S TEROIDS - SPECIFIC SOURCES RELATING TO ENDOCRINE DISRUPTING CHEMICALS (EDCS)

J. W. Birkett

2.2 SPECIFIC SOURCES RELATING TO ENDOCRINE DISRUPTING CHEMICALS (EDCS)

2.2.1 S TEROIDS

38 Endocrine Disrupters in Wastewater and Sludge Treatment Processes

The main sources of groundwater pollution arise from industrial, domestic, and agricultural sources. Industrial sources are industrial effluents, accidents (e.g., leakage from pipes and tanks), and rainwater that infiltrates and percolates through solid waste deposits. Solid wastes are deposited in landfill sites. Landfills that take hazardous waste are often sited in areas where there are impermeable strata, such as clay, or where clay linings have been deliberately installed to prevent leachate from escaping.

Domestic sources of groundwater pollution fall into more or less the same categories as the industrial sources. Leakage from septic tanks and percolation of rainwater through landfills containing domestic refuse are the main risks.

Agricultural sources are potentially the most dangerous because they are nonpoint sources, and percolation through soils into the groundwater can occur over wide areas.

As a result, fertilizers, minerals, herbicides, and pesticides can all enter aquifers.

There is also a potential risk from the disposal of sewage sludge on agricultural land, which, in addition to the sea, is another major disposal outlet for this material.

Endocrine disruption manifesting as reproductive and behavioral abnormalities observed in fish has been primarily attributed to EDCs in sewage effluent discharged into watercourses. In addition to the types of discharges already mentioned, contamination of the aquatic environment can be caused by numerous other sources.

These sources of EDCs are summarized in Table 2.2.

2.1.5 OTHER SOURCES

For the human population, the most important source of EDCs by far is food. Some of these compounds are utilized in food production and packaging, which has prompted concern that diet may be an exposure route for EDCs.²⁰ Examples of this include pesticide residues on fruit and vegetables, use of plastic wrapping, and the leaching of compounds from can linings.²¹ These, together with other sources for EDCs, are highlighted in the following section.

2.2 SPECIFIC SOURCES RELATING TO ENDOCRINE

Sources of Endocrine Disrupters39 TABLE 2.2

Sources of Endocrine Disrupting Chemicals (EDCs) Entering Watercourses

Source of EDCs Receiving Waters Source Method EDCs Likely to Be Present

Domestic sewage effluent Surface water^a Point Steroid estrogens,² Surfactants,³ PAEs, BPA⁴

Groundwater Nonpoint

Groundwater Point (recharge)

Industrial sewage effluent Surface water Point Surfactants,^5,6 PAHs,⁷ PCBs,⁷ PBDEs,⁸ pesticides,⁷ PAEs,⁴ BPA

Groundwater Nonpoint

Industrial discharges Surface water Point Dioxins, PBDEs,⁸ TBBA, ⁹ PAEs, PCBs,⁷

PAHs,⁷ pesticides,⁷ BPA⁴

Groundwater Nonpoint

Paint applied to boats Surface water Point TBT¹⁰

Agricultural runoff (crops) Surface water Nonpoint Pesticides,⁷ APs, APEs,¹¹ PBDEs,¹² PAHs^13,14

Groundwater Nonpoint

Agricultural runoff (animals) Surface water Nonpoint Steroid estrogens^15,16

Groundwater Nonpoint

Recreational/Urban runoff Surface water Nonpoint Pesticides, PAHs⁷

Groundwater Nonpoint

Leachate from waste dumps Groundwater Nonpoint PAHs,¹⁷ PBDEs, TBBA,⁹ BPA, PAEs

Deposition from the air Surface water Nonpoint PAHs,⁷ PCBs, PCDDs, PCDFs, PBDEs,¹⁸

