Ethane

Epidemiological data

Administrative data

Endpoint:

epidemiological data

Type of information:

other: epidemiological study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

n/a

Data source

Reference

Reference Type:

publication

Title:

Airflow obstruction among street vendors who refill cigarette lighters with liquefied petroleum gas

Author:

Moitra, S., Blanc, P.D. and Brashier, B.B.

Year:

2014

Bibliographic source:

The International Journal of Tuberculosis and Lung Disease, 18(9), pp.1126-1131.

Materials and methods

Study type:

cross sectional study

Endpoint addressed:

other: Respiratory symptoms and lung function

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Liquified petroleum gase (LPG) exposed workers and non-exposed controls were assessed for respiratory symptoms and lung function.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Butane

EC Number:

203-448-7

EC Name:

Butane

Cas Number:

106-97-8

Molecular formula:

C4H10

IUPAC Name:

butane

Constituent 2

Reference substance name:

Propane

EC Number:

200-827-9

EC Name:

Propane

Cas Number:

74-98-6

Molecular formula:

C3H8

IUPAC Name:

propane

Test material form:

gas

Details on test material:

Butane/propane admixed Liquified petroleum gas used for cigarette lighter refilling

Specific details on test material used for the study:

n/a

Method

Type of population:

occupational

Ethical approval:

confirmed and informed consent free of coercion received

Details on study design:

113 LPG exposed male workers, who manually refill cigarette lighters with LPG for at least five years, and 79 male non-exposed controls, e.g.garment or food vendors located in the same or adjacent location of LPG-lighter refilling stations, were examined for respiratory symptoms and lung function. All study subjects were from two Indian townships. The mean age of LPG exposed workers was 41.9 +/- 9.9 years and of the controls 40.8+/-7.2 years. Subjects who were receiving antibiotic treatment, underwent an active medical condition in the last 12 months or were unable to perform spirometry were excluded from the study.
LPG exposed workers were asked to keep records of the number of cigarette lighters they refilled daily for one week in order to calculate daily LPG use which was used as a measure of exposure. The subjects were also interviewed for the European Community Respiratory Health Survey (ECRHS-II) questionnaire. The reported symptoms were categorised into the following groups: 1) current or chronic cough; 2) acute or chronic wheezing or whistling in the chest; 3) production phlegm; 4) difficulty breathing; 5) nasal problems (irritation in nose, dryness or stuffy nose, sneezing, runny nose or nasal congestion); 6) eye problems; 7) nasal problems with watery eyes; and 8) skin symptoms, such as dryness, rash or irritation.
The lung function was measured using a computerised spirometer (Maestros Mediline Systems Limited, Navi Mumbai, India). The forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), FEV1/FVC ratio and forced expiratory flow for 25–75% of FVC (FEF25–75) were measured away from locations that could produce environmental interference.

Exposure assessment:

estimated

Details on exposure:

LPG exposed workers were asked to keep records of the number of cigarette lighters they refilled daily for one week in order to calculate median daily LPG use which was used as a measure of exposure.

Statistical methods:

For group-wise comparison Mann-Whitney test was used for continuous data (age and height) and chi squared test was used for categorical data (e.g. smoking). The subjects were stratified into more or less exposed subcategories based on the median value of the daily amount of LPG exposure. Chi Squared test was used to compare the prevalence of respiratory symptoms between the subcategories as well as between the exposed and control subjects. The lung function differences were compared susing Mann-Whitney test.multiple linear regression analysis was performed within the exposure stratum to test the associations between LPG use as a continuous independent variable and each measure of lung function as the dependent outcome, in separate models for each. These multivariate models included the potential confounders of age, height and smoking status for raw values and smoking alone for age- and height-adjusted predicted values. We further analysed FEF25–75 stratified by the presence or absence of any respiratory symptom. All analyses were performed using SPSS V.20.

Results and discussion

Results:

The total, more and less exposed group daily LPG exposure ranged from 25 to 100 mL (Table 1). The characteristics of the exposed and control study participants were similar, except for age (Table 2).

