J. W. Birkett
2.2 SPECIFIC SOURCES RELATING TO ENDOCRINE DISRUPTING CHEMICALS (EDCS)
2.2.5 S URFACTANTS
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 concen- trations 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.
46 Endocrine Disrupters in Wastewater and Sludge Treatment Processes
cleaners for machinery and materials, paints, pesticides, textiles, and in metal working and personal products. Table 2.6 indicates the sources and examples of concentrations of NP and its ethoxylates.
Table 2.6 shows that, in addition to industrial uses, there are many products containing NP and NPEOs that are used for domestic purposes. Thus, there are many possible entry routes into the environment for these substances during their manu- facture, use, and disposal.57
The range of uses of these compounds may also represent a direct source of human exposure. Examples include possible residues of NP and NPEOs in food as a result of the use of pesticides, vegetable and fruit waxes, and detergents and disinfectants used in food packaging.57 A recent study58 has found 4-nonylphenol in a range of foodstuffs, including breast milk and formula milk. The presence of this, and other xenoestrogens, in food provides further cause for concern because many of these synthetic chemicals have a tendency to bioaccumulate.
Cosmetic products such as makeup, skin creams, hair care products, and bathing products may also be direct sources of exposure to these compounds. An example is Nonoxynol – 9 (NP9EO), used as a spermicide in contraceptive products.57
There are no known natural sources of NP and NPEOs, and thus their ubiquitous presence in the environment is a result of anthropogenic activity. Annual worldwide production of alkylphenol ethoxylates is around 650,000 tons.58
Most of the NPEOs used in commercial and industrial formulations will be disposed of via sewers for treatment at sewage treatment works. During treatment, degradation processes lead to the production of metabolites and a shortening of the ethoxylate chain. These ethoxylates can be degraded to produce NP, which is con- sidered to be more persistent and toxic than the ethoxylates. This degradation process is discussed in greater detail in Chapter 4.
TABLE 2.6
Sources and Concentrations of Nonylphenol and Its Ethoxylates
Source Concentration
Detergents 0–28%
Deodorant 1–3%
Makeup 0.1–10%
Hair products 1–30%
Paints 0.6–3%
Paper processing effluents NP (0.02–26.2 µg L — 1), NPEOs (0.1 to 35.6 µg L-1)
STW effluents <0.02–330 µg L-1
Pesticides <1–20%
Food Nonylphenol (0.1–19.4 µg kg-1)
Data fromWhitehouse, P., Wilkinson, M., Fawell, J. K., and Sutton, A., Research and development Report No. Technical report P42, 1998; Environment Canada, Health Canada. Priority Substances List Assessment Report: Nonylphenol and its ethoxylates, 2000, pp. 134; andGuenther, K., Heinke, V., Theile, B., Kleist, E., Prast, H., and Raecker, T., Endocrine disrupting nonylphenols are ubiquitous in food, Environ. Sci. Technol. 36, 1676, 2002.
Sources of Endocrine Disrupters 47
Within the aquatic environment, concentrations of AP and APEOs have been detected. Concentrations of NP in the air of the New York–New Jersey Bight ranged from 2.2 to 70 ng m–3. 57
No data on the levels on NPEOs in air were identified, although as these compounds are far less volatile than NP, it is expected that they would not partition to the atmosphere. Levels of NPEOs and NP in effluents and waters vary greatly.
