Incidence and characteristics of chemical burns

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Incidence and characteristics of chemical burns Dong-Hee Koh a, Sang-Gil Lee b, Hwan-Cheol Kim c, * a Department of Occupational Environmental Medicine, International St. Mary’s Hospital, Catholic Kwandong University, Incheon, South Korea b Occupational Safety and Health Research Institute, Korea Occupational Safety and Health Agency, Ulsan, South Korea c Department of Occupational and Environmental Medicine, Inha University School of Medicine, 100 Inharo, Nam-gu, Incheon, South Korea

article info

abstract

Article history:

Objectives: Chemical burns can lead to serious health outcomes. Previous studies about

Accepted 31 August 2016

chemical burns have been performed based on burn center data so these studies have

Available online xxx

provided limited information about the incidence of chemical burns at the national level. The aim of this study was to evaluate the incidence and characteristics of chemical burns using

Keywords: Chemical burns Burns Corrosion

nationwide databases. Methods: A cohort representing the Korean population, which was established using a national health insurance database, and a nationwide workers’ compensation database were used to evaluate the incidence and characteristics of chemical burns. Characteristics of the affected body region, depth of burns, industry, task, and causative agents were analyzed from two databases. The incidence of chemical burns was calculated according to employment status. Results: The most common regions involving chemical burns with hospital visits were the skin followed by the eyes. For skin lesions, the hands and wrists were the most commonly affected regions. Second degree burns were the most common in terms of depth of skin lesions. The hospital visit incidence was 1.96 per 10,000 person-year in the general population. The compensated chemical burns incidence was 0.17 per 10,000 person-year. Employees and the self-employed showed a significantly increased risk of chemical burns undergoing hospital visits compared to their dependents. Conclusion: Chemical burns on the skin and eyes are almost equally prevalent. The working environment was associated with increased risk of chemical burns. Our results may aid in estimating the size of the problem and prioritizing prevention of chemical burns. ã 2016 Elsevier Ltd and ISBI. All rights reserved.

1.

Introduction

Burns are one of the most common occupational injuries. Burns can be caused by heat, electricity, or chemical exposure. Chemical burns are reported to comprise 1.4–8.5% of all admission cases due to burns [1]. Chemical burns can lead

to serious health outcomes, including skin burns benefiting from skin grafts. For example, severe hydrofluoric acid burns can lead to skin burns as well as life-threatening hypocalcemia, which can eventually lead to death. Chemical burns on the eyes can also lead to permanent damage in visual function [2]. Inhalation or ingestion of caustic agents can cause severe complications in internal organs such as the esophagus and

* Corresponding author. E-mail address: [email protected] (H.-C. Kim). http://dx.doi.org/10.1016/j.burns.2016.08.037 0305-4179/ã 2016 Elsevier Ltd and ISBI. All rights reserved.

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lungs, even leading to death. Even in milder cases, reactive airway dysfunction syndrome (RADS) can also occur after inhalation of acid or alkali [3]. The causative agents of chemical burns may vary according to geographical location, population structure, and industrial structure. Acids and alkalis are the most common types of causative agents involved in chemical burns. For acids, sulfuric acid, hydrochloric acid and hydrofluoric acid are representative agents, and for alkalis, sodium hydroxide and potassium hydroxide are representative agents. Both acid and alkali agents can cause immediate skin burns when one is exposed. Acids and alkalis are extensively used in electroplating and semiconductor manufacturing industries. These are also widely used in various industries including wastewater treatment facilities, laboratories and restaurants. Solvents also can cause skin burns. For example, contact with dichlormethane does not cause burns immediately but when the contact is prolonged (e.g., a worker wears a glove with a pin-hole and does not recognize it for several hours) it causes skin burns [4]. Other chemicals such as white phosphorus used for ammunition production can also cause chemical burns [5]. The various causative agents and affected body parts extracted from the literature are listed in Supplementary Table 1. Chemical burns can occur in occupational settings, domestic non-intentional injury and criminal assault, but occupational settings are reported to comprise up to 67.8% of all chemical burns admissions [6]. Chemical burns often lead to serious health problems and disabilities. To prevent chemical burns, epidemiological studies regarding the incidence and characteristics are necessary as a priority. Many studies examined characteristics of chemical burn in terms of demographics of patients, causative agents, depth of burn, and total burn surface area (TBSA). However, these studies were mainly conducted by reviewing records of patients admitted in burn centers [7]. These burn center-based studies provided detailed information on chemical burns but because these studies were based on severe cases with admission to hospitals, it has been impossible to estimate the overall incidence including minor chemical burns which did not undergo admission. According to Heinrich’s rule, for every one major injury in the workplace, 29 are minor injuries and 300 cause no injuries [8]. Aforementioned studies have limitations to estimate the overall size of chemical burns, and in addition, these studies could only provide the incidence in regions where hospitals were located. In the present study, we aimed to estimate the chemical burn incidence in the general Korean population using representative, nationwide databases. In addition, we intended to examine characteristics of chemical burns, which would aid efforts to prevent chemical burns.