TBBA, pesticides

Groundwater Nonpoint

Natural Surface water Nonpoint PAHs, steroid estrogens (natural)¹⁹

Groundwater Nonpoint

Phthalate acid esters (PAEs); bisphenol A (BPA); polyaromatic hydrocarbons (PAHs); polychlorinated biphenyls (PCBs); polybrominated diphenyl ethers (PBDEs); tetrabromobisphenol A (TBBA); tributyltin (TBT); polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs)

aSurface waters include streams, rivers, estuaries, and seas

40 Endocrine Disrupters in Wastewater and Sludge Treatment Processes

Detectable concentrations of steroid hormones (e.g., estradiol, estrone, progesterone, testosterone) have also been found in fish, poultry, eggs, pork, cheese, milk, and milk products.²³ However, in comparing the production of these hormones in adults and children with their daily intake, it is found that children, who have the lowest hormone production rate, show levels of progesterone to be 20 times greater then their intake, while estradiol and testosterone production levels are 1000 times higher.²³ It is likely that no hormonal effects in humans can be expected from naturally occurring steroid compounds in food. However, use of synthetic EDCs and the presence of xenoestrogens in foodstuffs may be more problematic.

Within the steroid hormone group, it is perhaps the natural (estrone [E1], 17β- estradiol [E2], estriol [E3]) and synthetic (ethinylestradiol [EE2], mestranol) steroid estrogens that have received the most scientific attention. These compounds are the major contributors to the estrogenic activity observed in sewage effluent^24,25 and the receiving water body (see Chapter 6). Their presence in the aquatic environment is attributed to their incomplete removal during the sewage treatment process.²⁶ Although concentrations of steroid estrogens have been reported in the low ng L^–¹ levels, their estrogenic potency warrants cause for concern, as EE2 has been shown to induce vitellogenin (VTG) production (a female yolk protein) in male fish at 0.2 ng L^–¹.²⁶

The presence of steroid estrogens in STW effluent arises from mammalian excretion, in particular females of reproductive age and those who are pregnant.

Women excrete 10 to 100 µg of estrogen per day depending on the phase of their cycle, and pregnant women can excrete up to 30 mg per day.²⁷ The major excretion product is estriol, with daily excretion rates for women at a maximum of 64 µg per day. The excretion rate of estrone and 17β-estradiol is 3 to 20 µg and 0.5 to 5 µg per day, respectively.²⁸ The majority of these estrogens are excreted from the human body within urine in a biologically inactive, conjugated form (predominantly as glucuronides and sulfates). However, because free estrogens have been observed in STW effluent, this implies that deconjugation has occurred at some stage during or prior to sewage treatment.²⁹ Moreover, the amount of natural and synthetic estrogens entering the STW is unlikely to decrease due to the origin and use. Steroid estrogens have also been detected in sewage sludge. Concentrations of estradiol, estrone, and estriol in sewage sludge from 14 different STWs in the United States range from

TABLE 2.3

Sources of Steroid Hormones

Source Steroid Hormone

Food — meat, fish, eggs, pork, dairy products Estradiol, estrone, progesterone, testosterone Sewage treatment work effluents Estradiol, estrone, estriol, ethinyl estradiol Sewage sludge Estradiol, estrone, estriol, ethinyl estradiol

Oral contraception Ethinyl estradiol, mestranol

Hormone replacement therapy (HRT) Conjugated estrone, 17α and 17β-estradiol

Runoff Estradiol, estrone

Agricultural waste Estradiol, estrone

Sources of Endocrine Disrupters 41

0.01 to 0.08 ng L^–¹, while mean concentrations of ethinyl estradiol in raw and treated sewage were 1.21 ng L^–¹ and 0.81 ng L^–¹, respectively.¹⁹ The application of such sludge to agricultural land is likely to increase the estrogen content from other sources, such as runoff.

The main uses of synthetic estrogens are in oral contraception and hormone replacement therapy (HRT). In 1990, of the 58 million women in the United States who actively practiced contraception, 10 million used oral contraception.¹⁹ These contraceptives contain a combination of estrogen and progestin, with the active ingredient being ethinyl estradiol (EE2), or sometimes mestranol. Typical concentrations of EE2 range from 20 to 50 µg, with 35 µg the most commonly prescribed.

