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Function and use
Chemical products can also contain other substances with antimicrobial effects. These substances also help to improve the keeping qualities of the product and include function chemicals such as alcohols, essential oils, alkalis and acids.
Chemical products that can contain preservatives include washing-up detergents, cosmetics, cleaning agents, cutting fluids, and some oils and propellants.
A preservative may consist of one or several active substances, i.e. substances that have antimicrobial activity, as well as various kinds of additives. Preservatives can have various names, even though they contain the same active substances. An active substance may be identified by its chemical name, its cas-number or E-number.
The levels of active substances in preservatives vary from about 5 ppm (parts per million) to higher values. Normally, products contain preservatives at levels between 1% and 0,001%. (0,001% = 10 ppm).
Microorganisms grow readily in neutral or approximately neutral products (pH 5-8) containing a high proportion of water (> about 75%).
Almost without exception such products contain preservatives, though this is not always stated on the package or in the product information.
Generally, no preservatives are needed in the following types of products.
- Acid or alkaline products having pH<3 or pH>10.
- Products where the levels of surfactants exceed about 30%.
- Products containing combinations of surfactant and alcohol (ethanol or isopropanol) at sufficiently high levels.
However, it cannot be taken for granted that such products do not contain preservatives. It is not uncommon that raw materials for chemico-technical products contain preservatives, and these will of course therefore also be found in the finished product. Manufacturers themselves are not always aware that their raw materials contain preservatives. Preservatives that are not intentionally added to the product may also originate from the cleaning of production equipment such as mixing tanks.
Preservatives are not always specified in the product information. "Contains preservatives" is sometimes all that is stated. Preservatives in products can also be easily exchanged, and this occasionally takes place without the consumer being informed. Products produced for consumption during the summer may contain more or other preservatives than those intended for colder periods of the year.
Acetic acid, E 260, is used in products such as foods.
1,2-Benzisothiazoline-3-one (synonym: BIT, Proxel)
Benzoic acid, E 210, and its salts and esters can be found in products such as cosmetics and foods.
Benzyl alcohol can be found in cosmetics.
2-Benzyl-4-chlorophenol (synonym: chlorophene) can be found in products such as cosmetics.
1,3-Bis(hydroxymethyl)-5,5-dimethylimidazolidine-2,4-dione can be found in cosmetics.
5-Bromo-5-nitro-1,3-dioxane is sold under the trade name Bronidox. The substance can be found in cosmetics.
2-Bromo-2-nitropropane-1,3-diol can be abbreviated BNPD. It is commonly used in products under the trade names Bronopol-Boots, Myacide BT and Myacide AS. BNPD is used in pharmacological and hygiene preparations, as an antimicrobial agent in paints and cutting fluids, and for water treatment.
The manufacturer recommends levels of 0.01-0.1% in hygiene preparations. In products intended for children, levels of maximally 0.02% are recommended. The substance can be found in products with pH < 6 and normally at levels of 10-50 ppm.
BNPD is readily soluble in water and has low solubility in fatty substances. It is stable in acid solutions and becomes less stable with increasing pH-values. Breakdown products of BNPD include formaldehyde, bromide ions, nitrite ions, 2-hydroxymethyl-2-nitropropane-1,3-diol, 2-bromo-2-nitroethanol and tris(hydroxymethyl)nitromethane. In tests performed in alkaline solution (pH=9), BNPD was broken down to, among other substances, formalin in an amount corresponding to 10% of the BNPD-weight.
Calcium acetate, E 263, is used in products such as foods.
Calcium bisulphite, E 227 (synonym: calcium hydrogen sulphite), is used in products such as foods.
Calcium propionate, E 282, can be found in products such as foods cosmetics and foods.
Calcium sulphite, E 226, is used in products such as foods.
Chlorhexidine preparations contains, among other substances, 1,6-di-(4-chlorophenyldiguanido)-hexane. The substance is slightly soluble in water.
Chlorhexidine can be found in cosmetics, etc.
2-Chloroacetamide can be found in produccts such as cosmetics, adhesives, shoe polish and cutting fluids.
N-(3-Chloroallyl)-hexaminium chloride (synonyms: Quaternium 15, methenamine-3-chloroallyl chloride) can be found in cosmetics and in industrial, waterbase products.
p-Chloro-m-cresol can be found in cosmetics. The substance is sparingly soluble in water (4 g/l).
