Chemicals and tonnage collection
For an evaluation of the EUSES modelling for AS, the most common Carbon-chains (C12, C14 and C16) with the highest tonnage contribution were collected. Odd numbered C-chains (C11, C13, C15), C-chains above C16 and below C10 are less common and so do not significantly influence the total amount of AS in Europe, therefore the EUSES calculations were conducted only for C12, C14, and C16 homologues (for a qualitative sensitivity analysis see the discussion section below ).
For the chain lengths C12, C14 and C16 tonnages were anonymously collected from the registrants of the REACH AS consortium with a production volume of >100 t/a. The homologue distribution was collected from the following even-numbered C-chain, linear AS substances: Sodium dodecyl sulfate (CAS No. 151-21-3); Sulfuric acid, mono-C12-14-alkyl esters, sodium salts (CAS No. 85586-07-8); Sulfuric acid, mono-C12-16-alkyl esters, sodium salts (CAS No. 73296-89-6); Sulfuric acid, mono-C12-18-alkyl esters, sodium salts (CAS No. 68955-19-1); Sulfuric acid, mono-C16-18-alkyl esters, sodium salts (CAS No. 68955-20-4); Sulfuric acid, mono-C12-14-alkyl esters, compds. with triethanolamine (CAS No. 90583-18-9); Sulfuric acid, mono-C12-14-alkyl esters, compds. with ethanolamine (CAS No. 90583-16-7); Sulfuric acid, mono-C12-14-alkyl esters, ammonium salts (CAS No. 90583-11-2).
In addition, the volumes of AS as constituents of Alkyl Ether Sulfates (AES) were collected from 15 high tonnage EU REACH registrants (>100 t/a), as AS are constituents of AES (from incomplete ethoxylation reaction, i.e. EO = 0) at concentrations between 10 - 35 % with 20 % as a realistic average. The AS volumes in technical AES represents a major amount of the total AS anionic surfactants concentrations since the production volume of AES exceeds that of AS by a factor of ten (IHS, 2016).
All registrants of the AS consortium responded to the tonnage survey. For the AES substances, 14 of 15 registrants replied. The missing information was substituted by an average tonnage reported by all tonnage information from the AES registrants.
The tonnages (from 2016) reported by the various companies were summed leading to a total tonnage of ~ 178,400 t (Table 1).
Table 1 Overview tonnage per chain length
Chain length
|
C 12
|
C 14
|
C 16
|
Overall
|
AS (t/a)
|
45,280
|
15,793
|
5,200
|
66,273
|
AES (t/a)
|
82,973
|
28,689
|
496
|
112,158
|
Total (t/a)
|
128,253
|
44,482
|
5,696
|
178,431
|
Use pattern
The tonnage information for the C12, C14 and C16 AS were assigned to the different uses as reported to ECHA in the C12 AS, Na (CAS-No. 151-21-3), registration dossier of 2010 (Table 2). Use information was obtained from the latest use maps provided by the relevant industry sector associations. The main application fields of AS are the household/ cleaning sector (AISE), the personal care sector (Cosmetics Europe), the construction sector (EFCC) and the polymer dispersion and latex sector (EPDLA). All relevant sectors including the tonnage distribution are shown in Table 2.
Table 2 Distribution of tonnage to sector associations for chain length C12, C14, C16
Sector association
|
Percentage of total tonnage
|
Tonnes per sector C12
|
Tonnes per sector C14
|
Tonnes per sector C16
|
AISE
|
32.26%
|
41,372
|
12,515
|
1,811
|
ATIEL
|
1.61%
|
2,069
|
536
|
91
|
CEPE
|
0.16%
|
207
|
125
|
9
|
ESVOC
|
0.16%
|
207
|
125
|
9
|
COSMETIC EUROPE
|
16.13%
|
20,686
|
8,939
|
906
|
ECPA
|
8.06%
|
10,343
|
1,788
|
453
|
EFCC
|
16.13%
|
20,686
|
8,939
|
906
|
EPDLA
|
16.13%
|
20,686
|
8,939
|
906
|
ETRMA
|
0.16%
|
207
|
72
|
9
|
FEICA
|
0.81%
|
1,034
|
447
|
45
|
TEGEWA
|
0.16%
|
207
|
179
|
91
|
FERTILIZER EUROPE
|
8.06%
|
10,343
|
1,788
|
453
|
PPRM
|
0.16%
|
207
|
89
|
9
|
Total
|
100%
|
128,253
|
44,482
|
5,696
|
For the tonnage distribution within the different sectors the approach sector tonnage = tonnage formulation steps = tonnage end uses (industrial, professional, consumer) was used. Within the end uses a further distribution was considered. It was estimated that 60 % of the sector tonnage will be consumed at the industrial scale, 30 % at the professional scale, and 10 % by consumers. For household/ cleaning and personal care application, an equal distribution factor was used. Professionals and consumers will mainly have access to these chemical products. For the personal care sector an industrial use is not applicable. In conclusion, the tonnage of this sector was split equally between the professional and consumer applications (Figure 1). A detailed overview is provided in the Supplemental Information.
