488 Journal of Health Science, 54(4) 488–492 (2008) The Release of Formaldehyde INTRODUCTION upon Decomposition of Antibacterial preservatives are widely used in 2-Bromo-2-nitropropan-1,3-diol cosmetics to prevent spoilage due to microbial (Bronopol) contamination. Several of these preservatives are known as formaldehyde (FA)-releasing com- pounds1–4) that release FA through decomposi- ∗ Keiji Kajimura, Takaomi Tagami, tion or degradation. 2-Bromo-2-nitropropan-1,3- Takeo Yamamoto, and Shozo Iwagami diol (bronopol: BP), one such substance, is ac- tive against a broad spectrum of bacteria, including Osaka Prefectural Institute of Public Health, 1–3–69 Gram-negative species that are resistant to many an- Nakamichi, Higashinari-ku, Osaka 537–0025, Japan tibacterial agents.5–7) In Japan, BP cannot be used (Received April 22, 2008; Accepted May 14, 2008; in cosmetics; however, in the U.S.A. and many Published online May 26, 2008) Western countries, this application is approved by law.8) We investigated the release of formaldehyde (FA) In recent years, with the rapid development of upon the decomposition of 2-bromo-2-nitropropan- information systems such as the World Wide Web, it 1,3-diol (Bronopol: BP), an FA-releasing substance has become easy to purchase cosmetics from over- widely used as an antimicrobial preservative in cos- seas. In addition, Japanese traveling abroad have metics and toiletries in many Western countries. The begun buying large amounts of cosmetics in other decomposition process producing FA mainly depends countries.9) BP, an FA-releasing substance, may be on temperature and pH. Notably, the pH of the BP- in these cosmetics. Special consideration is neces- diluted buffer solution was the factor most influenc- sary about the safety of cosmetics, because they are ing the release of FA. The release was markedly in used nearly constantly, and directly in contact with higher alkaline buffer compared with acidic buffer. the skin. FA, the simplest aldehyde compound, is When a BP solution [0.1% (w/v)] prepared with a a causative agent of sick building syndrome,10, 11) weakly alkaline buffer (pH 8.0) was stored at 25◦C, and a major public health concern. Many cases of the concentration of FA reached 30 ppm after 24 hr. systemic (e.g. anaphylaxis), and more often, lo- On the other hand, under acidic conditions (pH 2.0), calized (e.g. contact dermatitis) allergic reactions little FA was produced over 50 days. Homemade cos- are attributed to FA.12–14) In addition, The Inter- metics (lotions and jells) were made [with 0.1% (w/v) national Agency for Research on Cancer (IARC, BP] and stored at a constant temperature of 25◦Cfor 2004) has classified FA in group 1 (carcinogenic to 30 days. The concentration of FA increased with time, humans),15) based on limited evidence in humans, reaching 20 ppm after 50 days. We investigated sea- although the mechanism by which it induces tumors sonal variation in the release of FA upon decompo- is not fully understood. sition of BP in Osaka. BP test solution [0.1% (w/v)] There have been some studies on the stability was prepared with 0.005 M sodium phosphate buffer of BP in various conditions,16, 17) but very little has (pH 6.0) and stored at ambient temperature for 30 been reported about the release of FA upon its de- days. The experiment was conducted three times in composition. In the present study, we examined the different seasons (mid winter, early spring, and early effects of pH and temperature on the release of FA summer). It was found that the release of FA with upon decomposition of BP. decomposition of BP differed among the seasons. Key words ——2-bromo-2-nitropropan-1,3-diol, form- MATERIALS AND METHODS aldehyde, release, hydrogen ion concentration, tempera- ture Preparation of Buffer Solutions —— A 0.005 M sodium dihydrogen phosphate solution was pre- ∗To whom correspondence should be addressed: Osaka pared, and the pH adjusted to 2.0, 4.0, 6.0, and 8.0 Prefectural Institute of Public Health, 1–3–69 Nakamichi, with orthophosphoric acid or 0.005 M disodium hy- Higashinari-ku, Osaka 537–0025, Japan. Tel.: +81-6-6972- drogen phosphate solution. 