The primary focus of Nature’s Pulchritude is to educate. This post is the third in a series of in depth posts that will educate you about the various preservatives in hair and skin products, as well as their potential toxicity.
Preservatives are added to cosmetics, personal care products, and food to maintain a products integrity and stability by inhibiting or reducing the growth of microorganisms such as bacteria and fungus (FDA). Most products sold via retail sit for extended periods of time during shipping, in a warehouse, and on store shelfs that allow enough time for a product to spoil or cause microbial growth which render the product unfit for use. This is particularly true for products that contain water, such as many conditioners and moisturizers, and other active ingredients (antioxidants and emulsifiers) that would otherwise lose their effectiveness and stability over time.
Preservatives are chosen in cosmetics based on a variety of factors which include ability to inhibit growth over a broad spectrum and method of derivation (natural vs. synthetic). Preservatives tend to be in concentrations less than 2% of the weight of the formula, however, widespread use of potentially harmful preservatives, such as parabens, has been a great cause of concern for some scientists and consumers. The Food, Drug, and Cosmetic Act does not grant the Food & Drug Administration the authority to regulate the use of preservatives unless it is known to be “poisonous or deleterious” (FDA).
Sodium Benzoate is a common preservative in many products that market themselves as being ‘natural’ or ‘organic.’ Sodium Benzoate is a sodium salt of benzoic acid, which is naturally occurring in apples, cranberries, plums, ripe cloves, and cinnamon in low levels, and is often produced synthetically by reacting Benzoic Acid with Sodium Hydroxide (NaOH). Sodium Benzoate (NaC7H5O2) is used as a food, medicine, and cosmetic preservative as a bacteriostatic and fungistatic, both of which reduce or limit the growth or bacteria or fungi by interacting with protein production, metabolism and DNA replication, without otherwise harming the bacteria or fungi. Its use is limited as a preservative by the FDA to 0.1% of a formula by weight. Sodium Benzoate is generally regarded as safe by the FDA, however, when combined with ingredients such as Vitamin C or E it can react to form benzene, a known carcinogen.
Sodium Benzoate was found to be present in 34% of 204 tested products (92 shampoos, 61 conditioners, 34 liquid soaps, and 17 wet tissues) (Yazar et al. 2010). Though the FDA limits the use of sodium benzoate to 0.1% by weight in food, it is limited to 2.5% in rinse off products and 0.5% in leave on products by the European Union Cosmetic Directive (Yazar et al. 2010). Though Sodium Benzoate is generally considered safe, it can become a serious hazard if it is combined with Vitamin C (ascorbic acid) or Vitamin E (tocopherols) as they react to form benzene (C6H6), a cancer causing hydrocarbon. The amount of benzene produced from these reactions was determined to be below dangerous levels (5 parts per billion) for consumption by the World Health Organization, based on presence of benzene in soft drinks. Benzene is classified as an A1 carcinogen (confirmed for humans) by the American Conference of Governmental Industrial Hygienists (ACGIH) and Group 1 carcinogen by the International Agency for Research on Cancer (IARC). Benzene is also a possible mutagen and developmental toxin in humans that is specifically toxic to blood, bone marrow, and the central nervous system, and may target the liver and urinary system. Limited studies show that after dermal (skin) exposure, benzene was metabolized by the liver and excreted. There is no available research on the formation and concentration of benzene in cosmetic products at this time, so it is best to avoid products containing sodium benzoate in conjunction with ascorbic acid (Vitamin A) or tocopherol (Vitamin E).
Sodium Benzoate appears to be a safer alternative to some commonly used preservatives on the market. Despite being a synthetic chemical used in ‘natural’ and ‘organic’ products, it serves its purpose as a preservative without exposing consumers to negative impacts under ideal conditions. It is not known as an allergen or sensitizer, nor is it itself toxic in the concentrations used in food and cosmetics. The largest concern with this chemical is its reaction with Vitamin C and Vitamin E to form carcinogenic benzene. Otherwise, it appears safe in cosmetics.
Yazar, K., Johnsson, S., Lind, M., Boman, A., and C. Liden. 2010. “Preservatives and fragrance in selected consumer-available cosmetics and detergents.” Contact Dermatitis. 64: 265-272.
Do any of your products or foods contain Sodium Benzoate? Do they also contain Vitamin C or E?