It is estimated that of the 40 million menopausal American women, 5 to 13 million are using HRT.³⁰ The active ingredients in HRT drugs are the conjugated equine estrogens, as well as conjugated estrone and 17 α and 17β-estradiol,¹⁹ with a typical daily dose of conjugated estrogens of 0.625 mg. Arcand-Hoy et al.¹⁹ produced an estimated introduction concentration (EIC) of EE2 into the aquatic environment, based on the amount of pharmaceuticals sold in the United States. The EIC for EE2 was found to be 2.16 ng L^–¹.

Intensive farming practices also produce appreciable concentrations of estrogens.

The concentration of estradiol in runoff and in the soil from land fertilized with broiler litter has been measured and demonstrates sizeable “edge of field” losses.¹⁶A study of effluent concentrations³¹ detected the highest concentrations of estrogens from agricultural settlements.

2.2.2 PHYTOESTROGENS

Phytoestrogens are plant-derived compounds that possess estrogenic activity. The term phytoestrogen is used to define a class of compounds that are nonsteroidal and are generally of plant origin, or are produced by the in vivo metabolism of precursors that are present in several plants consumed by humans.³² This metabolism process results in the production of heterocyclic phenols, with a structure similar to the steroid estrogens.³³ Isoflavones and lignans are the two main classes of these compounds. The main source of phytoestrogens is food. Isoflavones are found in a variety of plants, including fruits and vegetables, and are especially abundant in soy products.³⁴ Lignans are present in whole grains, legumes, vegetables, and seeds, with high concentrations of lignans found in flaxseed. Table 2.4 indicates the main food sources for both these phytoestrogens.

Phytoestrogens have many structural similarities to 17β-estradiol and are more potent in vitro than many of the man-made chemicals tested to date.³⁵ This has raised concern over exposure to phytoestrogens from dietary regimes, particularly those with a high proportion of soy products, typical of diets in Asia and the far East. On consuming products containing phytoestrogens, there are several possible pathways:

1. Excretion 2. Absorption

3. Transformation to other compounds

42 Endocrine Disrupters in Wastewater and Sludge Treatment Processes

It appears that these compounds are easily metabolized, spend little time in the body, and are not stored in tissues, unlike some synthetic EDCs (e.g., PCBs).

Moreover, diets rich in phytoestrogens have been linked to beneficial health effects.

Evidence shows that phytoestrogens may potentially confer health benefits related to cardiovascular diseases, cancer, osteoporosis, and menopausal symptoms.³⁴ These potential health benefits are consistent with the epidemiological evidence that rates of heart disease, various cancers, osteoporotic fractures, and menopausal symptoms are lower among populations that consume plant-based diets, particularly among cultures with diets that are traditionally high in soy products.³⁴ For example, Asian populations suffer significantly lower rates of hormone-dependent cancers compared to Westerners.³⁶ This suggests that phytoestrogens may have some beneficial effects against such cancers. Certainly as diet patterns change, the risk for certain hormon- ally related diseases will also change. The difference in diet patterns in the East and West with regard to consumption of phytoestrogens is significant. Asian populations consume between 20 and 80 mg/day of genistein, which is almost entirely derived from soy, whereas intakes have been estimated at 1 to 3 mg/day in the United States.³⁷ 2.2.3 ORGANO OXYGEN COMPOUNDS

2.2.3.1 Bisphenol A

Bisphenol A (BPA) is manufactured in large quantities, with over 90% being used in the plastics industry for the production of polycarbonate and epoxy resins, unsat- urated polyester–styrene resins, and flame retardants.³⁸ The plastics produced are used in food and drink packaging, such as for lining metal food cans, for bottle tops, and water supply pipes.⁴ Other uses include additives in thermal paper, powder paints,