5-Chloro-2-methyl-4-isothiazoline-3-one is used together with 2-methyl-4-isothiazoline-3-one as an active component in products with trade names such as Kathon CG (1.5%), Kathon WT (15%), Kathon 886 MW (15%) and RH-886 T (56%). In addition to these substances, the products may include water at levels up to 75% and various kinds of salts in varying amounts.
An example is Kathon CG, which contains 1.5% active substance as specified above, 23% magnesium salts and 76.5% water. The substance is used as a preservative in cosmetics and hygiene products and is recommended by suppliers at levels up to 15 ppm in products that are intended to be rinsed off the skin, e.g. shampoo and soap. In products such as mascara, which remain on the skin for a prolonged period of time, recommended levels are 7,5 ppm. Levels of 10-15 ppm are normally used, but in paints levels may be about 30 ppm. Examples of raw materials that may contain Kathon CG are surfactants, polymers (polyacrylates, polycarboxylates) and waxes (wax emulsions).
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Acetic acid, E 260, that is stronger than 90% is classified as follows: inflammable; strongly corrosive; acts as an irritant in the respiratory passages. Acetic acid at concentrations in the range 25-90% is classified as corrosive and dangerous if swallowed. The substance is approved in Sweden as a preservative in food products.
1,2-Benzisothiazoline-3-one (synonym: BIT, Proxel) is classified as harmful in contact with skin and skin allergenic.
Benzoic acid, E 210, can be expected to act as an irritant on skin. Otherwise, it is said to have little effect on health.
The substance is approved in Sweden as a preservative in food products. It has been approved by the EU as a preservative in cosmetics at levels up to 0.5%. The salts and esters of benzoic acid have also been approved by the EU as preservatives in cosmetics.
Benzyl alcohol has been classified as follows: harmful by inhalation and if swallowed; acts as an irritant to skin and eyes.
The substance is approved by the EU as an ingredient in cosmetics at levels up to 1%.
2-Benzyl-4-chlorophenol (synonym: chlorophene) has shown medium-high acute toxicity in animal tests. The substance has been approved by the EU as an ingredient in cosmetics at levels up to 0.3%.
1,3-Bis(hydroxymethyl)-5,5-dimethylimidazolidine-2,4-dione - no information has been found on the impact of this substance on health. It is approved by the EU as an ingredient in cosmetics at levels up to 0.6%. Due to its chemical structure, the substance can be expected to release a certain amount of formaldehyde.
5-Bromo-5-nitro-1,3-dioxane is reported to be moderately allergenic on skin. The substance has been approved by the EU as a preservative in cosmetics of "rinse-off" type at levels of up to 0.1%. The EU warns of formation of nitrosamines if the substance is used in products containing amines.
2-Bromo-2-nitropropane-1,3-diol (synonym: BNPD) should be classified as harmful on the basis of data from animal tests. BNPD is described as having a moderate capacity for inducing skin allergies. The substance is said to be a strong eye irritant and to be capable of causing difficulties in breathing and stomach injury. It can contain such large amounts of the breakdown product formaldehyde as to induce eczematous reactions in persons who are already sensitized. For more detailed information, see "Formaldehyde".
Nitrite is another breakdown product that can be present in BNPD. In conjunction with amines or amides nitrite can form nitrosamines, which are suspected of being carcinogenic. BNPD should therefore not be used in products that contain diethanolamine, triethanolamine, lauryldiethanolamide or other diethanolamines. The main risk in this connection is the formation of nitrosamines. If instead a compound such as monoethanolamine is used in the product, this compound should be investigated and tested as regards possible impurities in the form of diethanolamine.
Bronopol, which to a large extent consists of BNPD, is approved by the EU as a preservative in cosmetics at levels up to 0.1%. The EU warns of the formation of nitrosamines.
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1,2-Benzisothiazoline-3-one (synonym: BIT) - no information has been found.
Benzoic acid, E 210, is readily degradable in aqueous environments.
Benzyl alcohol is readily degradable in aqueous environments. The substance seems to have low toxicity to algae but may be toxic to fish.
