of fresh, brackish, and marine ecosystems. Due to their physical and chemical properties, EDCs can bioaccumulate, biomagnify, are persistent, and are very toxic to aquatic organisms, both for plants and animals
[2].
These compounds are released into the environment from a variety of sources, primarily municipal and industrial waste, agricultural practices, animal waste, and sewage treatment plants (STP)
[3]. Most of the packaging for food, cosmetic products, solvents, preservatives, and pesticides is also made of EDC-containing materials
[2][4][5].
Long-term use of EDC, regardless of the concentration level, may accumulate in animals and be partially released into the environment through animal feces. In fish and the largest consumers of the food web, the rate of bioaccumulation is higher because most EDCs are lipophilic and concentrated in the fat of the consuming organisms
[6]. Therefore, these substances will penetrate the food chain and ecosystems, potentially adversely affecting human health.
In agriculture, non-metabolized and non-degradable compounds in animal fertilizers still have active metabolites, reducing the quality of surface and groundwater and significantly affecting aquatic life. In water, EDCs undergo biodegradation and chemical and photochemical degradation, dilution, and sorption to sediments, which partially leads to their elimination from aquatic ecosystems
[2][7][8][9].
2. Nonylphenol
The presence of nonylphenol in the environment is clearly correlated with anthropogenic activities such as sewage treatment, storage, and recycling of sewage sludge. NPEOs are used as non-ionic surfactants in industry (cellulose and paper, textiles, agriculture, metals, plastics, petroleum refining), in households in the form of detergents, solubilizers, and personal care products in non-EU countries
[10][11]. Nonylphenol is a xenobiotic compound used in the production of antioxidants, additives to lubricating oils and in the production of ethoxylated surfactants nonylphenol, which is its main use (65%)
[12].
As surfactants, NPs are used in cleaning agents, so their primary source in the environment are discharges of wastewater from industrial and municipal wastewater treatment plants (WWTPs), as well as land enriched with solid sewage or manure, runoff from pesticides and fertilizers on agricultural fields, and fodder livestock. Due to their cheapness, NPEO surfactants are used in various areas, for example in agricultural pesticides where surfactant is added to control the properties of pesticides
[13][14].
Inadequately treated domestic sewage causes high concentrations of NP in the aquatic environment. The levels of NP depended on the size of NP discharges into the river, temperature, flow velocity, biodegradation, etc. About 60% of NP and its derivatives produced in the world ends up in water supply
[15][16][17]. In addition, the presence of NP is observed in polyvinyl chloride (PVC), which can contaminate water passing through PVC plumbing
[18].
Technical NP is the major form of NP that is released into the environment. Technical nonylphenol consists of a mixture of more than one hundred isomers that have an alkyl moiety attached at various positions on the phenolic ring, with para-substituted NP (4-NP). However, in the environment, the proportions of isomers may be different
[13][19][20].
Due to its high hydrophobicity, resistance to biodegradation and low solubility, NP tends to accumulate in various environmental matrices
[21]. NP can evaporate into the atmosphere from wastewater discharges, wastewater treatment plant (liquids and sludge) or heavily contaminated surface waters. NP binds to the aerosols generated by the wastewater treatment plant, leading to a reduction in air quality in the vicinity of STW. From the atmosphere, NP may re-enter aquatic and terrestrial ecosystems with rain and snowfall
[12].
The concentration of nonylphenol in the surface layers of natural waters may decrease due to photolysis induced by sunlight
[7][22]. Biodegradation of NPs is difficult due to physicochemical properties such as low solubility and high hydrophobicity. NP accumulates in environmental compartments that are characterized by a high content of organic substances, usually sewage sludge and river sediments. NP occurs in river waters in concentrations up to 4.1 μg/L and 1 mg/kg in sediments
[15][16][23]. The concentration of NP in the water and sediments are shown in
Table 1.
Table 1. The Bisphenol A (BPA) and nonylphenol (NP) concentrations in aquatic environments.
Environment |
BPA |
NP |
Location |
References |
Surface water |
nd–376.6 |
117–865 |
China, Pearl River Delta |
[24][25] |
15.80–110.38 |
nd–104.02 |
China, Honghu Lake |
[26] |
16.3–30.1 |
- |
Poland, Vistula river |
[27] |
0.71–47.40 |
- |
Philippines, Laguna Lake |
[28] |
Groundwater |
nd–35.54 |
5,6 |
China |
[29][30] |
1–629 |
- |
Poland |
[27] |
Wastewater treatment plants |
IW |
nd–5927.5 |
nd–9560 |
Poland |
[27] |
EW |
nd–190 |
nd–9560 |
IW |
234.6–1527.1 |
519.6–4183.4 |
China |
[31] |
EW |
3.1–623.6 |
13.4–471.6 |
Seawater |
10.6–52.3 |
22–201 |
Greece, Thermaikos Gulf, Northern Aegean Sea |
[32] |
240 |
730 |
Japan, Tokyo Bay coastal area |
[33] |
Sediment |
W |
7.02–13.95 |
- |
China, Erhai Lake |
[34] |
S |
11.09–63.46 |
- |
W |
- |
75.4 |
Germany, Luppe River |
[35] |
S |
- |
22,342.6 |
W |
nd–37,000 |
- |
Indonesia, Mahakam River |
[36] |
S |
nd–952.6 |
- |
W |
<1.3–5.2 |
nd |
New Zealand, Lyttelton Harbour |
[37] |
S |
<0.4–9.9 |
nd |
W |
5.0–277.9 |
4.0–1721 |
Poland, Gulf of Gdańsk (southern Baltic Sea) |
[38] |
S |
2.64–60.20 |
0.08–1001 |
Drinking water |
6–53 |
- |
Poland |
[27] |
2.6–6.2 |
1.7–3.9 |
Serbia, rural area |
[39] |
2.5–35.6 |
1.2–7.9 |
Serbia, urban area |
[39] |