The prevalence of respiratory symptoms was almost double among LPG-exposed workers compared to controls, 81% vs 45% (Table 3). Prevalence of all individual symptoms (table 3), except for throat clearing and cough, were significantly higher in exposed workers. However, there was no statistical difference in the prevalence of respiratory symptoms between more and less LPG-exposed workers.

The lung functions measured by spirometer were all lower in exposed workers (Table 4). FEV1 (I), FEV1 (%P), FEV1/FVC, FEF25-75 (I.sec-1) and FEF25-75 (%P) were statistically lower in exposed worker compared to controls. Additionally, there was a significant reduction in FEV1, FVC and FEF25–75 in the more compared to the less LPG-exposed workers. There was a strong LPG-associated negative exposure response for all lung function variables, with the exception of FEV1/FVC ratio (Table 5).

Confounding factors:

Occupation, non-occupational environmental exposure to LPG and other pollutants/respiratory irritants, second hand smoke, sex, socio-economic status

Strengths and weaknesses:

Strengths: large sample size, LPG exposure categorised into higher and lower.
Weaknesses: males subjects only, cross-sectional design as it cannot be determined whether the changes are progression over time, lung function testing was done at different times of the day, the lung functions used (specific for India) were not recent, study design did not allow wasted LPG during cigarette lighter refilling to be measured so that the wasted LPG that contributes to worker exposure could not be determined.

Any other information on results incl. tables

Table 1 Total quantity of LPG used to fill lighters each day*

	LPG use, mL per day
Exposure category (sample n)	Median	Range
Total exposure (n=113)	50	25 -100
More exposed (n=67)	75	50 -100
Less exposed (n=46)	30	25 - 45

*For 21 respondents, the number of lighters reported as being filled (presuming 3 mL/lighter) yielded a median value of 50 ml. Wasted (non-filled) LPG could not be measured (see Methods).

Table 2 Baseline characteristics for 192 study participants* by LPG exposure status

				LPG exposed stratified by exposure level
Parameters	Controls (n=79)	All exposed (n=113)	P value**	Less (n=46)	More (n=67)	P value **
Age, years, mean +SD	41.99 + 9.9	40.8 + 7.2	0.27	41.2 + 6.9	40.5+7.4	0..45
Height, m,  mean + SD	1.75  + 0.05	1.74 + 0.05	0.26	1.74  + 0.05	1.74  + 0.05	0.71
Ever smoker, n (%)	30 (38.9)	34 (31.4)	0.32	14 (30.4)	20 (29.8)	0.95

* All participants were male

** Based on the Mann-Whitney U test for age and height and the v2 test for smoking status.

SD=standard deviation

Table 3 Prevalence of respiratory tract and dermal symptoms by LPG exposure status*

				LPG exposure strata
Symtpoms	Controls (n=79) n (%)	All exposed (n=113) n (%)	P value	Les (n=46) n (%)	More (n=67) n (%)	P value
Any respiratory tract symptom	36 (45.6)	93 (81.4)	<0.01	36 (78.2)	57 (85.0)	0.49
Wheezing or whistling in chest	10 (12.7)	43 (38.0)	<0.01	14 (30.4)	29 (43.3)	0.24
Phlegm	12 (15.2)	46 (40.7)	<0.01	18 (39.1)	28 (41.8)	0.93
Persistent cough	8 (10.1)	29. (25.7)	0.01	10 (21.7)	19 (28.4)	0.57
Difficulty breathing	8 (10.1)	28 (24.8)	0.02	9 (19.6)	19 (28.4)	0.40
Chest tightness	6 (7.6)	21 (18.6)	0.05	7 (15.2)	14 (20.9)	0.61
Frequent throat clearing	22 (27.8)	24 (21.2)	0.38 8 )17.4)	8 (17.4)	16 (23.9)	0.55
Rhinitis or nasal irritation	5 (6.3)	24 (21.2)	0.01	8 (7.14)	16 (23.9)	0.55
Skin irritation	11 (13.9)	51 (45.1)	<0.01	17 (36.9)	34 (50.7)	0.21