2-Benzyl-4-chlorophenol (synonym: chlorophene) - no information has been found. The substance is a chlorophenol, i.e. it belongs to a group of substances which the Swedish Water and Waste Water Works' Association considers to be untreatable. According to their directives, these substances should not be present in wastewater.
1,3-Bis(hydroxymethyl)-5,5-dimethylimidazolidine-2,4-dione - no information has been found.
5-Bromo-5-nitro-1,3-dioxane - no information has been found.
2-Bromo-2-nitropropane-1,3-diol (synonym BNPD) is toxic to crustaceans (Daphnia), among other organisms. As it almost warrants classification as very toxic, it is considered an environmentally hazardous substance. It is very soluble in water but is not expected to spread or accumulate in the natural environment because it is rapidly degraded.
Calcium acetate, E 263, probably does not cause any problems in the environment, since the acetate component (acetic acid) is readily degradable and calcium is not environmentally hazardous.
Calcium bisulphite, E 227, may cause environmental problems because sulphur dioxide can be formed and given off. Sulphur dioxide can then be oxidized to sulphuric acid and contribute to acidification.
Calcium propionate, E 282, is probably readily degradable because propionic acid is readily degradable.
Calcium sulphite, E 226, may cause environmental problems because sulphur dioxide can be formed and given off. Sulphur dioxide can then be oxidized to sulphuric acid and contribute to acidification.
Chlorhexidine is reported to be very toxic to fish and toxic to aquatic organisms such as Daphnia. Furthermore, the substance is said to have a tendency to bioaccumulate. It should therefore be considered to be environmentally hazardous.
2-Chloroacetamide - no data have been found. The substance can be hydrolysed to chloroacetic acid, which is toxic to most living organisms.
N-(3-Chloroallyl)-hexaminium chloride (synonym: Quaternium 15, metheneamine-3-chloroallyl chloride) is probably not readily degradable, because it is a derivative of hexamethylenetetramine, which is not readily degradable.
p-Chloro-m-cresol - some data indicate that the substance is very toxic to fish and that it may bioaccumulate and is resistant to degradation. It is probably environmentally hazardous.
p-Chloro-m-cresol is a chlorophenol, i.e. it belongs to a group of substances which the Swedish Water and Waste Water Works' Association considers to be untreatable. Under their directives, these substances should not be present in wastewater.
5-Chloro-2-methyl-4-isothiazoline-3-one and 2-methylisothiazoline-3-one are the active components of Kathon CG, among other products. These active components are very toxic to fish and crustaceans (Daphnia). Substances that are very toxic are classified as environmentally hazardous. Since Kathon CG contains more than 1% of the active component, it is also environmentally hazardous.
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If the product contains preservatives, the substance in question should be identified by means of its chemical name, cas-number and/or E-number. If a chemical identification cannot be made, it is impossible to know what risks may be associated with the substance.
Also check the possible content of preservatives in raw materials such as surfactants, polymers, thickeners, acrylate polymers and waxes.
Substances for which health and the environmental information is lacking should be avoided.
The following preservatives are considered to cause only minor problems as regards health and the environment when used in chemico-technical products and can therefore be accepted:
p-Hydroxybenzoic acid esters (parabens)
The following preservatives are considered to cause considerable problems as regards health and/or the environment when used in chemico-technical products and cannot, therefore, be accepted:
1,2-Benzisothiazoline-3-one (synonym: BIT)
Bronidox, see 5-bromo-5-nitro-1,3-dioxane
Bronopol, see 2-bromo-2-nitropropane-1,3-diol
N-(3-Chloroallyl)-hexaminium chloride (synonym: Quaternium 15)
1-(4-Chlorophenoxy)-1-(imidazol-1-yl)-3,3-dimethyl butane- 2-one
1,2-Dibromo-2,4-dicyanobutane (synonym: DBDCB)
3,3'-Dibromo-4,4'-hexamethylenedioxydibenzamidine (synonym: dibromohexamidine)
5,5'-Dichloro-2,2'-dihydroxydiphenyl methane (Dichlorophene)
Euxyl K400, see 1,2-dibromo-2,4-dicyanobutane
Kathon CG and others, see 5-chloro-2-methyl-4-isothiazoline-3-one
1,3,5-Triazine-1,3,5-(2H, 4H, 6H)-triethanol
Trichlocarban (synonym: 3,4,4'-trichlorocarbanilide)