TABLE 2.4

Sources of Phytoestrogens

Isoflavones Lignans

Soybeans Flaxseed

Lentils Wheat

Beans Oats

haricot Bran

broad Garlic

kidney Asparagus

lima Carrot

Chick peas Broccoli

Wheat Mushroom

Barley Pear

Hops Plum

Rye Banana

Bran Orange

Oats Apple

Rice Strawberry

Sources of Endocrine Disrupters 43

in dentistry,³⁹ and as antioxidants in plastics.^38,40 Almost 30% of the world’s production is within the European Union, with reportedly 210,000 tons produced in Ger- many in 1995.³⁸

Studies²¹ have shown that bisphenol A, when present in food can linings, can leach into the product and acquire estrogenic activity. Cans containing the highest amount of bisphenol A result in about 80 µg kg^–¹ of the canned food.²¹ The exper- imental values are clearly below the EU limit of migration for bisphenol A in food cans of 3 mg kg^–¹. Other studies have also shown bisphenol A to leach from cans into vegetables.^41,42

Because bisphenol A is used widely in households and industry, it is expected to be present in raw sewage, wastewater effluents, and in sewage sludge.⁴ Fromme et al. ³⁸ found low concentrations of BPA in surface waters (0.0005 to 0.41 µg L^–¹), sewage effluents (0.018 to 0.702 µg L^–¹), sediments (0.01 to 0.19 mg kg^–¹), and sewage sludge (0.004 to 1.363 mg kg^–¹). The release of BPA into the environment can occur during manufacturing processes and by leaching from the final product.

With mean concentrations in landfill leachates of 269 µg L^–¹, they may be a significant source of the bisphenol A found in the environment.⁴³ Industrial sources, however, are thought to be the major source of this chemical environment.⁴

2.2.3.2 Phthalates

Phthalates have been in use for almost 40 years and are used in the manufacture of PVC and other resins, as well as plasticizers and insect repellents.³⁸ Plasticizers are used in building materials, home furnishings, transportation, clothing, and, to a limited extent, in food packaging and medicinal products.⁴⁴ There is also concern regarding the potential health effects of several phthalates because these compounds are used to impart softness and flexibility to normally rigid PVC products in children’s toys.⁴⁵ Phthalates can enter the environment through losses during manufacture and by leaching from the final product. This is because they are not chemically bonded to the polymeric matrix.³⁸ These compounds have low water solubilities and tend to adsorb to sediments and suspended solids.

Of the phthalates, di (2-ethylhexyl) phthalate (DEHP) is one of the most significant because it is used as a plasticizer in large quantities. For example, in Germany in 1994/1995, 400,000 tons of phthalates (DEHP 250,000 tons; dibutylphthalate [DBP] 21,000 tons; butylbenzylphthalate [BBP] 9000 tons) were produced.³⁸ Regard- ing environmental concentrations, DEHP tends to give the highest phthalate concentrations, ranging from 0.33 to 97.8 µg L^–¹ in surface waters, 1.74 to 182 µg L^–¹ in sewage effluents, 27.9 to 154 mg kg^–¹ in sewage sludge, and 0.21 to 8.44 mg kg^–¹ in sediments.³⁸ Concentrations of DBP and BBP have been detected in much lower concentrations. Other sources exhibiting low concentrations of these substances, such as runoff from municipal and industrial dump sites, should not be overlooked.

2.2.3.3 Dioxins

The term dioxins is used to represent seven of the polychlorinated dibenzodioxins (PCDDs) and 10 of the polychlorinated dibenzofurans (PCDFs). These substances

44 Endocrine Disrupters in Wastewater and Sludge Treatment Processes

are not produced commercially but are formed as by-products of various industrial and combustion processes.⁴⁶ Globally, the most important source is incineration of municipal, hospital, and hazardous wastes.⁴⁶ Other sources include fuel combustion, the steel and nonferrous metal industry, and the paper and pulp, cement, and glass industries.⁴⁶ According to Stangroom et al.,⁷ there are four major sources of PCDDs and PCDFs involving incineration processes: waste incineration, power generation by coal burning, domestic heating with wood or coal, and motor vehicle internal combustion. In 1995, the PCDD/F air emissions in Europe (17 countries) were estimated to have been 6500 g I-TEQ (international toxic equiv- alents) per year.⁴⁶

