Summary and conclusions

Survey and Health Assessment of Possible Health Hazardous Compounds in Proofing Sprays

Many different types of proofing sprays are sold directly to the consumers as agents for aftertreatment of different types of textiles especially in order to obtain a water- and dirt-repellant effect.

In recent years, it has been observed internationally and in Denmark that spray products for proofing of textiles in certain cases result in acute respiratory illness and similar acute poisoning symptoms. During the period from 1991 to 2007, 84 cases of varying degrees of poisoning in connection with the use of textile proofing were identified in Denmark. It has not been possible to find any unambiguous reason for the cases of poisoning on the basis of the information about the compounds.

Therefore, this project has been implemented in order to investigate textile proofing sprays on the Danish market.

The starting point of the project was a need for greater knowlege about the compounds in this type of product and the size of the aerosols humans are exposed to.

The following elements form part of the project:

Literature retrieval and information search
Survey of products on the market
Investigation of chemical composition of substances
Investigation of liberation of small aerosols during use
Health assessment of the products.

The most important project results will be exmined in the following.

Literature and information search

By means of systematic searches in scientific data bases information has been collected about toxic effects in connection with spray proofing and about the composition of the proofing sprays with regard to proofing agent, solvent and possible propellant.

Many of the cases of poisoning that have been reported for proofing sprays have in common that a previous rewording has taken place of the products in connection with substitution of the solvents used.

Some proofing sprays that have caused acute toxicity in humans have subsequently been tested on animals. No information exists about the toxicological impact mechanism of particular proofing sprays but is must be assumed that the proofing agents influence the surface conditions in the lungs e.g. the surface tension and thus the lung function and might hamper the passage of oxygene across the alveolars.

The spray proofing agents involved in the reported cases of toxification most often contain some type of fluorcarbon polymer (15 out of 17 products). The manufacturers keep the chemical structure secret to avoid product copying. Please note that a few products in addition to fluorine compounds also contain silicone compounds.

In general, it is easier to procure information about which solvents and propellants form part of the product, whereas amount specifications rarely are stated.

Only limited information exists about the size distribution of the aerosols consumers are exposed to when using proofing spray. This project uses the term aerosols about material and substances that are not gaseous and that are suspended in air. As a starting point, liquid aerosols are in question but it cannot be ruled out that these subsequently will assume a solid or amorphous physical structure.^[1]

The type of the solvent as well as the appearance of specific fluorcarbon compounds and the aerosol size can be of importance to the observed cases of poisoning but a more precise reason cannot be concluded from literature.

Survey

The survey comprised the following activities:

Contact to the retail trade. 21 of the procured products were purchased in physical shops.
Search on the internet. Many homepages with internet shops were visited and 5 of the products were purchased on the internet.
Contact to distributors/importers. Approaching importers of the products that form part of the survey resulted in information about the substances in the products whereas information on sale of the products in Denmark only has been received from few importers.

Products have been purchased for textile proofing within the product groups:

Products for proofing of shoes
Products for proofing of tents and the like
Products for proofing of furniture
Products for proofing of clothes for outdoor use, e.g. jackets or the like.

The main selection criteria for purchase of products have been that the products have to be sold to a certain degree. It has especially been possible to use that criterion when visiting physical shops and the staff was asked which products are “best selling”, but it has not been possible to use that criterion in connection with internet trade.

Consumption of sprays for textile proofing

It has not been possible to procure information from any of the contacted importers about their sale on the Danish market and therefore it has not been possible to estimate the extent of products sold for textile proofing.

Selection of products for further investigation

The survey resulted in the registration of 29 products (17 spray products with propellant and 12 spray products with pump) and in co-operation with the Danish Environmental Protection Agency 16 products were selected for further investigation.

Chemical analyses

16 products were chosen for analysis and the principle was that spray as well as pump products should be represented, that fluorine as well as silicone based products should be investigated and that products with known as well as unkown substances should be examined.

Subsequently, the following screening analyses were carried out:

Element analyses for content of fluorine or silicone in the surface coating of proofed textile by x-ray.
Screening for content of volatile and semi-volatile organic substances in the aerosol mist that appears when the products are used, by means of gas chromatography with mass spectrometric detection (GC/MS).

The screening analyses showed that nearly all products contained varied amounts of fluorine (0.1-15 %). Fluorine was not detected in 2 out of the 16 analysed products. Silicium was measured in 11 products.

Summarised, the results show that 13 of the 16 products probably are based on a fluorcarbon coating. One single sample contained only a small amount of fluorine and substantially more silicium.

The screening analyses for volatile and semi-volatile organic substances showed content of a wide range of solvents and propellants. However, in two products it was not possible to demonstrate content of volatile or semi-volatile organic substances. 10 of the 14 other products contained large amounts of hydrocarbons in the form of hydrocarbon mixtures that function as organic solvents. Most products contained varying amounts of polar organic solvents. Some products also contained aromatic compounds and one single product contained chlorinated solvents.

In addition, the screening analyses showed the appearance of one fluorine compound and silicone/siloxane compounds. From the chemical analyses, the assumed fluorine substances turned out to be structurally related to the so-called fluortelomers, meaning substances with the structure CF₃(CF₂)_nCH₂CH₂OH. An example is 1H,1H,2H,2H-perfluoroctanol.

In the light of the screening analyses, 10 products were chosen for quantitative chemical analyses. The quantitative analyses were carried out on 14 substances in the chosen products. For some products, the concentration in the products was below the detection limit but most substances could be analysed in one or several products.

