Results

Overall, 76 documents were initially retrieved and reviewed. Of these, 38 were selected for further review based on SS/NTS relevance and data availability/transparency. Identified chemicals and associated information was extracted from each of these studies. Of the final selected studies, 26 directly screened the product, 8 screened for chemical migrants from products, and 4 studies did both. Over half the studies were published within the last 2 years which further indicates that the application of NTS/SS in product and material analysis is a relatively recent but fast-growing field.

Only 34 out of the 38 studies contained chemicals identified at high confidence level, i.e. Schymanski level 1 or 2. Of these, 19 used NTS, 11 SS, and 4 employed both methods. In total, more than 1,500 products were screened covering different product categories such as plastics, elastomers, chemical products/­material related, paper/­paperboard, textiles and wood. By far most studies looked at plastic products (>900 products), while the second biggest product category was textiles (>200 products). Although we believe that this is a relevant trend, the literature search was biased due to search terms and time constraints. As seen in Table 2, about 4–8 studies were found for each product category with screening data of high reliability (Schymanski level < 3) with the exception of the plastic material category where 20 studies were found. Many studies screened a broad range of products and therefore contributed with data to multiple product/material categories.

In total, nearly 3,000 unique chemical entries were registered at varying confidence levels from which approximately 1,700 were identified at Schymanski level 1 and 2 (Appendix, spreadsheet “C”). Of the latter, 28 substances are restricted under REACH, 4 are regulated as POPs with an additional 6 being proposed as POPs. Approximately 200 of the high confidence substances have a harmonized classification (CLH) under the CLP while 50 are included in the SVHC Candidate List. Finally, 61 of the identified chemicals have been prioritized as PMT/vPvM substances. Detailed hazard and regulatory information can be found in the Appendix, spreadsheet “D”.

The number of unique compounds detected and identified with high confidence in each product category can be seen in Table 2. The highest number (1,014) of unique compounds were detected and identified in the “plastic” material category, and even more compounds were further detected in the mixed product categories, “plastic +/or elastomers ” and “plastic + wood”. Four hundred unique compounds were identifed in the “other” products category. These categories are very broad and included a range of different products with varying applications. This might partly explain why more compounds were identifed in the “plastic” and “other” material categories in comparison to the material categories “textile”, “paper/ paperboard” and “elastomers” which included a narrower range of products and applications. For example, the product category “elastomer” included products such as recycled tire products, erasers and crumb rubber, whereas the product category “plastic” included products such as tableware, recycled plastic pellets, water bottles, food contact materials, toys, childrens products, PVC flooring, auto products, plastic electrical waste, single use items, shower curtains and vinyl upholstery. The “other” product category included mostly personal care products, cosmetics, paint and cleaning products.

Table 2 Numbers of unique Sl 1 & 2 compounds and studies per material category.

The most frequently detected chemicals at high confidence are presented in Table 3 (see also in Appendix, spreadsheet “C”). These include two widely used phthalate plasticizers that are also ubiquitous environmental pollutants, diethyl phthalate and dibutyl phthalate. Dibutyl phthalate is a known endocrine disruptor and reproductive toxicant and its use is restricted under REACH, while diethyl phthalate is under assessment for endocrine disruption. Benzophenone, a chemical classified as a carcinogen with a wide variety of registered uses for instance in air care/fragrance products, polishes and waxes, personal care products, washing & cleaning products, etc. but also commonly used as a UV stabilizer added to plastic and textile products is also among the most frequently detected. Palmitic acid, a saturated carboxylic acid with 16 carbons in the carbon chain, is the most widely distributed and abundant fatty acid. It has numerous industrial and consumer applications; amongst other things it is commercially used to make lotions. The compound [2,2,4-trimethyl-3-(2-methylpropanoyloxy)pentyl] 2-methylpropanoate is more commonly known as TXIB and is an additive, for instance in PVC, but also in many other consumer products such as adhesives and sealants, cosmetics and personal care products. Tetra-, hexa-, hepta-, octadecane and heptacosane are all saturated linear alkanes, which may be found in fuels or paraffin waxes. With the exception of heptadecane, octadecane and heptacosane all the most frequently detected substances are high production volume chemicals.

Table 3 Overall most frequently detected chemicals identified with high confidence levels (Schymanski level 1 and 2) and related regulatory and hazard information.

The most frequently detected compounds (Schymanski level 1 & 2) using GC and LC are presented in Tables 4 and 5 (see also in Appendix, spreadsheet “C”). Compounds frequently detected with GC were mainly aliphatic hydrocarbons and plasticizers, whereas compounds frequently detected with LC techniques mainly included adhesives, copolymers and monomer components, many of which are industrial products and do not have CAS numbers. GC and LC are considered complementary techniques as the methods are applicable to substances of different chemical and physical properties. From the gathered results it was observed that both chromatographic techniques were combined with SS and NTS analysis to the same extent; however, GC techniques were more commonly used in the literature, which resulted in more than twice as many uniquely identifed compounds being detectd with GC techniques compared with LC. The use of these techniques depend on the material category being screened but also on the substances of interest. It was found that GC techniques were the primary chromatographic method used in the detection of compounds in chemical products/ material related, elastomers and textiles while LC techniques were the primary chromatographic method used in the detection of compounds in paper, paperboard and wood. Both GC and LC techniques were used in studies for SS and NTS of plastic although GC was more frequently used. Of the approximately 1700 unique substances identified with high confidence in the different product material categories, 900 (56%) were detected with GC techniques, 600 (38%) with LC techniques and 100 (6%) with both techniques. The reason for the more frequent usage of GC techniques is thought to be due to GC-MS being a more established and standardized technique where large spectral databases such as NIST facilitate and simplify the identification of compounds. This enables for a high confidence level when screening with GC-MS, making it easy to identify peaks with Schymanski level 2b. Advances in ionization techniques and in mass spectrometers have enabled screening to be performed with LC as well where a broad range of compounds can be analyzed and detected. Major challenges with LC screening are that the tehcniqe is not stadardized, spectral databases cover a limited range and high noise levels from interfearing making identification with sufficient reliability more difficult to achieve.