U.S. Monitoring data
A US monitoring campaign was conducted in 2016 by McDonough et al. which collected grab effluent samples from 44 wastewater treatment plants (WWTPs) across the US to generate statistical distributions of effluent concentrations for various anionic surfactants, including AS. The mean concentrations for AS, AES, Linear alkylbenzene sulfonates (LAS) and Methylestersulfonate (MES) were 5.03 ± 4.5, 1.95 ± 0.7, 15.3 ± 19, and 0.35 ± 0.13 μg/L respectively. All data are publicly available (McDonough et al. 2016).
Extrapolation factor U.S./EU
For comparison to the U.S. monitoring data an U.S./EU extrapolation factor was established. This factor was used to adjust for demographic and possible technological differences between the U.S. and EU situations. This extrapolation factor was based on three key indicators: U.S.:EU per capita chemical use (AS), U.S.:EU per capita water use, and U.S.:EU WWTP efficiency ratio.
Consumption of Alkyl Sulphate in the U.S. (as established in the Waterborne Report) was equated with the manufactured tonnages in the EU (as established in the REACH consortium by a confidential survey among the EU manufacturers). To calculate an average U.S.:EU per capita chemical use ratio, the collected tonnages (U.S.: 96,000 t/a (IHS, 2016); EU: 178,431 t/a) were divided by the number of inhabitants. Assuming ~327 Million inhabitants (2018) for the U.S. (IMF, 2019) and ~512 Million inhabitants (2018) for the EU (Eurostat, 2018). In the U.S. each inhabitant uses on average 294 g AS per year (0.81 g/day), whereas in the EU, each inhabitant uses 348 g AS per year (0.95 g/day). Therefore, for the U.S.:EU per capita chemical use a ratio of 1:1.2 was established, i.e. an EU inhabitant uses 1.2 times more AS then an U.S. inhabitant.
Per capita water use in the U.S. were taken from the US EPA Clean Watersheds Needs Survey 2012 (USEPA, 2016). The survey included data from over 13,000 municipal WWTPs in the U.S. With the iSTREEM model (Waterborne, 2018) the water per capita use was calculated by dividing the facility flow by the population served. The discharge rate varied considerably between the different facilities. The median per capita use of 406 L//day, which was considered as the most representative, was used for the U.S.:EU comparison. The EUSES model considers as a standard input 200 L per capita per day. This amount is slightly higher than the estimated weighted European Union average of 186 L/capita/day (Waterborne, 2018) by using data for each member state. Nevertheless, the value of 200 L/capita/day was considered as reasonable for the U.S.:EU per capita ratio. 200 L per capita per day (EU) compared to 406 L per capita per day (U.S.) resulted in an U.S.:EU ratio of ~ 2:1. In other words, in Europe the WWTP effluents are 2 times more concentrated compared to the U.S..
In general, most of the existing WWTPs in the EU (88.7 %, Struijs, 2014) and the U.S. (86 % according to Kapo, 2015) use and rely on the activated sludge process for domestic waste water treatment, where microorganisms mineralize non-recalcitrant organic pollutants to water and carbon dioxide, or degrade/transform them to acceptable forms, like microbial biomass (EC, 2012, The World Bank, 2015; Milieu WRC RPA, 2013). For the EU and the U.S. an equivalent treatment efficiency was assumed (U.S.:EU =1).
