Background
People in many occupations are exposed to different requirements and stresses in their everyday working life. In hairdressing, women and men are exposed to physical and mental stress, as they have to stand for a long time. Moreover, they often come into contact with chemicals which are components in hair care products. The substances can be found in applications for dyeing or bleaching hair, for permanent waving and in styling products. The use of these preparations is an essential component of the occupation as hairdresser. Health can be impaired by the exposure to these chemicals. For example, widely used agents such as persulfates, organic solvents and endocrine disrupting chemicals were described in various reviews [
1‐
3]. The chemicals may be absorbed by inhalation and/or through skin contact and may cause a variety of diseases, e.g. of the skin or the respiratory tract or even cancer [
1,
4]. Officially recognised occupational diseases of male and female hairdressers include skin diseases, as well as toxic irritant and allergic obstructive airway diseases [
5‐
7]. There are numerous studies and publications on this topic in which different clinical pictures and triggering substances are described [
8‐
10]. In contrast to this, the effects of occupational exposure on fertility and pregnancy of hairdressers and the foetal development of their children have more rarely been described, although there has long been some evidence that there might be unfavourable effects on reproduction [
2].
For example, in 2007, 277,000 people were employed in the hairdressing occupation in Germany. Of these, 75% were 45 years old or younger. 90% of them were women; thus hairdressers are a significant group of employed women [
11]. Once occupational health risks from exposure in the workplace have been recognised, actions may be possible to minimise the risk of unfavourable birth outcomes or of unwanted infertility.
This systematic review gives an overview of publications of epidemiological studies on the association between occupational exposure in the hairdressing profession and their effects on the fertility and pregnancy of women in this occupational group.
Materials and methods
A search in MEDLINE from 1990-2010 was performed to search for epidemiological studies on health risks in hairdressers; the most recent update was performed on 31 May 2010. The key words refer to the occupational designations as well as to the different reproductive disorders. Diagnoses related to reproduction are especially unfavourable events, such as infertility and subfertility, prolonged time to pregnancy (TTP), spontaneous abortion, preterm birth, stillbirth, low birth weight (LBW < 2500g), small for gestational age (SGA), congenital malformations and delayed development of children. This led to the following search terms: hairdresser/s, hair stylist/s, hairdressing occupation, hairdressing profession, professional hairdressing or professional hair care in combination with reproductive disorders, reproductive outcomes, fertility, infertility, subfertility, menstrual disorders, pregnancy outcomes, malformations, preterm birth, stillbirth, perinatal death, low birth weight/LBW, small for gestational age/SGA, spontaneous abortion, as well as time to pregnancy/TTP.
Subsequently, further publications were identified from the lists of literature and used for the work.
The studies were selected in accordance with the following a priori defined inclusion criteria:
-
Study design: Limitation to original studies - reviews and empirical studies
-
Study content: With respect to the occupation as a risk factor and the occupational exposure
-
Study population: Occupation as male or female hairdresser
-
Outcome: Job-related health risks in reproduction
The studies are classified into occupational studies and hairdresser studies. Occupational studies examine multiple sections of the working population for a defined disease or exposure and differentiate the risks for different occupational groups. On the other hand, hairdresser studies define hairdressers as the study population and compare them with other populations or occupational groups with respect to health risks.
The most important characteristics and data of all included studies are shown in Tables
1 and
2. These present information on study design, place and time of the examination, as well as on the objective of the study and the tested population. Furthermore, the condition of the exposure and the results for the hairdressers are summarised. If single substances were mentioned as a possible cause of reproductive disorders in the hairdressing occupation, they are listed in the table. Descriptions of single publications can be found in the result section.