Program (MAP) [9]. NHIS has collected claim data, including eligibility data and medical treatment records. Recently, the NHIS publicly released the National Health Insurance ServiceNational Sample Cohort (NHIS-NSC) database. The NHIS-NSC consisted of one million Koreans (2% of the population) sampled from the entire population in 2002 using a complex multistage sampling method [10]. The eligibility status of the one million Koreans, medical treatment records, and periodic health checkups records were all followed until 2013 and were integrated into the NHIS-NSC database. We used this NHISNSC database to elucidate the incidence and characteristics of chemical burns. We restricted the study period from 2009 to 2013. The reason in this regard was that the medical treatment records of the people under the MAP were incomplete before 2008 in the NHIS-NSC. We used 2008 data for detecting non-incident cases, thus, we excluded chemical burn subjects who visited the hospitals for out- or in-patient care both in 2008 and 2009, consecutively. We further restricted age groups to between 20 and 60 years of age because we aimed to examine chemical burns in the working age population. Chemical burns cases were operationally defined using the Korean Classification of Diseases (KCD) code which was based on the 10th revision of the Internation Classification of Diseases (ICD-10). The three-digit ICD codes for chemical burns are listed in Table 2. Chemical burns were categorized by the body part of the burns, the depth of the burns, and the extent of the burns (TBSA). The body parts afflicted by the chemical burns were simply categorized into skin, eye (T26), and internal organs (respiratory (T27) and gastrointestinal tract (T28)). Skin chemical burns were sub-categorized into five regions in terms of affected region: head & neck (T20), shoulder & trunk (T21), upper extremities (T22), hand & wrist (T23), lower extremities (T24), and foot &ankle (T25). For classifying the depth of chemical burns on the skin (T20-T25, T29, T30), the 4th digit of the ICD was used: 4, 5, 6, 7 represent unspecific, first, second, and third degree burns, respectively. Only a few cases were recorded using the extent of chemical burns (T32 code). If a patient visited a hospital between 2009 and 2013 and the conditions were coded as one of the chemical burns, the patients were regarded to have had a chemical burn. In the NHIS system, insured persons are divided into ‘employee insured’ and ‘self-employed insured’ [11]. The selfemployed insured is a category other than the employed insured and its dependents include self-employed persons, farmers and fishermen. We further divided the insured category into three groups in terms of job status: employee (employee insured policyholder), self-employed (self-employed policyholder), and dependents (dependents of employee insurance policyholders or self-employed insurance policyholders, or people under the MAP).

2.

Methods

2.2.

2.1.

Data source for the general population

Korea has a single workers’ compensation insurance system which is operated by the Korea Workers’ Compensation & Welfare Service (COMWEL) [12]. It covers all workplaces with one or more workers. An average of 1.7 million companies and 14.7 million workers between 2009 and 2013 were

Korea has a single insurer system which is operated by the National Health Insurance Service (NHIS). The NHIS covers all citizens, except for 3% of the population under the Medical Aid

Workers’ compensation data

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covered by the workers’ compensation system [13]. If a worker is treated through this workers’ compensation system, his or her claim will not be presented in the NHIS database, thus the NHIS and workers’ compensation database are mutually exclusive. We obtained nationwide data of chemical burns that were compensated for, for the years 2009–2013 from the workers’ compensation database. The data consisted of information about the age and gender of injured workers, affected body region and depth of burns (free-text), industry type and size of the companies, and a brief history of the incidents (free-text). Information about the causative agents and tasks done by the injured workers were extracted from the brief history of the incidents by an occupational medicine specialist (DHK). The affected body regions and depths of burns were also extracted and coded according to the ICD-10 scheme, but some of body regions or depths of burns overlapped. For this reason, some cases were coded ‘Head & upper extremities’ for affected body region and ‘Second to third degree’ for depth of burns as shown in Table 2.

2.3.

Statistical analysis

We evaluated the distributions of the age, year of injury, affected body region, and depth of skin burns by gender, using the NHIS-NSC. Also, we estimated the hospital visit incidence and 95% confidence intervals (CIs), according to the body part and insurance type by gender. CIs of the incidences were calculated, using the ‘epitools’ package of statistical software R [14]. We assumed the chemical burn occurrences follow Poisson distributions, which is the conventional probability model for non-contagious diseases [15]. We calculated the relative risks (RRs) of the hospital visits, according to the insurance type, adjusting for age and gender using the NHIS-NSC. Poisson regression models were employed when calculating RRs and CIs. To do so, case and person-year were collated in tables by age group in 5-year intervals, gender, and insurance type. In the Poisson regression models, the number of cases was incorporated as a dependent variable, while age group, gender, and insurance type were incorporated as categorical variables, and log-transformed person-year was incorporated as an offset. A diagnostic test of the models was performed, and as a result, no significant violation of assumptions was found in the residual analyses [16]. In addition, we evaluated the distributions of the age, year of injury, affected body region, and depth of skin burns by gender using the workers’ compensation data. We also estimated incidence and 95% CIs of compensated chemical burns. To evaluate the characteristics of the compensated chemical burns, we further examined the distributions of industry type, task, and size of company by gender, and causative agents by body part (skin, eye, and internal organs).

2.4.

Ethics

This study protocol was reviewed and approved by the Institutional Review Board of Inha University Hospital (INHAUH 2016-01-011).

3.