Overall, U.S.:EU extrapolation factor of 1.2 (per capita AS consumption) x 2.0 (dilution in effluent) x 1.0 (WWTP efficiency) = 2.4 was estimated for the comparison. Thus, one would expect 2.4 times higher concentrations in the EU Clocaleffluent then reported by McDonough et al. (2016) for the U.S. effluents.
Modelling approach
Clocaleffluent concentration were calculated by specific environmental release categories (spERCs) from industry associations (use maps) whenever applicable. For applications with no spERCs, the default release factors for the environmental release categories (ERC) were used (ECHA, 2016).
EUSES was used for the modelling of the EU concentrations in the WWTP effluent (Clocaleffluent). Although under EU REACH only the individual annual production volumes per legal entity per manufacturer are uses as the basis for the environmental exposure and risk assessment, in this project the total combined production volume of AS (as such and as a component of AES) was used for EUSES modelling.
EUSES is the standard Tier I tool for exposure calculations of industrial chemicals. The tool forms the basis for all further exposure modelling tools developed within the context of EU REACH like ECETOC TRA, Chesar and EasyTRA (EasyTRA is a commercial software offered by Jansen-Systems, 42799 Leichlingen, Germany).
For the estimation of the AS Clocaleffluent concentration in the EU, the EasyTRA tool by Jansen Systems GmbH was used. In cooperation with Jansen-Systems GmbH an extension of the tool was developed to display the average Clocaleffluent concentrations directly.
The default EUSES daily discharge rate of 2000 m³/d for a municipal WWTP (200 L wastewater per capita for a population of 10,000 inhabitants) remains unchanged for the Clocaleffluent calculations (ECHA, 2016).
For each chain length (C12, C14, C16) a substance data set was generated in the tool. The environmental behaviour of the AS surfactants, the physico-chemical properties: molecular weight, vapour pressure, water solubility, partition coefficient and adsorption of the representative homologues AS C12, Na (CAS No. 151-21-3); AS C14, Na (CAS No. 1191-50-0) and C16, Na (CAS No. 1120-01-2) were taken into account (Table 3).
Table 3 Substance properties (taken from the REACH dossiers)
Physico chemical
properties
Homologues
|
Molecular weight
[g/mol]
|
Vapour pressure
[Pa]
|
Water solubility
[g/l]
|
Partition coefficient
[log Kow]
|
Adsorption coefficient
[log Koc]
|
AS C12, Na
CAS: 151-21-3
|
288.38
|
0.18
|
130
|
-2.03
|
2.5
|
AS C14, Na
CAS: 1191-50-0
|
316.43
|
<10
|
~ 100
|
2.19
|
3.13
|
AS C16, Na
CAS: 1120-01-0
|
344.49
|
<20
|
1.54
|
2.19
|
3.515
|
Further, substance-specific biodegradation rates were used in a second step, where appropriate, e.g. increased biodegradation rates (192 per day instead of the default of 24 per day for WWTP) to evaluate, if this higher tier approach leads to more realistic predictions.
So, for each C-chain a Clocaleffluent-value was obtained. In the end, the three Clocaleffluent-value were summed to yield an overall AS Clocaleffluent-value, which is than compared to the US monitoring result.’
The uses for the assessment were based on information by the sector associations use maps and were distributed amongst the sectors and the single uses as described in point ‘use pattern’. For industrial sites no further split was made to estimate the local site tonnage.
For the estimation of the local amount for widespread uses, the EUSES model already considers a default fraction of the main local source of 5.5E-7 year/day to break down the overall tonnage per application to the amount used at the local scale. This reduction factor includes the fraction of the “tonnage for the use” used in the region (0.1), the fraction of the regional tonnage (0.0005) used in the standard town (10,000 inhabitants) compared to the number of inhabitants in the region (20,000,000 inhabitants) and the number of days in a year (365 days). An additional default safety factor of 4 is applied by EUSES to cover temporary peaks. Based on the information from the specific environmental release categories (spERCs) for AISE and Cosmetics Europe a fraction of EU tonnage used in region of 0.04 (AISE) or 0.053 (Cosmetics Europe) and a fraction of the regional tonnage used locally of 0.00075 without a safety factor for seasonal peaks was used (Price et al., 2010).