1321; Fax:+81-6-6972-2393; E-mail: [email protected]. Preparation of Bronopol Test Solutions —— BP osaka.jp (Tokyo Chemical Industry Co. Ltd., Tokyo, Japan) No. 4 489 was diluted with the test buffer solution described of orange essential oil were dissolved in 450 ml of above [0.1–0.01% (w/v)], and separated (25 ml) in distilled water.22) The gel was prepared as follows: a 50 ml polypropylene conical tube (Becton Dickin- 2 g of xanthangum, 20 ml of glycerol, and 2 drops son, Franklin Lakes, NJ, U.S.A.) for the experiment. of 0.1% (w/v) hyaluronic acid were dissolved in The effective concentration of BP in pharmaceutical 500 ml of distilled water.22) These homemade cos- preparations ranges from 0.01 to 0.1% (w/v).18) All metic formulations contained either 0.1 or 0.05% of the experiments were performed with shielding (w/v) BP. from light. Statistical Analysis —— All data were subject to a Determination of FA —— The concentration of FA one-way analysis of variance. A p-value < 0.05 was was determined according to the method of Fung considered to indicate significant difference. and Groslean using formalin as the standard.19, 20) Briefly, 10 ml of 2,4-dinitrophenylhydrazone di- luted in 2N H3PO4 [0.02% (w/v)] was added to 5 ml RESULTS of test solution, and left standing at ambient temper- ature for 20 min. The mixture was extracted with Effect of Temperature on Release of FA upon the 5 ml of ethyl acetate for 20 min, and the ethyl acetate Decomposition of BP layer diluted with acetonitrile to × 5 was subjected BP test solution [0.1% (w/v)] was prepared us- to HPLC. The chromatographic peak of the com- ing a 0.005 M sodium phosphate buffer (pH 6.0), plex was confirmed by comparing its retention time and incubated for 90 min in water baths of 25◦C, and UV spectra. The concentrations were obtained 40◦C, and 60◦C. The release of FA upon the de- by interpolation on standard curves. The forma- composition of BP was dependent on temperature lin was standardized by the method of the Japanese (Fig. 1). The concentration of FA in the test buffer Pharmacopoeia.21) HPLC was carried out using a solution incubated at 60◦C for 90 min reached about Shimadzu Prominence instrument equipped with a 50 ppm. A significant difference among the respec- photodiode array detector. The determination wave- tive groups was recognized (p < 0.001). length was set at 355 nm. An Octadecyl silanized silicagel (ODS) column of L-column (5 µm, 4.6 mm Effect of Test Solution pH on Release of FA and I.D. × 150 mm, C.E.R.I., Saitama, Japan) was used. Decomposition of BP The mobile phase was acetonitrile: water (1 : 1) de- The pH of marketable cosmetics ranges from livered at a flow rate of 1.0 ml/min. The column 2.0 to 8.0.23) BP test solutions [0.1 or 0.01% (w/v)] temperature was held at 30◦C, and the volume of were prepared with several pH values (2.0, 4.0, sample injected was 10 µl. Determination of BP —— The concentration of BP was determined according to the method of Wang with some modifications.16) Briefly, each test solution was directly analyzed by HPLC with a pho- todiode array detector. BP standard solution was prepared with methanol. The chromatographic peak was confirmed by comparing its retention time and UV spectra. The concentration was obtained by in- terpolation on standard curves. The conditions for HPLC were as follows. The column used was a SU- PELCOSIL LC-18 (5 µm, 4.6 × 250 mm), and was operated at 30◦C. The mobile phase consisted of methanol: water: orthophosphoric acid (20 : 980 : 1) and the flow rate was 1.0 ml/min. The determina- tion wavelength was 210 nm. The volume of sam- ple injected was 10 µm. The HPLC system was as described above. Fig. 1. Effect of Temperature on Release of FA upon Decom- Preparations of Homemade Cosmetics (Lotion position of BP BP test solutions [0.1% (w/v)] were prepared with 0.005 M and Jell) —— The lotion was prepared as follows: sodium phosphate buffer (pH 6.0). Each value represents the mean 12.5 g of urea, 1.25 ml of glycerol, and 5 drops ± S.D. (n =3).; Incubated in a water bath at 60◦C, ;40◦C, ;25◦C. 490 Vol. 54 (2008) 6.0, and 8.0) of diluted 0.005 M sodium phosphate amount of FA released upon decomposition of BP buffer, and stored in a constant temperature box at in Osaka (Fig. 4). BP test solution [0.1% (w/v)] was 25◦C for 50 days. The release of FA upon the de- prepared with a 0.005 M sodium phosphate buffer composition of BP was dependent on pH (Fig. 2). A (pH 6.0), and stored at ambient temperature for marked FA-releasing effect was evident in alkaline 30 days. The experiment was conducted three times buffer compared with the acidic buffer. When BP in different seasons (mid-winter, early spring, and solution prepared with weakly alkaline buffer [pH early summer). It was found that release of FA upon 8.0, 0.1% (w/v)] was stored for 24 hr, the concentra- decomposition of BP markedly differed among the tion of FA reached 30 ppm.