Table 1
Occupational studies: The risk of fertility disorders and pregnancy complications among hairdressers
Thulstrup 2006 | Review | Medline, 1966-2004 | Occupational exposures during pregnancy and birth defects | Employed women, 26 original studies | Occupation during pregnancy | Hairdressers No clear evidence for causal associations between maternal occupational exposures and specific birth defects |
Garlantézec 2009 | Cohort study | France, 2002-05 | Risk of malformations and exposure to solvents | 3,399 pregnant women (55 hairdressers) before 19th gestational week | Self-reported exposure (never/occasional/regular, job exposure matrix (JEM) no/medium/high exposure | Hairdressers Self-reported: regular exposure JEM-assessed: medium exposure |
Goulet 1991 | Case-control study | Canada, 1982-84 | Stillbirth and chemical exposure during pregnancy | 227 stillbirths (> 20 weeks of gestation), 227 live births | Women working full-time (> 30 h/week) at the beginning of pregnancy, occupation, specific exposure to chemicals (light/moderate/high) | Hairdressers Odds Ratio (OR) 0.1* (#CI 0.0-0.3) P = 0.05 |
Kuijten 1992 | Case-control study | USA, 1980-86 | Childhood astrocytoma (< 15 years) and parental occupation | 163 cases, 163 controls | Job categories, parental occupational history | Maternal occupation - hairdresser Preconception OR 2.5 (CI 0.4-26.2) Pregnancy OR 1.5 (CI 0.2-18) Postnatal OR 3.0 (CI 0.2-157.7) |
Cordier 2001 | Case-control study | Under IARC coordination in 7 countries, 1976-94 | Childhood brain tumours and parental occupations | 1,218 cases, 2,223 controls | Occupational history during 5-year period before child's birth | Maternal occupation - hairdresser OR 1.1 (CI 0.7-2.0) |
Olshan 1999 | Case-control study | Canada/USA, 1992-96 | Childhood neuroblastoma (< 19 years) and parental occupation | 538 cases, 504 controls | Occupational history, occupational groups | Maternal occupation - hairdresser OR 2.8 (CI 1.2-6.3) Paternal occupation - hairdresser OR 3.3 (OR 0.2-45.7) |
Bianchi 1997 | Case-control study | Italy, 1982-89 | Congenital malformations and maternal occupation | 1,791 cases, 3,223 controls | Maternal occupation during pregnancy | Hairdressers Orofacial clefts OR 2.2 (99% CI 0.4-10.7); Limb defects OR 2.2 (99% CI 0.8-6.1); multiple anomalies OR 1.7 (99% CI 0.7-4) |
Lorente 2000 | Case-control study | France/United Kingdom/Italy/Netherlands, 1989-92 | Orofacial clefts and maternal occupational risk factors | 100 cases (4 hairdressers), 751 controls (9 hairdressers) | Occupations before and during pregnancy, tasks, products handled, frequency of use | Hairdressers/beauticians Cleft palate only OR 5.1 (CI 1.01-25.9) Cleft lip with or without cleft palate OR 1.86 (CI 0.36-9.65) |
Nguyen 2007 | Case-control study | Norway, 1996-2001 | Orofacial clefts and parental occupation | 574 cases (without other malformations) (4 hairdressers), 763 controls (3 hairdressers) | Job title, industry type, status of work during early pregnancy (first 3 months) | Maternal occupation - hairdresser Cleft lip with or without palate OR 4.8* (CI 0.99-23) Cleft palate only OR 2.3* (CI 0.21-25) |
Ormond 2009 | Case-control study | England, 2000-03 | Hypospadias and maternal occupational exposures to endocrine disrupting chemicals (EDCs) | 471 cases, 490 controls | Job title, main tasks, self-reported exposure, job exposure matrix (JEM) | Hairdressers OR 2.59* (CI 0.7-12.3) Occupational exposure Hair spray OR 2.39*(CI 1.4-4.17) Phthalates OR 3.12*(CI 1.04-11.46) |
Mutanen 2001 | Register-based study | Sweden, 1958-96 | Childhood cancer and parental occupation | 8,185 cases < 15 years (45 hairdressers) | Job title | Hairdressers Kidney cancer (Father) Standardized Incidence Ratio (SIR) 10.6 (CI 2.9-27.2) (Mother) SIR 1.0 (CI 0.1-3.7) |