3

Results

A total of 605 patients aged 20–59 years old in the NHIS-NSC cohort visited hospitals for chemical burns between 2009 and 2013 period (Table 1). In terms of age at hospital visit, 30–39 for males and 50–59 for females were the most frequent age categories. However, no significant difference was observed between age categories both in men and women. As for year of injury, the largest number of patients visited hospitals in 2013. Especially in males, a significant difference was observed within the year of injury (p=0.01). The eye (50.16%) was the most commonly affected body part for males, while the skin (53.45%) was the most commonly affected body part for females. For skin lesions, the hands and wrists were the most common body region both in males and females. In terms of depth of the burns, second degree burns were the most common type, then followed by first and third degrees. However, 27.7% of all cases did not report the specific depth of the burns. Meanwhile, for the workers’ compensation data, 1237 patients aged 18–80 years old were treated for chemical burns between 2009 and 2013 (Table 1). In terms of age of chemical burn, 30–39 for males and 40–49 for females were the most frequent age categories. Significant differences in age categories were observed both in men (p<0.01) and women (p<0.01). As for the year of injury, the largest number of patients visited hospitals in 2012. No significant difference in the year of injury was observed either in males or females. The skin was the most commonly affected body part for both males (78.84%) and females (68.75%). For skin lesions, the hands and wrists were the most common body region for males, while the shoulders and upper extremities were the most common body regions for females. In terms of depth of the burns, second degree burns were the most common type, followed by third and first degree burns. However, 25.77% of all cases did not report any specific depth of burns. Overall hospital visit incidence of chemical burns in the NHIS-NSC cohort was 1.96 per 10,000 person-years (95%CI: 1.80–2.12) (Table 2). The person-year for males and females in the NHIS-NSC cohort was 1,574,601 and 1,517,063 personyears, respectively. The incidences between both genders were not significantly different. Skin lesions yielded the highest incidence of chemical burns for females, but the eyes showed the highest incidence for males. As for insurance type, employee and self-employee showed greater incidences than dependents. Meanwhile, for the workers’ compensation data, the compensated chemical burn incidence was 0.17 per 10,000 person-years (95%CI: 0.16–0.18) (Table 2). Person-years were replaced with the number of workers (73,443,698) covered by the workers’ compensation system between 2009 and 2013, irrespective of age. The skin showed the highest incidence among all body parts. Due to the lack of the number of workers covered by worker’s compensation by gender, gender-specific incidence could not be calculated. Age- and gender-adjusted incidence rate ratios (RRs) by insurance type in the NHIS-NSC cohort are shown in Table 3. For men, only employee insured showed a significantly increased RR (1.40, 95%CI: 1.04–1.87) compared to dependents,

Please cite this article in press as: D.-H. Koh, et al., Incidence and characteristics of chemical burns, Burns (2016), http://dx.doi.org/ 10.1016/j.burns.2016.08.037

Characteristics

NHIS-NSC (2009–2013) Male N

Gender

Workers’ compensation (2009–2013)

Female %

315

N

%

290

Total N

Male %

605

N

Female %

965

N

%

272

Total N

%

1237

15–19 20–29 30–39 40–49 50–59 60–69 70–79 80–89

– 65 101 78 71 – – –

– 20.64 32.06 24.76 22.54 – – –

– 68 66 69 87 – – –

– 23.44 22.76 23.79 30.00 – – –

– 133 167 147 158 – – –

– 21.98 27.61 24.30 26.12 – – –

5 159 276 251 201 69 3 1

0.52 16.48 28.60 26.01 20.83 7.15 0.31 0.10

1 45 40 82 80 20 4 0

0.37 16.54 14.71 30.15 29.41 7.35 1.47 0.00

6 204 316 333 281 89 7 1

0.49 16.49 25.55 26.92 22.72 7.19 0.57 0.08

Year

2009 2010 2011 2012 2013

48 57 67 58 85

15.24 18.10 21.27 18.41 26.98

60 52 65 54 59

20.69 17.93 22.41 18.62 20.34

108 109 132 112 144

17.85 18.02 21.82 18.51 23.80

168 200 176 215 206

17.41 20.73 18.24 22.28 21.35

64 53 47 57 51

23.53 19.49 17.28 20.96 18.75

232 253 223 272 257

18.76 20.45 18.03 21.99 20.78

Region (ICD-code)

Head and neck (T20) Trunk (T21) Shoulder and upper extremities (T22) Wrist and hand (T23) Hip and lower limb (T24) Ankle and foot (T25) Multiple body regions (T29) Body region unspecified (T30) Classified according to extent of body surface involved (T32) Head and upper extremities Hand and upper extremities Foot and lower extremities Confined to eye and adnexa (T26) Respiratory tract (T27) Gastrointestinal tract (T28)

