Elevated formaldehyde concentration in ''Brazilian keratin type'' hair-straightening products: A cross-sectional study
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ORIGINAL ARTICLE
Elevated formaldehyde concentration in ‘‘Brazilian
keratin type’’ hair-straightening products:
A cross-sectional study
Mbulelo H. Maneli, PhD,a Peter Smith, PhD,b and Nonhlanhla P. Khumalo, FCDerm, PhDa
Cape Town, South Africa
Background: Brazilian keratin treatment (BKT) and similar straightening products fix and retain a straight
shape even when the hair is wet. Unacceptably high concentrations of formaldehyde have been reported in
such products.
Objective: We sought to measure the formaldehyde concentration in all BKT brands marketed in South
Africa in 2012.
Methods: We quantified formaldehyde by high-performance liquid chromatography with ultraviolet light
detection after derivatization with dinitrophenylhydrazine. All components of 7 identified commercial
brands were each tested 3 times.
Results: The maximum safe concentration of formaldehyde set by the US Cosmetic Ingredient Review
Expert Panel is less than 0.2%. Of the 7 commercial BKT brands, 6 had formaldehyde levels that ranged
from 0.96% to 1.4%, ie, 5 times higher than the recommended level; these included 5 brands labeled
formaldehyde-free.
Limitations: The study is limited by not including all internationally available BKT products.
Conclusions: Formaldehyde concentrations in BKT products may exceed recommended levels and serve
as a health hazard. Industry monitoring is needed to improve compliance and protection of hairdressers
and consumers. ( J Am Acad Dermatol 10.1016/j.jaad.2013.10.023.)
Key words: Brazilian keratin treatments; formaldehyde; hair; hairdressing; public health.
H eat straightens hair by breaking down
temporary hydrogen bonds found between
keratin filaments, but the effect is lost when
the hair gets wet. A Brazilian mortician is said to have
Abbreviations used:
BKT:
DNPH:
DNPHF:
Brazilian keratin treatment
dinitrophenylhydrazine
formaldehyde dinitrophenylhydrazone
invented a method where keratin fibers in heat- HPLC: high-performance liquid
straightened hair are cross-linked to retain a straight, chromatography
water-resistant shape for up to 3 months. The con-
venience and popularity of long-lasting straight hair
has resulted in a flood of products. These brands are levels of formaldehyde.1,2 The Cosmetic Ingredient
known by various names.1 Review was established in 1976 by the industry trade
Brazilian keratin treatments (BKT) and similar association (now the Personal Care Products
products internationally and in the United States Council), with the support of the US Food and
have been reported to contain unacceptably high Drug Administration and the Consumer Federation
From the Division of Dermatologya and Division of Pharma- University of Cape Town, Observatory 7925, South Africa.
cology,b Groote Schuur Hospital, University of Cape Town. E-mail: n.khumalo@uct.ac.za.
Supported by the National Research Foundation (South Africa). Published online December 8, 2013.
Conflicts of interest: None declared. 0190-9622/$36.00
Accepted for publication October 11, 2013. Ó 2013 by the American Academy of Dermatology, Inc.
Reprint requests: Nonhlanhla P. Khumalo, FCDerm, PhD, http://dx.doi.org/10.1016/j.jaad.2013.10.023
Division of Dermatology, Ward G23, Groote Schuur Hospital,
12 Maneli, Smith, and Khumalo J AM ACAD DERMATOL
of America.3 According to the Cosmetic Ingredient Sampling
Review Expert Panel, formaldehyde is safe to use at a Samples were stored at ambient temperature
maximum concentration of 0.2% as a preservative in until formaldehyde measurements, which occurred
consumer products.4 Formaldehyde may cause within 2 months of delivery. Three samples
respiratory irritation, contact dermatitis, headaches, (treatment, shampoo, and conditioner) of each
and pregnancy complications.5 Formaldehyde is brand were analyzed for formaldehyde concentra-
classified as a carcinogen; chronic exposure to high tion. Each sample was tested 3 times and a mean
concentration is associated and SD calculated for
with respiratory and hemo- comparison.
poietic malignancies.6,7 CAPSULE SUMMARY
Methods of formaldehyde Preparation of 2,4-DNPH
dFormaldehyde concentrations of up to
detection in cosmetics are solutions: Brady reagent
0.2% are recommended for use in
well established and include The solution of 0.18-mol/
consumer products. High concentrations
microdiffusion apparatus L 2,4-DNPH reagents was
increase risks of cancers and of
with fluorescent illumina- prepared following protocol
respiratory and pregnancy abnormalities.