Dioxin exposure to humans arises from food, specifically from eating the fats associated with consuming beef, poultry, pork, fish, and dairy products. However, concentrations of these compounds are low and current average daily intakes for Europeans and Americans appear to be within the WHO recommended values of 1 to 4 pg of I-TEQ kg^–¹ of body weight.⁴⁷ The main route by which dioxins reach most watercourses is through soil erosion and stormwater runoff from urban areas. The strong binding of dioxins to organic matter⁴⁸ also supports the hypothesis that transport to watercourses may occur in association with soil particles. Industrial discharges can also significantly increase water concentrations near the point of discharge to rivers.

2.2.4 ORGANOTIN COMPOUNDS

Organotins are a group of organometallic compounds which were first produced in the 1930s. Since the 1960s, the commercial production and use of these compounds, including tributyltin (TBT) has increased dramatically, particularly for use in antifouling agents applied to boats. Despite legislative restrictions on the use of organotins in numerous countries, these pollutants have been detected in all environmental compartments and still represent a risk to the aquatic and terrestrial ecosystems.

One of the most important applications of organotins is the use of the mono- and di-alkyl tin compounds (MBT and DBT) as heat and light stabilizers in PVC processing, as their addition prevents the discoloration and embrittlement of the PVC polymer.⁴⁹ The biocidal properties of mainly TBT species have also led to their widespread use as an antifouling agent and as a general wood preservative. Other uses and potential sources arise from agrochemical use, materials and textiles processing, household products, and foodstuff packaging.⁴⁹ Table 2.5 gives some examples of organotin compound sources.

The world’s production of organotins has been estimated to be 50,000 tons per year.⁵⁰ About 70% of this is utilized in the plastics industry as stabilizers and as catalysts for polyurethane foams and silicones.⁴⁹ Several studies have shown that leaching of these organotin components from PVC materials has resulted in the contamination of food, beverages, drinking water, municipal water, and sewage sludge.^51–53 Another study⁵⁴ analyzed plastic household products and found butyltin compounds in 50% of these products. Baking parchments, polyurethane gloves, sponges, and cellophane wrap were among those “contaminated.” Moreover, these compounds were also seen to be transferred to food, by the analysis of cookies

Sources of Endocrine Disrupters 45

baked on the tested parchment. This has obvious implications for human exposure to these compounds.

As a result of the use of antifouling formulations containing TBT, the leaching of this compound from ships has produced severe effects on wildlife in the marine environment (see Chapter 1, Section 1.1). For example, a large commercial ship, leaching TBT at a constant rate, can release more than 200 g TBT per day into the immediate waters, and this can rise to 600 g if the vessel has been freshly painted.⁵⁵ This can result in a TBT concentration of 100 to 200 ng Sn l^–¹. Smaller estuaries and marinas have typical TBT concentrations of 10 to 70 ng Sn l^–¹.

A significant proportion of these compounds in the environment probably comes from agricultural and biocidal applications. They are generally applied by spraying, which results in contamination of the soil and surface waters due to leaching and runoff. The use of organotins as wood preservatives involves the application of a 1 to 3% solution in an organic solvent.⁴⁹ Processes used include dipping, spraying, and brushing, which may leave the wood prone to leaching these compounds.

However, the timber industry often utilizes a technique called double vacuum impregnation, which produces negligible leaching.⁴⁹

Concentration of these compounds and their metabolites has been observed in all parts of the aquatic environment, with compounds entering the environment by various routes, as discussed previously. Atmospheric concentrations of organotins are negligible, so this source is unlikely to be significant. Many of these compounds have industrial applications, and therefore influents at STWs may contain concentrations arising from non-antifouling uses of organotins, as well as possible runoff from pesticide application. Thus, inputs from wastewater and sewage sludge as well as the leachate from landfills must be considered as sources of these compounds.

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