20 6 12 32 27 17 12 16 0 – – – 158 1 14

6.35 1.90 3.81 10.16 8.57 5.40 3.81 5.08 0 – – – 50.16 0.32 4.44

14 10 33 40 28 11 4 14 1 – – – 122 2 11

4.83 3.45 11.38 13.79 9.66 3.79 1.38 4.83 0.34 – – – 42.07 0.69 3.79

34 16 45 72 55 28 16 30 1 – – – 280 3 25

5.62 2.64 7.44 11.9 9.09 4.63 2.64 4.96 0.17 – – – 46.28 0.50 4.13

105 20 80 183 125 57 117 9 – 36 6 23 174 17 11

10.88 2.07 8.29 18.96 12.95 5.91 12.12 0.93 – 3.73 0.62 2.38 18.03 1.76 1.14

23 7 52 37 28 18 15 0 – 4 1 2 68 2 15

8.46 2.57 19.12 13.60 10.29 6.62 5.51 0.00 – 1.47 0.37 0.74 25.00 0.74 5.51

128 27 132 220 153 75 132 9 – 40 7 25 242 19 26

10.35 2.18 10.67 17.78 12.37 6.06 10.67 0.73 – 3.23 0.57 2.02 19.56 1.54 2.10

Depth of skin burns

First degree Second degree Second to third degree Third degree Not reported

12 79 – 11 40

8.45 55.63 – 7.75 28.17

14 87 – 11 42

9.09 56.49 – 7.14 27.27

26 166 – 22 82

8.78 56.08 – 7.43 27.7

6 332 60 152 210

0.79 43.68 7.89 20.00 27.63

6 96 15 36 34

3.21 51.34 8.02 19.25 18.18

12 428 75 188 244

1.27 45.20 7.92 19.85 25.77

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Age

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Table 1 – General characteristics of chemical burns in the National Health Insurance Service-National Sample Cohort (NHIS-NSC) and workers’ compensation data.

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4.

Internal organs, respiratory and gastrointestinal tracts; CI, confidence interval.

– 965 Total

5

while in women, both self-employed insured (1.56, 95%CI: 1.09– 2.23), and employee insured (1.52, 95%CI: 1.18–1.96) showed significantly increased RRs compared to dependents. As for workers’ compensation data, ‘Manufacture of chemicals and chemical products’, ‘Plating and anodizing of metals’, and ‘General construction’ were common industry categories for males, while, for females, ‘Food and beverage, personal service activities and business support service’ and the ‘Education’ industry category dominated (Table 4). In terms of tasks, ‘Manufacturing process, unspecified’, ‘Maintenance and repair of industrial facility’, and ‘Plating’ were common tasks involved with compensated chemical burns for males, while, for females, ‘Restaurant and cafeteria worker’ dominated, followed by ‘Laboratory’ tasks (Table 4) were common. As for the size of the company, companies hiring less than five workers showed the largest portion for males (28%), while for females, companies hiring 16–29 workers showed the largest portion (23%) (Table 4). In the workers’ compensation data, ‘Cleaning agent, unspecified’, ‘Sulfuric acid’, and ‘Chemical, unspecified’ were common causative agents for skin chemical burns, while, for eye burns, ‘Sodium hydroxide’ and ‘Cleaning agent, unspecified’ were common causative agents (Table 5). As for internal organs (respiratory and gastrointestinal tracts) burns, ‘Cleaning agent, unspecified’ was the most common causative agent (Table 5).

1237

0.12–0.14 0.03–0.04 <0.01–0.01 0.13 0.03 0.01 – – – – – – Body part Workers’ compensation

Total

Skin Eye Internal organs

760 177 28

– – –

– – –

187 68 17

947 245 45

1.80–2.12 1.96 1.70–2.14 1.91 290 315

2.00

1.79–2.23

605

1.62–2.41 2.06–2.61 1.42–1.85 1.99 2.32 1.63 104 278 223 Self-employed Employee Dependent Insurance type

65 172 78

1.78 2.31 1.67

2.46 2.33 1.60 39 106 145 1.38–2.27 1.98–2.69 1.32–2.09

1.75–3.36 1.91–2.82 1.35–1.89

0.85–1.08 0.80–1.02 0.06–0.13 0.96 0.91 0.09 297 280 28 Skin Eye Internal organs NHIS-NSC

Body part

142 158 15

0.90 1.00 0.10

1.02 0.80 0.09 155 122 13 0.76–1.06 0.85–1.17 0.05–0.16

0.87–1.20 0.67–0.96 0.05–0.15

95% CI Incidence Case

Incidence

Incidence

95% CI Case 95% CI

Case

Total Female Male Characteristics Database

Table 2 – Incidence (number of cases per 10,000 person-year) of chemical burns in the National Health Insurance Service-National Sample Cohort (NHIS-NSC) and workers’ compensation data (2009–2013).

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Discussion

Most previous studies about the incidences of chemical burns in Korea have been conducted based on the experiences at burn centers in hospitals, thus these studies only provided inpatient incidence around areas in which the hospitals were located. In the present study, we attempted to overcome the shortcomings by analyzing a nationally representative health insurance claim database which included in-and out-patient claim records for all areas in Korea. In addition, we elucidated characteristics of chemical burns using a nationwide workers’ compensation database. Chemical burns comprised 1.6% of all types of burns in a study based on a big burn center in Korea [17]. In Hong Kong, chemical burns comprised 5.45% of adult burns based on a burn center report [18]. Chemical burns accounted for up to 16.5% of burns in the 1980s in the UK [7]. As for a working population, the U.S. Bureau of Labor Statistics (BLS) reported the incidence of chemical burns in 2006 was 1 per 10,000 fulltime workers, and chemical burns comprised 0.6% of occupational injuries and illness resulting in loss of work time [2]. In the present study, our results show that the chemical burn incidence could be up to 2.13 persons per 10,000 in the general working-aged population (Table 2; 1.96 from NHIS-NSC cohort +0.176 from workers’ compensation data). In most studies, the most common place where chemical burns occurred was in industrial settings [19,20]. Incidents involving chemicals may occur throughout all the lifecycle of many chemicals from production, transportation, handling, and to disposal [19]. In a study of occupational skin disease carried out for 4000 workers in 104 companies in Greece, 5.3% of workers experienced chemical burns, and 13% of industrial