For example, concentrations of NP in textile mill and paper mill effluents ranged from 2.68 to 13.3 µg L–1 and <0.02 to 26.2 µg L–1, respectively.57 Concentrations of NPEOs from these industries were 2.07 to 8811 µg L–1 and 0.1 to 35.6 µg L–1, respectively. Moreover, highest freshwater concentrations of NP were observed in areas near STW discharges, pulp mill discharges, or regions of heavy industry. In the United Kingdom, effluent concentrations from STW range from <0.02 to 330 µg L–1.56 Surface water concentrations of NP vary dramatically across the U.K.
from <0.02 to 53 µg L–1.56 The highest value is from the River Aire and is thought to be related to the textile industry in the area. Within the sedimentary compart- ment, alkylphenols and their mono- and di-ethoxylates exhibit a significant asso- ciation. In sediments below effluent discharges, concentrations of up to 13.1 mg kg–1 of NP and up to 25 mg kg–1 of NP, nonylphenol ethoxylate (NP1EO), and nonylphenol diethoxylate (NP2EO) were detected.6,56 In U.S. rivers, sediments monitored for NP from 30 sites, downstream from industrial and municipal waste- water outfalls, ranged from not detectable to 2.96 mg kg–1. Much lower concen- trations of NP1EO were found (<0.0023 to 0.175 mg kg–1).59 Substantial concen- trations of NP and other products are found in the sludges from STWs. Disposal of this sludge to sea could reintroduce these compounds into the aquatic environ- ment. Moreover, the leaching of APs and ethoxylates from sludge disposal sites and the application of such sludge to agricultural land may result in potential contamination of the terrestrial environment.60
2.2.6 POLYAROMATIC COMPOUNDS
2.2.6.1 Polyaromatic Hydrocarbons (PAHs)
PAHs are formed from both natural and anthropogenic sources, largely by the incomplete combustion of organic materials. Natural sources of PAHs include forest fires,61 volcanic activity,61 stubble burning, and the release of petroleum hydrocarbons by marine seeps. According to Brown et al.,62 anthropogenic sources of PAHs can be classified as stationary or mobile. The stationary category incorporates a wide range of activities, such as residential and commercial heating and industrial pro- cesses (e.g., aluminum production and coke manufacture). Within the mobile cate- gory, petrol and diesel-engined vehicles are the predominant sources.
Stationary sources accounted for between 80 and 90% of total PAH emission prior to the 1980s, but recently mobile sources seemed to be the major contributors in urban and suburban areas.63 Anthropogenic sources are considered to be more important than natural sources as a contributor to the environment, and 95% of U.K. PAH emissions are from anthropogenic sources.64 Estimates in the United States have shown the annual emission of benzo(a)pyrene, a very toxic PAH, to
48 Endocrine Disrupters in Wastewater and Sludge Treatment Processes
be approximately 1300 tons.65 In the aquatic environment, PAHs can be formed by microbial synthesis from certain precursors.66 Like many semivolatile com- pounds, PAHs are widely distributed in the environment. Possible routes of entry to the aquatic environment include wet and dry deposition, direct and indirect discharges, and surface runoff. Total global PAH inputs to water from all sources has been estimated at > 80,000 tons per year.67
The principal sources of anthropogenic PAHs are the combustion of fossil fuels, aluminum smelting, refuse burning, coke ovens, petroleum processing, and vehicle emissions.61 Concentration of PAHs will also be related to the types of industries and other sources present, high levels being associated with heavy coal burning industries.65 In general, concentrations in urban and industrial areas are 10 to 100 times higher than those in rural areas.65.