Vrijheid 2003 | Register-based study | England, Wales, 1980-96 | Hypospadias and maternal occupational exposure to EDCs | 3,471 cases (98 hairdressers), 35,962 controls -all congenital anomaly cases | Job title, exposure categories unlikely/possible/probable | Maternal occupation - hairdresser Observed/Expected Ratio (O/E) 0.99 (CI 0.81-1.19) (1980-89) O/E 0.94 (CI 0.74-1.17) (1992-96) O/E 1.18 (CI 0.8-1.64) |
Table 2
Hairdresser studies: The risk of fertility disorders and pregnancy complications among hairdressers
Kersemaekers 1995 | Review | Medline, 1985-1993 | Reproductive disorders due to chemical exposure | Hairdressers; 9 studies | Hair washing, hair bleaching, hair dyeing, permanent waving, hair styling, solvents | Inconsistent results of studies, little evidence, reproductive risks cannot be excluded |
Kersemaekers 1997 | Cohort study | Netherlands, 1986-88, 1991-93 | Reproductive disorders | 4,236 hairdressers, 2,932 clothing sales clerks | Work at least 10 hours/week during the first 2 months of pregnancy | 1st period: Spont. abortion OR 1.6 (#CI 1.0-2.4) Time to pregnancy (TTP) > 12 months OR 1.5 (CI 0.8-2.8) Low birth weight (LBW) OR 1.5 (CI 0.7-3.1) 2nd period: Abortion OR 0.9 (0.7-1.1) |
Kersemaekers 1997 | Cohort study | Netherlands, 1986-88, 1991-93 | Neurodevelopment in offspring | 4,236 hairdressers, 2,932 clothing sales clerks | Work at least 10 hours/week during the first 2 months of pregnancy | 1st period: 1st word RR 2.4 (CI 1.1-5.1) 1st sentence RR 4,1 (CI 1.2-13.6) Seizures during fever RR 2.6 (CI 1.0-6.9) 2nd period: Decreased risks of seizures, no delayed child development |
Rylander 2002 | Cohort study | Sweden, 1973-94 | Reproductive outcome | 3,706 hairdressers, 3,462 reference population | Working time/week, treatments/week for permanent waving, hair dyeing, bleaching, shampooing, spraying | Small for gestational age (SGA) OR 1.4 (CI 1.1-1.7) Malformation OR 1.3 (CI 1.1-1.6) LBW OR 1.2 (CI 1.0-1.5) Preterm birth OR 1.1 (CI 0.9-1.3) |
Zhu 2006 | Cohort study | Denmark, 1997-2003 | Pregnancy outcomes and developmental milestones children | 550 hairdressers, 3,216 shop assistants | Working time/week, work postures | SGA OR 1.0*(CI 0.7-1.3) Preterm birth OR 1,0*(CI 0.7-1.6) Malformation OR 0.8*(CI 0.6-1.2) Fetal loss (spont. abortions + stillbirths) OR 0.7*(0.3-1.8) no differences in child development |
Blatter 1993 | Cross-sectional study | Netherlands, 1990 | Menstrual disorders due to chemical exposure | 64 hairdressers, 130 clothing shop assistants | | Irregular cycle OR 2.4 (CI 1.1-5.2) Oligomenorrhoea OR 3.0 (CI 1.1-8.4) Unusual cycle length OR 3.4 (CI 1.5-7.8) Long blood loss OR 5.1 (CI 1.7-15.4) Severe pain OR 2.6 (CI 1.2-5.9) |
Gan 2003 | Cross-sectional study | China | Health effects due to exposure with permanent waving solution | 57 hairdressers, 64 schoolteachers | Permanent waving procedure > 1 year | Menstrual disorders (menoxenia) Hairdressers 22.81% vs. reference 9.38% (p < 0.05) |
Ronda 2009 | Cross-sectional study | Spain, 2006 | Menstrual disorders and subfertility | 310 hairdressers, 310 shop assistants + office workers | No. of years in occupation, daily working hours previous year | Subfertility OR 2.17*(CI 0.91-5.17) Menstrual disorders OR 1.87*(CI 0.99-3.91) |
Ronda 2010 | Cross-sectional study | Spain, 2006 | Pregnancy outcomes | 310 hairdressers, 310 shop assistants + office workers | Job tasks, application of chemical products, ventilation | Spontaneous abortion OR 1.6*(0.9-2.7) Preterm birth OR 1.0*(0.4-2.9) LBW OR 0.2*(0.3-2.0) |
Axmon 2006 | Cross-sectional study | Sweden, 2000 | Fertility/ time to pregnancy for wanted pregnancy and miscarriage risk | 1,678 hairdressers, 1,578 referents population | Exposure before and during pregnancy, job tasks, ventilation | Fertility Fertility ratio (FR) 0.91 (CI 0.83-0.99) Spontaneous abortion OR 1.12 (CI 0.88-1.42) |