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Table 3 – The relative risk (RR) of chemical burns by insurance type in the National Health Insurance Service-National Sample Cohort (NHIS-NSC), adjusting for age (2009–2013). Insurance type

Men

Self-employed Employee Dependent

Women

Total

RR

95% CI

RR

95% CI

RR

95% CI

1.13 1.40 Ref

0.79–1.62 1.04–1.87

1.56 1.52 Ref

1.09–2.23 1.18–1.96

1.29 1.49 Ref

1.01–1.65 1.23–1.79

CI, confidence interval.

Table 4 – Chemical burns by industry, task and size of company in workers’ compensation (2009–2013). Male

Characteristics

N Industry

Agriculture Forestry Operation of fish cultivating and fish farms and services incidental to fishing Manufacture of basic iron and steel and cast of metals Manufacture of basic precious and non-ferrous metals Manufacture of cement Manufacture of ceramic ware Manufacture of chemicals and chemical products Manufacture of coke, hard-coal and lignite fuel briquettes and refined petroleum products Manufacture of concrete and non-metallic mineral products, and fabricated metal products Manufacture of electrical equipment Manufacture of electronic components, computer, radio, television and communication equipment and apparatuses Manufacture of food products Manufacture of glass and glass products Manufacture of machinery and equipment Manufacture of medicaments, perfumes and cosmetics Manufacture of precision and optical instruments, and other precision instruments Manufacture of pulp, paper and paper products Manufacture of rubber products Manufacture of textiles and apparel Manufacture of transport equipment Manufacture of wooden products of wood and cork Manufacture of leather, luggage, footwear and jewelry Plating and anodizing of metals Shipbuilding, maintenance and repair services Other manufacturing Electricity, gas, steam and air conditioning supply Cleaning of building and industrial facilities, and waste collection, disposal and materials recovery General construction Wholesale trade, retail trade, maintenance and repair services Transit and ground passenger transportation Transport of parcels Water transport and freight handling Freight trucking Support activities for transportation Warehousing Food and beverage, personal service activities, and business support service Printing and publishing activities Financial institutions, insurance and pension funding Professional, scientific and technical services Maintenance and repair services of motor vehicles and motorcycles

Female %

N

%

Total N

%

5 4 1

0.52 0.41 0.10

0 2 0

0 0.74 0

5 6 1

0.39 0.47 0.08

9 6 4 3 144 1

0.93 0.62 0.41 0.31 14.92 0.10

0 0 0 0 7 0

0 0 0 0 2.57 0

9 6 4 3 151 1

0.70 0.47 0.31 0.23 11.73 0.08

20

2.07

1

0.37

21

1.63

9 38

0.93 3.94

0 3

0 1.10

9 41

0.70 3.19

26 7 52 6 6

2.69 0.73 5.39 0.62 0.62

17 1 4 3 1

6.25 0.37 1.47 1.10 0.37

43 8 56 9 7

3.34 0.62 4.35 0.70 0.54

6 4 33 11 1 2 116 3 14 2 56

0.62 0.41 3.42 1.14 0.10 0.21 12.02 0.31 1.45 0.21 5.80

0 0 4 2 0 0 4 1 1 1 9

0 0 1.47 0.74 0 0 1.47 0.37 0.37 0.37 3.31

6 4 37 13 1 2 120 4 15 3 65

0.47 0.31 2.87 1.01 0.08 0.16 9.32 0.31 1.17 0.23 5.05

154 27 3 1 6 16 2 3 100

15.96 2.80 0.31 0.10 0.62 1.66 0.21 0.31 10.36

2 4 1 0 0 0 0 0 78

0.74 1.47 0.37 0 0 0 0 0 28.68

156 31 4 1 6 16 2 3 178

12.12 2.41 0.31 0.08 0.47 1.24 0.16 0.23 13.83

5 2 11 1

0.52 0.21 1.14 0.10

1 0 10 0

0.37 0 3.68 0

6 2 21 1

0.47 0.16 1.63 0.08

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Table 4 (continued) Male

Characteristics

Cleaning and pest control services of building and industrial facilities Golf courses and racetrack operation Public administration, defense and social security Education Human health and social work activities Extraterritorial organizations and bodies

Female

Total

N

%

N

%

39 1 0 1 3 1

4.04 0.10 0 0.10 0.31 0.10

16 0 3 77 19 0

5.88 0 1.10 28.31 6.99 0

55 1 3 78 22 1

4.27 0.08 0.23 6.06 1.71 0.08

N

%

Task

Agriculture Pesticide application Forestry Fish farm Livestock Manufacturing process, unspecified Maintenance and repair of industrial facility Dyeing Plating Painting Carrying containers in the workplace Degreasing and rust-removing Cleaning of the workplace Cleaning of roadside sign Cleaning of glasses and external walls Cleaning of hospital Cleaning of public bath and sauna Cleaning of restroom Cleaning of school Cleaning of swimming pool Car wash Waste collection, disposal and materials recovery Wastewater treatment Construction Waterproofing Retailer Loading and unloading of chemicals Door to door transport Warehouse Restaurant and cafeteria workers Hairdresser Jeweler Laboratory Laundry Snow-removing work Soap-making Vehicle maintenance and repair Working in clinics and dentistry