tion, polarography, thin- by Ruekberg and Rossini.8 A
layer chromatography, dUsing high-performance liquid total of 3.0 g of powdered
colorimetry that involves chromatography; 6 of 7 ‘‘Brazilian keratin 2,4-DNPH was suspended in
reaction of formaldehyde type’’ hair brands had formaldehyde 20 mL of water and 70 mL of
with chromotropic acid, concentrations of 0.96% to 1.4%. This 95% ethanol followed by
2,4-dinitrophenylhydrazine included 5 brands labeled formaldehyde- slow addition of 15 mL of
(DNPH) or acetylacetone, free. concentrated sulfuric acid at
high-performance liquid d
Protective clothing is recommended for 108C. Dissolution of 2,4-
chromatography (HPLC), occupations with high formaldehyde DNPH was completed by
and mass spectrometry. exposure; this is currently not available heating the resulting
Measurement of formal- to hairdressers. Use of these products reddish-yellow solution until
dehyde that relies on the requires regulatory review and all 2,4-DNPH particles has
reaction of formaldehyde monitoring. dissolved or until tempera-
with 2,4-DNPH8 (condensa- ture reached 608C.
tion reaction) to form a stable
complex and quantification by HPLC is most reli- Derivatization of formaldehyde in BKT hair
able.8 HPLC is the technique of choice as it permits care product and extraction
both instrumentation and quantification to be auto- A total of 1 g of cosmetic product was suspended in
mated. It is highly specific and has a selective excess (approximately 6.0 mL) of 0.18 mol/L of
detection limit, in water, of approximately 6 parts 2,4-DNPH. The resulting emulsion, containing a red
per billion. Further, derivative maximum absorbance or yellow precipitate of the formaldehyde derivative
at wavelength 365 nm greatly reduces interferences.9 or formaldehyde 2,4-dinitrophenylhydrazones (2,4-
We aimed to determine concentrations of formal- DNPHF), was vortexed and left standing at ambient
dehyde in BKT brands sold on the South African temperature for at least 10 minutes. The 2,4-DNPHF
market by HPLC with ultraviolet detection after was vigorously extracted into 10.0-mL dichloromethane
derivatization with 2,4-DNPH. and 2,4-DNPHF was diluted 50 times to 1.0-mL volume
with methanol before HPLC injection.
METHODS
Material HPLC analysis
An attempt was made to identify all BKT products The HPLC column method by Benassi et al9 was
sold in South Africa from catalogs of large retailers and used on Shimadzu LC 10A instrument series (Tokyo,
local World Wide Web sites that advertise hair products. Japan). Briefly, 2,4-DNPHF was subjected to flow
Samples of identified product were purchased through through Agilent Eclipse XDB-C18 column (Agilent
the Internet in the first quarter of 2012. Chemistry Technologies, New Castle, DE), 5 m, 150 3 4.6 mm,
reagents 2,4-DNPH, dichloromethane, acetonitrile, where acetonenitrile and water (60:40, vol/vol), with
and sulfuric acid were analytical grade, and methanol a flow rate of 1 mL/min, served as mobile phase. The
was HPLC grade purchased from Merck (Pty) Ltd South volume of sample injected was 20 L and the
Africa (Modderfontein, South Africa). Formaldehyde absorption wavelength of a detector was set at 365
2,4-DNPH standard was obtained from Sigma-Aldrich nm. The signal peak area was used for quantitative
South Africa (Aston Manor, South Africa). calculation of formaldehyde. The calibration curve,J AM ACAD DERMATOL Maneli, Smith, and Khumalo 3
Fig 1. High-performance liquid chromatography of 2,4-dinitrophenylhydrazones (DNPHF)
(2,4-dinitrophenylhydrazine [DNPH] formaldehyde derivative) showing retention times
(x-axis) and concentration for detected signals (y-axis). A, Positive control. Peak detected
with the retention time of 16.0 minutes, which represents 2,4-DNPHF (sample: commercial
2,4-DNPHF). B, Negative control. Very low peak at 16.0-minute retention time reflecting little
(or no) 2,4-DNPHF and high peak at 12.8 minutes reflects excess or unused 2,4-DNPH (sample:
shampoo). C, Positive test result. Peak detected at 16.0-minute retention time represent
2,4-DNPHF (sample: Brazilian keratin treatment, brand B [Table I]).
in the concentration range of 0 to 25 g/mL, was obtained with the correlation coefficient very close
constructed by plotting 2,4-DNPHF peak area against to unity (R2 = 0.995). The 2,4-DNPHF peak area
its concentrations. The detection and quantitative was corrected for any interference found in blank
limit to the formaldehyde standard solution were sample by subtracting the average peak area of the
determined to be 3.31 g/L and 10.0 g/L, respec- interference in blanks from the 2,4-DNPHF peak
tively. The linear regression of y = 81,072x was areas in peaked samples.4 Maneli, Smith, and Khumalo J AM ACAD DERMATOL
Table I. Formaldehyde concentration in Brazilian This included 5 brands labeled formaldehyde-free
keratin type hair products and 1 labeled formaldehyde less than 0.2%.