Baste 2008 | Cross-sectional study | Norway, 1997-99 | Infertility, spontaneous abortion and smoking habits | 136 hairdressers, 593 shop assistants/ 6,734 other occupations | Income for at least 100 hours in occupation last year | Infertility RR 1.3*(CI 1.08-1.55) Abortion RR 1.31*(CI 1.07-1.6) Hairdressers, never smoker: Infertility RR 2.01 (CI 1.45-2.8) Abortion RR 2.0 (CI 1.48-2.72) |
Gallicchio 2009 | Cross-sectional study | USA, 2005-08 | Premature ovarian failure (POF) | 443 hairdressers, 508 controls | Work history, employment status | POF RR 1.9*(CI 0.76-4.72) Caucasian women POF RR 3.24*(CI 1.06-9.91) |
Rylander 2005 | Register-based study | Sweden, 1983-2001 | Reproductive outcome | 8,384 hairdressers, reference: all deliveries 1983-2001 for working mothers | Working time during pregnancy (full-time/part-time) | SGA OR 1.19*(CI 1.07-1.33) LBW OR 1.10*(CI 0.99-1.21) Preterm birth OR 1.05*(CI 0.96-1.14) |
Hougaard 2006 | Register-based study | Denmark, 1998-2002 | Risk of infertility | 68 hairdressers, reference: all working women (20-44 years) + shop assistants | Economically active in registration | Infertility Relative risk (RR) 1.01 (CI 0.77-1.29) compared to shop assistants, RR 0.93 (CI 0.72-1.18) compared to all working women |
Axmon 2009 | Register-based study | Sweden, 1996 | Comparison of birth weight and foetal growth | 3,137 hairdressers and their sisters (3,952) | Graduates of vocational schools for hairdressers | Large for gestational age (LGA) OR 0.60*(CI 0.39-0.92), LBW OR 0.72*(CI 0.5-1.03), SGA OR 0.85*(CI 0.54-1.34) |
Halliday-Bell 2009 | Register-based study | Finland, 1990-2004 | Adverse pregnancy outcome | 10,622 hairdressers, 2,490 beauticians, 18,594 teachers | Working as a hairdresser | Hairdressers compared to teachers LBW OR 1.44*(CI 1.23-1.69) Preterm birth OR 1.21*(CI 1.07-1.38) SGA OR 1.65*(CI 1.38-2.07) Perinatal death OR 1.62*(CI 1.01-1.60) |
Additionally, the risk estimate for the target diagnosis of each study is presented in Table
3 and classified into statistically significant, not statistically significant deviation from one (risk estimate ≥ 1.5 or ≤ 0.5) and no association.
Table 3
Summary of epidemiological studies on the occupational risk of reproductive disorders among hairdressers
Infertility | + | | | |
| | | ± | |
Subfertility | | + | | |
Time to pregnancy
| | + | | |
Menstrual disorders§ | + | | | |
| | + | | |
Premature ovarian failure | | + | | |
Spontaneous abortion | 1st period + | | 2nd period ± | |
| | | ± | |
| | | ± | |
| | | ± | |
| + | | | |
Preterm birth | | | ± | |
| | | ± | |
| | | ± | |
| + | | | |
Stillbirth | - | | | |
| | | ± | |
Perinatal death | + | | | |
Small for gestational age | + | | | |
| + | | | |
| | | ± | |
| | | ± | |
| | | ± | |
| + | | | |
Large for gestational age | - | | | |
Low birth weight | | + | | |
| + | | | |
| | | ± | |
| | | ± | |
| + | | | |
Congenital malformation§ | | + | | |
| + | | | |
| | | ± | |
Hypospadias
| | | | |
| | + | | |
Orofacial cleft
| | + | | |
| | + | | |
Cleft palate
| | | | |
Cleft lip
| | + | | |
| | | ± | |
| + | | | |
Cancer | | | | |
Kidney cancer
| Father + | | Mother ± | |
Astrocytoma
| | + | | |
Neuroblastoma
| Mother + | Father + | | |
Brain tumour
| | | ± | |
Delayed child | 1st period + | | 2nd period ± | |
development | | | ± | |
Discussion
This systematic review focuses on the effects of occupational exposure to chemical substances in hair care products on fertility and pregnancy in hairdressers. The review shows that the results of the included studies are inconsistent. No unambiguous association between the exposure in the workplace and the risk of reproductive disorders can be derived from the described studies. However, evidence for a possible increase in risks has been found repeatedly.