Other sources of PAHs include sewage, sewage sludge, cigarette smoke, gas leakage, and fuel spills and leakage. Raw sewage or treated effluent may serve as the major point source of PAHs in lowland river systems.68 In raw sewage, PAHs are derived from three main sources: industrial and domestic effluent, urban runoff, and atmospheric pollution.69 Concentrations of individual PAHs in domestic raw sewage vary between 1.0 and 3520 ng L–1 during dry weather periods, and between 1840 and 16,350 ng L–1 during heavy rainfall, when urban runoff may increase PAH concentrations by up to two orders of magnitude.70 PAH concentrations found in sewage sludge vary between 1.6 and 6 mg kg–1. A survey of sewage sludge from 12 U.K. STWs found concentrations of individual PAHs ranging from 0.08 to 11.4 mg kg–1. The highest PAH concentrations are present in sewage sludge from treatment works serving industrialized areas.70
2.2.6.2 Polychlorinated Biphenyls (PCBs)
PCBs have been used in a wide variety of industrial applications because of their high stability and electrical resistance.7 They are used in dielectric fluids in trans- formers and capacitors, plasticizers and components of cement, hydraulic lubricants, cutting oils, flame retardants, plastics, paint and adhesives.46,71 Even though PCB production has been banned in most countries since the 1970s and 1980s, it is estimated that over 1 million ton of PCBs have been generated.7 About one third of this quantity is thought to be circulating in the environment.46
These compounds are known to be ubiquitous in the environment. Concentra- tions in the atmosphere are usually given in pg m–3, surface waters in ng L–1, birds eggs and fish fat in mg kg–1, and µg kg–1 in sediments.72 For example, concentrations in sediments are variable and range from 10s to 1000s µg kg–1, these values depend- ing on numerous factors, not least the industrial activity within the area. Because PCBs are expected to be sorbed to particulate matter,71 concentrations in the sediment compartment are more likely to be detectable. Sources to STWs are mainly from the atmosphere via wet deposition processes. Further discussion of the fate of PCBs in STW processes is given in Chapter 4.
Due to their high biostability and lipophilicity, PCBs have accumulated in food chains, especially in aquatic and marine species.73 Thus, sources of human exposure to PCBs are generally from food, particularly fish, fish products, and animal fats.
Sources of Endocrine Disrupters 49
2.2.6.3 Brominated Flame Retardants
Flame retardants are used in plastics, textiles, electronic circuitry, and other materials to prevent fires.74 Brominated compounds are used because of their ability to generate halogen atoms from the thermal degradation of the compound to chemically reduce and ”retard” the development of the fire.75 The types of brominated compounds utilized for this purpose are polybrominated biphenyls (PBB), polybrominated diphe- nylethers (PBDE), hexabromocyclododecane (HBCD), and tetrabromobisphenol A (TBBPA). These substances are persistent, lipophilic, and have been shown to bioaccumulate.76 Some of these additives do not chemically bind to the plastics or textiles and, thus, may leach from the products into the environment. TBBPA how- ever, does bind chemically to plastics and textiles.
These compounds are used worldwide and in vast quantities. Annual world production of flame retardants is approximately 600,000 tons, with 60,000 tons being chlorinated and 150,000 tons being brominated compounds.75 Of the brominated compounds, about one third contain TBBPA, another third contains various bromine compounds including PBBs, and the final third contains the PBDEs, predominantly decaBDE.75 In recent years, there has been a tendency to use higher order brominated compounds, such as the PBDEs. In these, the commercial formulations consist predominantly of mixtures of penta, octa, and decabromodiphenyl ethers. According to the International Programme on Chemical Safety published by the World Health Organization,77 there are eight world manufacturers of PBDEs. Regarding the annual consumption of these compounds, the majority is in the form of deca-BDE (30,000 tons), followed by octa-BDE (6000 tons), and penta-BDE (4000 tons).78 Table 2.7 summarizes the potential sources of brominated flame retardants.
The main source of flame retardants, particularly the PBDEs, is likely to come from waste from the products they are used in. This waste is either incinerated or disposed of at landfills. Despite data gaps in this area of study, incineration and landfills are thought to be potential sources of release of PBDEs into the environment.75
TABLE 2.7
Sources of Brominated Flame Retardants
Source Brominated Flame Retardant
Plastics PBDE, HBCD, TBBPA
Textiles PBDE, HBCD, TBBPA
Electronic appliances PBDE, HBCD, TBBPA
STW discharges and sewage sludge PBDE, HBCD, TBBPA
Paint PBDE
Cars PBDE, TBBPA
Breast milk PBDE
Meat, eggs, fish PBDE, TBBPA
Data fromSellstrom U, Determination of some polybrominated flame retardants in biota, sediment and sewage sludge, PhD dissertation, Stockholm University, 1999; Oberg, K., Warman, K., and Oberg, T., Distribution and levels of brominated flame retardants in sewage sludge, Chemosphere, in press, 2002.