3 3 1 1 1 293 105 2 125 9 26 20 15 1 37 2 3 5 1 1 3 9 34 93 1 1 63 1 1 60 0 0 32 8 2 0 2 1

0.31 0.31 0.10 0.10 0.10 30.36 10.88 0.21 12.95 0.93 2.69 2.07 1.55 0.10 3.83 0.21 0.31 0.52 0.10 0.10 0.31 0.93 3.52 9.64 0.10 0.10 6.53 0.10 0.10 6.22 0 0 3.32 0.83 0.21 0 0.21 0.10

2 2 0 0 0 33 4 0 3 0 4 0 6 0 9 2 3 7 1 0 0 0 1 1 0 1 3 0 0 142 1 2 38 0 0 1 0 6

0.74 0.74 0 0 0 12.13 1.47 0 1.10 0 1.47 0 2.21 0 3.31 0.74 1.10 2.57 0.37 0 0 0 0.37 0.37 0 0.37 1.10 0 0 52.21 0.37 0.74 13.97 0 0 0.37 0 2.21

5 5 1 1 1 326 109 2 128 9 30 20 21 1 46 4 6 12 2 1 3 9 35 94 1 2 66 1 1 202 1 2 70 8 2 1 2 7

0.39 0.39 0.08 0.08 0.08 25.33 8.47 0.16 9.95 0.70 2.33 1.55 1.63 0.08 3.57 0.31 0.47 0.93 0.16 0.08 0.23 0.70 2.72 7.30 0.08 0.16 5.13 0.08 0.08 15.70 0.08 0.16 5.44 0.62 0.16 0.08 0.16 0.54

Size of company

>2000 workers 1000–1999 workers 500–999 workers 300–499 workers 200–299 workers 100–199 workers 50–99 workers 30–49 workers 16–29 workers 10–15 workers 5–9 workers <5 workers Unknown

16 7 17 16 27 52 75 81 142 99 157 274 2

1.66 0.73 1.76 1.66 2.80 5.39 7.77 8.39 14.72 10.26 16.27 28.39 0.21

6 7 7 7 7 8 21 34 63 32 27 53 0

2.21 2.57 2.57 2.57 2.57 2.94 7.72 12.50 23.16 11.76 9.93 19.49 0

22 14 24 23 34 60 96 115 205 131 184 327 2

1.78 1.13 1.94 1.86 2.75 4.85 7.76 9.30 16.57 10.59 14.87 26.43 0.16

Total

965

100

272

100

1237

100

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Table 5 – The causative agents extracted from workers’ compensation data (2009–2013). Agent

S

E

I

Agent

S

E

I

4-ter-Butylcatechol (TBC) Acetic acid Acid chemical, unspecified Acid cleaning agent Adhesive Adhesive remover Alkali chemical Alkali cleaning agent Aluminate-based cement accelerating agent Aluminum sulfate Ammonia Ammonia bifluoride Ammonium nitrate Ammonium sulfate Antiseptics Boric acid Bromic acid Bromine compounds Bromoacetyl bromide Calcium chloride Calcium hydroxide Calcium oxide Car battery fluid Cashew nut shell liquid (CNSL) Cement Chemical, unspecified Chloroform Chromic acid Cleaning agent, unspecified Cresol Cupric sulfate Deodorant Detergent Dimethyl sulfate Dimethylaminoethyl acrylate Dyeing agent Epoxy Etching agent Ethylene Ethylene diamine Fast-setting cement waterproofing agent Ferric chloride (FeCl3) Fire extinguisher fluid Fluid used for grouting Flux Gas flux

1 14 14 7 10 1 8 53 1 1 6 1 1 1 4 2 1 1 2 1 2 5 0 1 57 108 1 5 136 3 1 1 2 1 1 2 2 3 1 1 0 0 1 0 3 0

0 8 6 1 0 0 5 14 0 0 5 0 0 0 0 0 0 0 0 1 1 4 2 0 15 27 1 3 34 0 1 0 0 0 0 0 2 1 0 0 1 1 0 2 0 1

0 2 0 1 0 0 1 3 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0 0 11 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Formic acid FRP hardener Gold (18 K) testing solution Gypsum Hardener, unspecified Hydrochloric acid Hydrofluoric acid Hydrogen peroxide Iodine Lubricant Manganese solution Metam sodium Methanol Methyl ethyl ketone (MEK) Methyl metacrylate (MMA) Methylene chloride Molybdenum disulfide Nickel sulfamate Nitric acid Paint Paint remover Pesticide Phenol Phenyltrichlorosilane Phosphoric acid Phthalic anhydride Plating agent, unspecified Potassium hydroxide Reagent, unspecified Refrigerant, unspecified Sodium aluminate Sodium cyanide Sodium hydroxide Sodium hypochlorite (NaClO) Sulfuric acid Surfactant, unspecified Tetrachlorosilane (SiCl4) Tetraethylammonium hydroxide (TMAH) Thinner, unspecified Trichloroacetic acid (TCA) Trifluoroacetic acid UV coating agent Wastewater treatment agent, unspecified Waterproofing agent Wood vinegar Xylene