Studies on reproduction in hairdressers often target specific outcomes and the occurrence and frequency are compared with other population groups. The effects of specific substances on fertility and pregnancy in hairdressers are rarely the main focus.
Pregnancy outcomes were investigated in several studies with a wide range of different diagnoses. One of the most frequently examined outcomes in this context was the risk of spontaneous abortion among hairdressers. Increased risks were found in the study by Baste [
33] and a Dutch cohort study, although this effect disappeared in the second study period [
25]. Other studies did not identify any association between occupational exposure and spontaneous abortion [
28,
31,
32]. An elevated risk of preterm birth in hairdressers was only found by Halliday-Bell [
38]; other studies showed no differences between hairdressers and controls [
27,
28,
31]. When considering deliveries of SGA newborns, a Swedish cohort study [
27] and 2 register-based studies [
35,
38] found statistically significant effects among hairdressers. In contrast to this, the same number of studies did not find any association [
28,
31,
37]. Similar findings were seen for the risk of LBW. A cohort study [
27] and a register-based study [
38] observed increased risks, and Kersemaekers et al. described a non-significant risk for hairdressers [
25], although two studies did not confirm these results [
35,
37]. A further unfavourable pregnancy outcome is the occurrence of congenital malformations in offspring. Statistically significant associations were found for major malformations [
27] and cleft palate only [
13]; non-significant risks were observed for major malformations [
12], hypospadias [
21], orofacial clefts [
12,
20] and cleft lip [
13]. No association was found between the risk of congenital malformations and the occupational exposure of hairdressers in 2 studies [
14,
28]. Malformations and childhood cancer were most often investigated in explorative studies, meaning that the studies related pregnancy outcomes to occupation in general and subsequently reported findings for hairdressers specifically. One of these studies found an increased risk of kidney cancer in the children of male hairdressers; no similar results were seen in the children of female hairdressers [
22]. On the contrary, an association between neuroblastoma and maternal occupation were observed for hairdressers. No risk for the children of male hairdressers was found [
19]. One study examined childhood astrocytoma and identified an increased although not significant risk for female hairdressers [
17]. Brain tumours in children did not show any associations with the work environments of hairdressers [
18]. Additional diagnoses were investigated more rarely. All results can be found in Table
3.
As shown in the review, the reports present varying results as regards reproductive disorders. Therefore, it is still possible that the health of hairdressers is at risk with respect to fertility and pregnancy.
Similar results were found in a review by Kersemaekers et al. 15 years ago [
2]. To our knowledge, this is the only review to date that focused on reproductive disorders among hairdressers directly, even if they were only able to review a very small number of specific hairdresser studies. However, today additional studies on the reproductive risk of hairdressers are available, but inconsistent methods, outcomes and results make the drawing of conclusions difficult. There are several reasons why the studies are so inconsistent. First, the conception of reproductive disorders implicates a broad variety of adverse outcomes from infertility and other pre-pregnancy disorders to events during the perinatal or postnatal period through to child development. Second, a total of 26 original studies performed since 1990 were identified and only 15 studies are specific investigations on the exposure of hairdressers. The remaining studies are occupational studies and related pregnancy outcomes to occupation in general. Neither a comparison of the studies nor a final assessment is possible.
Thirdly, factors which explain the inconsistent results could include differences in treatments and fashion trends, differences in education and training between countries, changes in occupational environment, as well as different study designs and different reference populations.