BKT Formaldehyde Concentration, Concentration,
brand label mg/mL % DISCUSSION
A Formaldehyde-free 0.27 6 0.018 1.08 6 0.16 Formaldehyde is ubiquitous in household prod-
B Formaldehyde-free 0.28 6 0.00 1.08 6 0.00 ucts; in cosmetics it is used as a preservative at low
C Formaldehyde-free 0.27 6 0.0047 1.11 6 0.094 concentration (up to 0.2%). It is essentially used in
D 0.2% Formaldehyde 0.26 6 0.014 1.15 6 0.021 BKT products as a fixative that cross-links keratin
E Formaldehyde-free 0.31 6 0.016 0.96 6 0.11 amino acid side chains retaining the straight shape in
F None 0.18 6 0.014 1.40 6 0.51 hair. Initial reports of high formaldehyde concentra-
G Formaldehyde-free 0.055 6 0.010 0.17 6 0.040 tions preceded a flood of newer brands that claim to
contain low and no formaldehyde. Although con-
Formaldehyde was quantified by high-performance liquid
chromatography with ultraviolet light detection after derivatization centrations seem lower in newer brands, they are still
with 2,4-dinitrophenylhydrazine. Formaldehyde concentration was more than 1% formaldehyde10; and there are still
determined from a calibration curve constructed by plotting the reports of high concentration (eg, an average of 8%
formaldehyde 2,4-dinitrophenylhydrazone peak area against its was reported in US products advertized as contain-
concentrations (Fig 1, C ).
ing no formaldehyde).11
BKT, Brazilian keratin treatment.
The popularity of BKT products is increasing
worldwide. We tested 7 brands sold in the South
Confirmatory tests
African market at the time of the study. All advertised
Nuclear magnetic resonance and Fourier trans-
as international brands. We have not been able to
formed infrared spectroscopy10 techniques were
confirm that all were imported from Brazil. The
used to confirm the presence of formaldehyde in
concentration of formaldehyde in the products we
tested samples before quantification (data available
tested confirms recent international data,10 in spite of
on request).
much media attention and regulatory concern.
This study has limited generalizability because it
RESULTS did not including all internationally available BKT
HPLC analysis products. However, the false labeling of products
Free formaldehyde concentration in BKT cos- as formaldehyde-free exposes unsuspecting con-
metics was determined from known concentration sumers and hairdressers to adverse effects.
of 2,4-DNPHF. Fig 1, A, shows HPLC chromatogram Formaldehyde is unstable in its gaseous state
of 2,4-DNPHF standard solution. One main peak was and exists as a liquid (formalin) in cosmetic
detected at the retention time of 16.0 minutes, which products. At high temperatures, such as occurs
represents a 2,4-DNPH formaldehyde derivative when applying BKT products, formaldehyde gas is
(2,4-DNPHF). The peak area of 2,4-DNPHF is used released. A recent simulated air-quality study tested
to construct the standard curve from which the brands (including those labeled formaldehyde-free)
formaldehyde concentration is calculated. and found them to have ‘‘.concentrations that
Cosmetics (eg, shampoos and conditioners) with meet or exceed occupational exposure limits.’’12 At
low formaldehyde concentration display low peak high concentrations formaldehyde is listed as a
for 2,4-DNPHF and high peak for free 2,4-DNPH (Fig carcinogen and its use in industries is regulated
1, B), which indicate lower amount of 2,4-DNPH under strict air control. This is not the case in most
required to derivatize formaldehyde; the rest re- hairdressing salons where BKT products are used
mains in excess. The opposite is true for the daily.
treatment product that contains high formaldehyde Finally, high concentrations of formaldehyde were
concentration (Fig 1, C ). found even in products labeled formaldehyde-free.
Unlike pharmaceutical companies, there is no
Formaldehyde concentrations requirement to produce evidence of rigorous safety
Concentration of formaldehyde based on 2,4- testing before marketing new cosmetics. However,
DNPHF derivatives in shampoos, conditioners, and perhaps it is time that products known to contain (or
one of the treatment products was shown to be less to have mechanisms that function through) poten-
than 0.2%. Formaldehyde levels detected from BKT tially harmful ingredients should be required to clearly
products are tabulated below (Table I). For 6 BKT, list concentrations on labels. Random tests could then
formaldehyde concentration ranged from 0.96% to be used to monitor and influence industry practice in
1.4%, which is 5 times higher that the concentration the interest of consumer safety and occupational
set by the Cosmetic Ingredient Review Expert Panel. health. Compliance with and the adequacy of theJ AM ACAD DERMATOL Maneli, Smith, and Khumalo 5
recommendation that hair salons use air-monitoring 4. Cosmetic Ingredient Review Expert Panel. Final report on the
equipment requires evaluation.11 Decisions about safety assessment of formaldehyde. J Am Coll Toxicol 1984;39:
157-84.
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Hornung RW, Herrick RF, et al. Mortality from lymphohemato-
The authors are grateful to Anwar Jardine, PhD, and poietic malignancies and brain cancer among embalmers
Lutete Khonde, MSc, from the Department of Chemistry exposed to formaldehyde. J Natl Cancer Inst 2009;101:1696-708.
at University of Cape Town for assisting with nuclear 7. Schwilk E, Zhang L, Smith MT, Smith AH, Steinmaus C.
magnetic resonance tests. Formaldehyde and leukemia: an updated meta-analysis and
evaluation of bias. J Occup Environ Med 2010;52:878-86.
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