Table 4 Most frequently detected compounds using GC-MS. Chemical names in bold are among the 10 most frequently detected chemicals overall (Table 2)

* Substance CLH classified as Acute Tox. 4, STOT SE 3, Skin Irrit. 2, and Eye Irrit. 2

Table 5 Most frequently detected compounds using LC-MS

The most frequently detected compounds in each PRIO category are presented in Table 6 (see also in Appendix, spreadsheet “C”). For the compounds most frequently found in the category ‘Chemical product/material related’ there were four that can be considered as fuel components, for instance the reproductive toxicant and REACH restricted toluene, 1,3-dimethylbenzene (m-xylene), ethylbenzene and the classified carcinogen cumene. Ethyl butyrate is an ether that is used as a fragrance or fragrance additive, but has also been proposed as a green solvent. Three coloring agents are among the most frequently detected i.e., Disperse Red 354, Red 73 and Blue 291G with the latter identified as a PM substance as well as a plastic monomer classified as carcinogen, styrene, and phenylmethanol (benzylalcohol) which according to ECHA has wide spread use in consumer products.

Table 6 Most frequently detected chemicals per PRIO category. Chemical names in bold are among the 10 most frequently detected chemicals overall (Table 2)

The groups elastomer, paper/paperboard, plastic, and plastic + wood and plastic +/or elastomer all have limited, and quite similar chemicals that are found most frequently. Many compounds are long chain aliphatic hydrocarbons/acids such as tetradecane, hexadecane, heptadecane, octadecane and palmitic (hexadecanoic) acid. For the plastic, plastic +/or elastomer there are also antioxidants, some process chemicals and plasticizers while the elastomer group was dominated by long chain aliphatic hydrocarbons along with a couple of antioxidants such as diphenylamine which is classified as aquatic toxicant and a PMT substance and butylated hydroxytoluene, a potential endocrine disruptor. For the plastic category, benzophenone, diethyl phthalate, dibutyl phthalate along with another restricted phthalate plasticizer, bis(2-ethylhexyl) phthalate are dominant. Tetrahydrofurfuryl alcohol, a reproductive toxic substance that is used as an industrial solvent, a phosphate ether antioxidant, AT-168, and the common additive known as TXIB (2,2,4-trimethyl-1,3-pentanediol diisobutyrate) were also among the most frequently detected. There was also a compound that is used in the production of antioxidants and UV-stabilizers, 2,4-di-tert-butylphenol, which may be present due to degradation of other compounds in the material.

In the plastic + wood category all the frequently detected compounds are long chain aliphatic hydrocarbons exept for the plasticizer diethyl phthalate. The long chain aliphatic compounds also dominate the category of paper/paperboard with the addition of benzophenone and dibutyl phthalate replacing diethyl phthalate. For the category of plastic +/or elastomer another phthalate plasticizer bis(2-ethylhexyl) benzene-1,4-dicarboxylate was frequently detected, along with eurcamide, a chemical commonly used in plastic processing as a slip additive. A surfactant known with the commercial name Surfynol or Surfadol, 2,4,7,9-tetramethyl-5-decyn-4,7-diol (a prioritized PM substance), was also frequently detected. N-phenyl-4-(2,4,4-trimethylpentan-2-yl)aniline, an antioxidant structurally similar to 6PPD and triphenyl phosphate a substance used for is flame retarding and plasticizing properties appeared in the list. Triphenyl phosphate was recently added to the SVHC Candidate List due to its endocrine disruption potential. Interestingly, only two ultra short chain PFAS compounds (both classified as vPvM) are detected frequently in the category paper/paperboard + wood, trifluoromethanesulfonic acid and trifluoroacetic acid.

The textiles category is dominated by color agents, with different dispersive red dyes being most frequently detected, Disperse Red 354, 343, 311, 153 and 74. Other frequently detected compounds are benzophenone, two long chain aliphatic hydrocarbons, dibutyl phthalate and the solvent ethanol. In the last category listed, “other”, there is an antioxidant, butylated hydroxytoluene, three long chain aliphatic acids, palmitic acid, octadecanoic acid and oleic acid (an unsaturated octadecanoic acid) as well as a couple of aliphatic alcohols, 1-hexadecanol and 1-dodecanol. Bisphenol A ethoxylate methacrylate (BisEMA-2), which was most frequently identified, is possibly a plastic monomer used together with i.e. bisphenylglycidyl dimethacrylate (BisGMA) in dental composites. One fragrance compound was also identified, cyclopentaneacetic acid, 3-oxo- 2-pentyl-, methyl ester, which is also known as methyl dihydrojasmonate or hedione.

The frequency of detection of alifatic hydrocarbons and plastic or polymer-related compounds such as plastisizers, and antioxidants across several categories may indicate that the categorys themselves may be overlapping in the materials present or that similar additives are used in the different groups. There can also be a bias of which compounds are extracted to a high degree in the extraction methods used and determined with good recovery across the analytical method. It is also possible that a bias pertaining to the analytical method exists as well, with the aliphatic hydrocarbons, acids and alcohols being well suited for GC-MS analysis.