Two different examination methods are used for risk assessment. The occupational studies focus on employees or specific exposure in general. With this study design, many occupational groups are examined, with the consequence that only a few hairdressers are included in the assessment. Small sample sizes lead to a low statistical power. This could be an explanation why in some studies elevated risks occurred in male or female hairdressers, but these were not statistically significant [
12,
20,
21]. Based on the variety of occupations, the exposure can only be assessed very roughly, as a specific exposure is predominantly assigned to each occupational group and not as often on the basis of the actual work performed. However, such studies are important as they give evidence for possible health risks, which can be investigated through further studies.
In contrast to this, the hairdresser studies focus on the group of hairdressers and compare them with other occupational and/or population groups with respect to their occupational risk as regards reproduction. Assistants in clothing shops are preferred as a control group as they are considered to be rather similar with respect to the level of education, socioeconomic standing, and the physical and mental workloads. Additionally, different exposure in the workplace can be assumed, with the result that health risks for hairdressers can be observed as a factor of the activities typical of their occupation. Differences in age and smoking behaviour are often controlled by adjustment. With the exception of methodological deficiencies, this study design gives clear statements on hairdressers with respect to their risks. Many hairdressers participate in these studies and the exposure can be assessed more exactly.
Exposure comparable to that of the hairdressers can be assumed for the group of beauticians. In some countries hairdressers may also called cosmetologists, stylists or beauticians. Some studies have reported increases in the risks of spontaneous abortions [
24], SGA [
38] and low birth weights of children [
39], as well as orofacial clefts [
13]. Other studies did not find any association between occupational exposure among cosmetologists and menstrual disorders [
40], infertility [
41], congenital malformations [
42], and other adverse pregnancy outcomes [
43].
The exposure assessment is an essential problem in occupational studies. The assessment is used very differently in individual studies and ranges from the simple designation of the occupation "hairdresser" to the differentiated designation of the activity during which individual hair cosmetics are used, as well as their times of use. However, the occupation alone cannot serve as a substitute for data on exposure itself, as this does not permit its exact determination. Occupation only provides a rough measure of exposure, which can vary within the occupational group. Consequently, the assessment of the actual risks for hairdressers is very inaccurate and can possibly underestimate or overestimate the risks of hairdressing. A valid exposure assessment is necessary for an exact assessment of the occupational situation resulting in health risks. Hairdressing work can be associated with a variety of chemical contacts, which arise through the use of hair care products for washing, dyeing, bleaching, styling, spraying, as well as for perming, and media for cleaning and disinfecting the workplaces. In this environment, exposure is predominantly dermal or inhalative and depends in particular on the duration and frequency of the performed activities and their intensity. Precautions can minimise the exposure. If the room is adequately ventilated and the hairdresser wears gloves, the chemical exposure at the workplace can be reduced [
44,
45].
Another essential aspect is the study period. The working environment and also the hairdressing occupation are subject to constant change: older products are taken off the market and new formulations are used. Legal regulations and recommendations (e.g. for ventilation, for using gloves or for substituting or prohibiting certain ingredients) are changed due to new knowledge and thus can influence the exposure at the workplace and the health risks of hairdressers. Through the assessment of two time periods before and after changing the regulations in the Netherlands, the study of Kersemaekers et al. shows that the risks of pregnancy complications and developmental disorders was clearly reduced as a result of improved working conditions [
25,
26].
In addition to chemical exposure, the daily working time and physical stress, such as standing for a long period of time and unfavourable working postures, additionally influence the health of hairdressers. In a systematic review, Bonzini et al. showed that these factors increased the risk of preterm births and LBW children [
46]. A meta-analysis confirmed associations between physically demanding work and preterm birth and SGA [
47]. However, hairdressers were not considered in the studies.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
MH has made substantial contributions to the interpretation of data and has been involved in revising the manuscript critically for important intellectual content.
MD has made substantial contributions to the interpretation of data and has been involved in revising the manuscript critically for important intellectual content.
AS has made substantial contributions to the interpretation of data and has been involved in revising the manuscript critically for important intellectual content.
JTC has made substantial contributions to the interpretation of data and has been involved in revising the manuscript critically for important intellectual content.
AN has made substantial contributions to conception and design, the interpretation of data and has been involved in drafting and revising the manuscript critically for important intellectual content.
CP has made substantial contributions to conception and design, acquisition of data, the interpretation of data and has been involved in drafting and revising the manuscript.
All authors have read and approved the final manuscript.