50 Endocrine Disrupters in Wastewater and Sludge Treatment Processes
Brominated flame retardants are used in the plastics industry to produce a variety of products, including common plastics, polymers, and resins. Concentrations of these additive flame retardants vary between 5 and 30%, depending on the applica- tion.75 Many of these compounds are also used in electronic components such as circuit boards, computers, televisions, electrical cables, and capacitors, most of which are found in homes. These substances are also present in upholstered furniture, textiles, car cushions, insulation blocks, house wall materials, and packaging mate- rials.76 Daily contact with these substances raises concern over the level of exposure of humans to brominated flame retardants. Watanabe et al.81 found mainly deca-BDE in airborne dust from the Osaka region in Japan, and various tri-, tetra-, penta-, and hexa-BDEs were detected in samples from Taiwan and Japan, taken in the vicinity of metal recycling plants.82 Concentrations ranged from 23 to 53 pg m–3 in Taiwan and 7.1 to 21 pg m–3 in Japan. A study of indoor air quality83 revealed that PBDEs were detected in an electronics plant and office environments. Concentrations in the electronics plant were 400 to 4000 times higher than in the office environments. The presence of these substances in air shows that brominated flame retardants are leaking into the indoor environment from electronic appliances and exposing humans.
In the aquatic environment, flame retardants tend to accumulate in the sediments because they are highly lipophilic and have low water solubilities. A study of river, estuarine, and marine sediments84 found deca-BDE, octa-BDE, hexa-BDE, penta- BDE, and tetra-BDE to be present in all samples. Concentrations of deca-BDE were in the range <25 to 11,600 µg kg–1 dry weight. The other compounds present ranged from below the limit of detection to 70 µg kg–1 dry weight. Analysis of sediments from European rivers revealed high concentrations of PBDEs in the River Mersey (1700 µg kg–1) and in Belgium on the River Schelde (200 µg kg–1). Most samples had levels below 20 µg kg–1. In the United States, Lake Michigan is considered to be heavily contaminated with PBDEs.85 Analysis of fish from the lake86 revealed concentrations of PBDEs from 44 to 149 µg kg–1. In southern Virginia several species of fish from the Roanoke and Dan rivers contained PBDE concentrations greater than 1 part per million (ppm).87 Analysis of fish from Europe has also shown the presence of PBDEs at concentrations similar to and higher than those found in the U.S.75 These levels in fish clearly indicate that brominated flame retardants are an environmental concern and raise issues regarding the advisability of consuming fish and other foodstuffs that may be contaminated. Levels of PBDEs have also been detected in dairy products, breast milk, meat, and eggs.75
Sewage sludge concentrations of brominated flame retardants reflect the usage and exposure within society, because sources may be households, industries, traffic, and other nonpoint sources.79 All the brominated flame retardants (i.e., PBDE, HBCD, TBBPA) have been found in sewage sludge samples.79 Oberg et al.80 analyzed 116 sewage sludge samples from 22 wastewater treatment plants for brominated flame retardants. Concentrations of PBDEs were in the range of not detectable (n.d.) to 450 µg kg–1 and TBBPA between n.d. and 220 µg kg–1. Significant variation between plants was observed, indicating influence from indus- tries and other local sources.
According to Wenning,88 there may be as many as five different sources of PBDEs:
Sources of Endocrine Disrupters 51
1. Releases from manufacturing processes using PBDEs currently manufac- tured by industry
2. Releases from past manufacturing activities using PBDEs that are no longer manufactured, but may be persistent in the environment
3. Natural debromination of the higher brominated congener mixtures 4. Natural sources of brominated compounds78
5. Anthropogenic inputs of organobromine compounds from sources other than the flame retardant industry, such as mineral ore mining and deep- well injection in the petroleum industry
These sources, together with the other potential sources discussed, are responsible for the ubiquitous nature of brominated flame retardants in the environment today.