7 1 1 3 0 38 77 4 0 1 0 1 0 0 0 2 1 1 45 0 3 3 11 0 4 1 45 6 1 1 2 1 78 5 118 1 3 1 0 2 2 9 1 0 0 0

0 1 0 0 1 9 4 0 2 0 1 0 1 1 1 2 0 0 4 4 1 1 1 1 0 0 7 0 0 0 0 0 47 10 5 1 0 0 1 0 0 0 0 1 1 1

0 0 0 0 2 8 1 0 0 0 0 0 0 0 0 0 0 0 7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4 1 0 0 0 0 0 0 0 0 0 0 0

S, skin burns; E, eye burns; I, internal organ (respiratory, gastrointestinal tract) burns.

cleaning workers suffered chemical burns [21]. A study in Bulgaria reported that domestic chemical burns are more frequent than industrial chemical burns [22]. In the UK, a study analysed chemical burns between 1981 and 1987 and reported industrial causes as 76% of the incidences, yet, a subsequent study conducted between 2003 and 2011 reported incidence at 35% which was less than the an incidence rate of 43% for domestic chemical burns [7]. This might be due to the introduction of strict safety and heath regulations, and the shift of economic structure from a manufacturing to a service industry [7]. In the present study, the employees were at a 49% increased risk of chemical burns than dependents in the NHISNSC cohort (Table 5), which implies work-related causes

played a significant role in chemical burns in the general population. The self-employed also were at an increased risk of chemical burns but only for females, which may be due to the job characteristics for women. Typically, women who are cleaning restaurants and cafeterias including school cafeterias comprised more than half of the chemical burns for females according to workers’ compensation data (Table 4). From this result, we suspect that many women are working in small restaurants commonly run by families and they might claim for national health insurance services (NHIS) rather than going to the workers’ compensation system. These women will be a group benefiting from special attention on the prevention of chemical burns.

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Chemical burns have been reported to be more frequent in men than women [7]. In a few studies, the male to female ratio was about 3:1 for chemical burned patients [6,22,23]. However, the male:female ratio varied higher to 10:1 in a study in Iran [1]. Contrastingly, a study performed in India reported that females (54%) were more commonly injured than males, which might also be attributable to the high rate of assault (29%) and suicide (13%) [24]. In our study, the incidences of chemical burns for both males and females calculated from NHIS-NSC cohort were similar to each other in the general population (Table 4). However, regarding workers’ compensation data, chemical burns for males were more frequent than those for females (3.5:1). Because we did not obtain the information about the male to female ratio for workers covered by the workers’ compensation system, we could not calculate gender-specific incidences of compensated chemical burns exactly, yet, our results may indicate that chemical burns are also prevalent for women and chemical burns for women should not be neglected. The working age is the most common age group in which chemical burns occur [25]. In a study in China, it was reported that the working age of 15–60 years old comprised 89.2% of all chemical burn admissions [6]. In our workers’ compensation data, the working age of 20–59 years old also comprised 91.7% of all compensated chemical burns (Table 1). In terms of jobs, in a study in China, it was reported that ‘workers’ comprised 64.7% of all admissions due to chemical burns followed by farmers (13.3%) and managing clerks (5%) [6]. Chemical burns have also been frequently reported in the mining industry. The U.S. Mine Safety and Health Agency (MSHA) reported that chemical burns were the most common type of chemical-related injuries, accounting for 57% of all cases, followed by coal workers pneumoconiosis (24%) during the period 1999–2006. Eyes were the most common body part burned and acids and alkalis were the most common types of causative agents [26]. In a study in Saudi Arabia, chemical burns from car battery spillage were reported, which even caused chemical burns in children [23]. In a study in Serbia, it was reported that an explosion of car batteries comprised 8% of all eye chemical injuries [27]. From the brief history of incidents in our workers’ compensation data, a few typical exposure scenarios could be formulated. In men, workers wearing gloves with a pinhole or tear did their job using acids or alkalis and they recognized pain on their hands only after work finished and found their skin had discolored. Another scenario will be construction workers who wore boots and experienced chemical burns around the calf area when the cement mortar had overflowed into boots, or when a worker’s pants had became wet with cement containing fluids. In women, cafeteria workers who had their elbows burned while degreasing an overhead hood would be a typical scenario. Newly employed women wore gloves when they were cleaning hoods using alkali fluids and raise their hands over their shoulders. Accordingly, alkali fluid can easily run down and stagnate at the elbow area. This then leads to chemical burns in the upper extremities typically, not in the hands. This scenario implies the importance of education to prevent chemical burns. Performing laboratory tasks was also a common job type for women. For internal organ burns, cafeteria workers who swallowed alkali cleaning agents