When comparing with an analysis of a standard it could be ruled out that some of the products contained 1H,1H,2H,2H perfluoroctanol. Additional analyses could not uncover the exact chemical structure of the detected fluorine compounds. The concentrations of detected fluorine compounds were low compared with the x-ray analyses and therefore it must be assumed that the main part of the fluorine compounds is polymerised during the analysis and therefore they cannot be detected. That might be because the active ingredient is designed to polymerise on contact with air and in that way create a proofing coating.

Aerosol analyses

All 16 products that were chosen for analyses were analysed for liberation of small aerosols in the size interval of 6-650 nm. As far as it is known, it is the first time systematic measurements were carried out on small aerosols and nanoaerosols which the consumer is exposed to when using spray proofing.

The results unambiguously show that middle-sized aerosols in the interval of 50-200 nm are liberated when propellant based spray products are used. The measured aerosol concentrations are in the area of 10⁵-10⁶ cm^-3 at an exposure time of 10 s. When using pump products the amount of liberated small aerosols is very small or insignificant.

The reason for the difference between pump products and propellants is that pump products give larger primary aerosols that are deposited more efficiently on the textile surface than the smaller aerosols from propellants. In the case of non-deposited aerosols a quick evaporation of solvents will take place and then aerosols consisting of non-volotile substances will remian in the air.

As part of the project, a test rig was developed for investigation of proofing products with regard to liberation of small aerosols and determination of the aerosol size distribution.

Health assessment

In the project, health assessments were carried out on 6 substances found either in the semi-quantitative screenings or the quantitative analyses of chemical substances in spray products intended for textile proofing. The assessments of the health conditions were carried out on the basis of worst worst case scenarios. The 6 investigated substances were cyclohexane, butan-2-on, 1-Butanol and butyl acetate which are solvents and perfluoroctan-1-ol and dodecamethylpentasiloxane.

The assessments showed that the procured textile sprays only contained substances that were listed in the Danish Ministry of the Environment’s Regulation on propellants and solvents to be used in aerosol products (the Danish Environmental Protection Agency, 1984). However, the organic solvent butyl acetate must not appear in products for indoor household use. The content of organic solvents is not a health related problem in these spray products assessed in relation to substance limit values of the Danish Working Environment Authority.

In connection with the assessed substances the rule is that margin of safety (MOS) has to be at least 100 compared to the NOAEL value (no observed adverse effect level) in the critical effect in a relevant animal study. A factor 10 is used for extrapolation from animals to humans and an additional factor 10 is used to protect the particularly sensitive groups or individuals. That criterion is normally used to protect users of consumer products.

On the basis of that criterion, the content of a polydimethyl siloxane that was found in one single spray product will not be a health hazardous risk.

Substances that structurally are similar to 1H,1H,2H,2H-perfluoroctanol were estimated to have MOS values of approx. 10, that is 1/10 of the protection level that normally is used for consumer products. In addition, it has only been possible to account for a small part of the total amount of fluorine compounds in the products and it is only that small part that forms part of the health assessment. This type of substance gives another reason for cautiousness as the available literature shows that fluorine compounds exist in most of the cases of poisoning where information about the chemical composition is available.

Aerosols from proofing products consist of small drops of proofing agent dissolved in solvents. The proofing agents are solid or liquid with extremely low vapour pressure. The solvents have a rather high vapour pressure and will evaporate quickly and leave liquid or solid particles of the proofing substances floating in the air – the smaller the aerosol particles the quicker the evaporation. In practice, the aerosols that are inhaled mainly consist of heavy volatile proofing substances. In concentrated form that can influence the surface tension in the lungs and result in changed lung function. No information exists about the combined influence of solvent vapours and aerosols on the respiratory system (possibly with a small solvent content).

Conclusion

Most ascertained cases of poisoning that arise when textile proofing has been used involve products that are based on fluorcarbon compounds.

It has not been possible to determine the exact chemical structure of the fluorcarbon compounds that exist in textile proofing agents and therefore it has not been possible to carry out a final health assessment of the products. However, in the light of the project results that prove the appearance of fluorine in most products it must be assessed as possible that exposure to non-polymerised or partly polymerised fluorcarbon compounds in rather high concentrations is possible.

The use of textile proofing agents sprayed with propellant results in a considerable exposure to fine (< 1 µm) and ultra fine aerosols (nanoaerosols) (< 100 nm). The toxicological effect from inhaling nanoaerosols is not yet known. Existing information in the field cannot document that small aerosols in themselves are harmful. However, many international research activities are being carried out on the toxicology of nanoaerosols and in a couple of years they will hopefully be able to shed more light on this problem. Aerosols can be carriers of (re)active chemical substances, e.g. fluorcarbon monomers but the importance is not known as the chemical structure of the substances could not be detected or procured in this project.

The classic toxicological assessments of the individual substances in a product are apparently insufficient when the product is sprayed by means of propellant. Physical properties, e.g. aerosol size, are determining factors that show if and which toxic effect might arise in the respiratory system. Toxic effects can arise when the solvents in aerosols evaporate after inhalation and result in a high local concentration in lungs/alveolars. When the solvent is evaporated small, solid or liquid aerosols are created. Respiratory symptoms could also be due to possible depositing of insoluble substances, e.g. fluorcarbon compounds on the surfaces of the respiratory passages. In that way, the proofing substances can affect the surface conditions in the lungs and thus the lung function and possibly restrain the passage of oxygen across the alveolars.

Footnotes

^[1] In literature, the terms aerosol and particle are often used without an unambiguous definition of the difference between the terms. In some cases, aerosol is used as term for liquid materials and particle as term for solid materials.