9

mistaking them for tea or water would be a typical scenario. Adding peculiar colors, smells, and tastes into those cleaning agents will be helpful to prevent further gastrointestinal tract chemical burns. In terms of causative agents, acids and alkalis are the most common agents. In a study in China, it was reported that acid and alkali comprised 61.01% and 32.36%, respectively, of incidents [6]. In a study from Saudi Arabia, ‘cleaner’ burns are the most common etiologic agents. Incidents usually occurred at home when the cleaners were used for clogged drains and the reflux of cleaner from the drains caused injury [23]. In a burn center-based study in Iran, tar was the most common causative agent, not acids or alkalis [1]. In our workers’ compensation data, acids and alkalis were the most common causative agents. Cleaning agents especially, which are used in restaurants and cafeterias (alkali), and building cleanings (acid), were the typical agents. As for body region of skin chemical burns, a study reported that the lower limb was the most common region of chemical burns [6]. However, other studies reported that hands and wrists, or upper extremities, were the most common burn regions [1,6]. While a study in India reported that heads and necks comprised 37% of injuries, and which is the most commonly affected region, this incidence may be due to high rates of assault [24]. Use of acid and chemicals for assault, robberies, and suicide has become a big issue, especially in developing countries [28]. In our study, hands were most common body region in the NHIS-NSC cohort and workers’ compensation data, except for women in the workers’ compensation data. Women workers were most affected in their upper extremities doing a cleaning job as aforementioned. Ocular burns have been reported to comprise 15.5% of all eye injuries and 72.3% of ocular burns were reported to be work-related in German studies [29,30]. Chemical ocular burns accounted for 19.6% of eye injuries in a study in Taiwan [18]. Acids and alkalis are the most common causative agents in eye injury and alkalis were reported to be more common than acids [31]. In our study, eye burns comprise 46% of chemical burns for the NHIS-NSC cohort while the same burns comprise 20% of chemical burns for the workers’ compensation data. These variations may be due to the fact that people perceived eye injury seriously so they tend to visit hospitals immediately, whereas only some of them with severe injury went through workers’ compensation. In terms of the depth of the burns, in the burn center-based studies, third degree burns or deep injuries were the most common depth of burns [22,24]. In our study, second degree burns were the most common depth of burns both for the NHIS-NSC cohort and workers’ compensation data. First degree burns were the second most common type in the NHIS-NSC cohort, but third degree burns were the second most common type for the workers’ compensation data. This result indicates that severely injured workers are more likely to go with the workers’ compensation system, while minor burns are more likely to go the NHIS. This suspicion is also suggested by the fact that chemical burn incidence in the employed was higher than that for dependents by 0.69 per 10,000 person-year in the NHIS-NSC cohort (Table 2). However, the chemical burn incidence in workers’ compensation data was only 0.17 per

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10,000 person-year, which may imply that some work-related chemical burns were transferred out of the workers’ compensation system. Employers do not wish to hold occupational injuries among their workplace safety records because it potentially causes them some disadvantages such as labor inspector’s visits and the increase of premiums [32]. The mechanisms of chemical burns involved were through oxidation, reduction, corrosion, protoplasmic poison, by vesicants, and by desiccants [33]. Acids with a pH<2 can lead to coagulation necrosis, and alkalis with a pH>11.5 can lead to tissue injury through liquefaction necrosis. The potential hazards of weak fluoric acid in as low as 5% concentrations are often neglected as it does not cause immediate skin lesions; it may lead to skin burns after 2–3h without treatment [19]. Organic solvents dissolve the lipid membrane of cells and disrupt the cellular protein structure [33]. Chemical burns often cause serious consequences. The mortality rate due to chemical burns has been reported to be up to 13.8% [5]. Chronic exposure to strong acid mists, such as sulfuric acid, is known to even cause laryngeal cancers [34]. The ways of preventing chemical burns have been extensively discussed in previous papers [6,19]. In summary, prevention will benefit from further education of workers, managerial improvement, and governmental regulations. Primary emergency responses, including massive water irrigation, and on-site shower equipment are necessary. In the acid/alkali manufacturing industry, workers should be given regular safety education programs. The causative agents can expose all workers as well as the general population from its production, transportation, usage, and finally disposal/ recycling. For example, acid leaked from car batteries can cause chemical burns in children as well as workers [23]. Thus, environmental exposure management should not be neglected, including a phasing out of toxic ingredients from cleaning agents dispersed for home use. Managerial efforts should be also emphasized because of the unavoidable nature of occupational injury despite precautions. Governmental inspections are also important to urge companies, as well as exposed workers, to keep up with relevant standards to prevent chemical burns. In terms of the size of the company, small companies hiring less than five workers comprised 26% of all chemical burns, which indicates that the priority of prevention should be placed on workers in small scale enterprises. The NHIS-NSC database is a large-scale cohort, representing Korea population, but several limitations have been reported [10]. The most important one would be a potential bias from mis-coding of disease status. For example, ‘T265: corrosion of cornea and conjunctival sac’ can be mis-coded as non-injurious conditions such as ‘H169: non-specific keratitis’. The coding error may lead to underestimation of true incidence, but it is an inherent limitation of insurance databases. In summary, we estimated chemical burn incidence, including in- and out-patient cases in the general population, and examined the characteristics of chemical burns by analyzing workers’ compensation data. Our results would provide essential data to develop the basis of preventative schemes. Although our study is the first study estimating nationwide chemical burn incidences, more incidents not

undergoing hospitalisation are likely to happen according to Heinrich’s 1 major incident–29 minor incidents–300 non-injury incidents rules [8]. Accordingly, further preventive measures are indictated to protect people from chemical burns.

Conflict of interest The authors declare that they have no conflict of interests.

Acknowledgement This work was supported by a research fund from Catholic Kwandong University International St. Mary’s Hospital (CKURF-201601250001).

Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j. burns.2016.08.037. REFERENCES

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