Table 4 Comparison of lung function between the controls and the exposed and for the exposed within the LPG exposure subcategories*

	Controls vs. all exposd			Within LPG exposure strata
	Controls (n=79) mean+SD (range)	All exposed (n=113) mean + SD (range)	P value	Less exposed (n=46) mean + SD (range)	More exposed (n=67) mean + SD (range)	P value
FVC (l)	3.1160.36 (2.31–4.32)	2.9960.28 (2.19–3.82)	0.14	3.0760.27 (2.19–3.82)	2.9360.27 (2.19–3.41)	0.02
FVC (%P)	82.966.96 (69.6–95.6)	79.967.2 (60.9–99.5)	0.02	81.8966.00 (64.1–94.1)	78.6067.70 (60.9–99.5)	0.01
FEV1 (l)	2.5560.39 (1.63–3.73)	2.2660.32 (1.46–2.74)	0.01	2.3560.30 (1.63–2.74)	2.1960.33 (1.46–2.74)	0.01
FEV1(%P)	82.3568.67 (63.8–97.6)	73.25610.35 (47.3–97.5)	0.01	76.2769.44 (47.3–90.6)	71.18610.50 (48.3–97.5)	0.01
FEV1/FVC	0.8260.07 (0.65–0.94)	0.7660.08 (0.51–0.93)	0.01	0.7760.08 (0.51–0.89)	0.7560.09 (0.52–0.93)	0.21
FEF25–75 (l.sec1)	2.7960.36 (2.00–3.73)	2.3860.36 (1.24–3.22)	0.01	2.5860.29 (1.82–3.22)	2.2560.33 (1.24–2.79)	0.01
FEF25–76 (%P)	86.0568.40 (63.0–109.9)	72.89611.52 (38.1–101.7)	0.01	79.2169.77 (59.2–101.7)	68.56610.63 (38.1–87.5)	0.01

* Comparisons made using the Mann-Whitney test.

LPG¼liquefied petroleum gas; FVC¼forced vital capacity; %P¼per cent predicted; FEV1¼forced expiratory volume in 1 second; FEF25–75¼forced expiratory flow

25–75% of FVC.

Table 5 Effect ( β) of LPG exposure on lung function in exposed participants (n=113)*

	Relationship between LPG and lung function**
Variables	β + SE	95%CI	P value
FVC, l	-0.004 ± 0.001	-0.005 to -0.002	<0.01
FVC % predicted	-0.093 ± 0.027	-0.15 to -0.04	<0.01
FEV1, l	-0.004 ± 0.001	0.006 to 0.002	0.01
FEV1 % predicted	-0.14 ± 0.04	-0.021 to -0.06	0.01
FEV1/FVC	-5x10-4 ± 3x10-4	-0.001 to 2x10-4	0.19
FEF25–75 l/sec1	-0.009 ± 0.001	'-0.011 to -0.007	<0.01
FEF25–75 % predicted	-0.28 ± 0.04	-0.35 to -0.21	<0.01

*LPG effct expressed per mL exposure

**All models of raw lung function were adjusted for height, age and smoking; models of % predicted adjusted for smoking only.LPG¼liquefied petroleum gas; SE¼standard error; CI¼confidence interval; FVC¼forced vital capacity; FEV1¼forced expiratory volume in 1 second; FEF25–75¼

forced expiratory flow of 25–75% of FVC.

Applicant's summary and conclusion

Conclusions:

LPG-exposed workers showed more prevalent respiratory symptoms and a decline in lung function when compared to non-exposed controls.

Executive summary:

In order to evaluate the effects of LPG exposure on the respiratory system, 113 LPG exposed workers and 79 non-exposed controls were assessed for respiratory symptoms and lung function. The results showed LPG-exposed workers showed more prevalent respiratory symptoms and a decline in lung function. Prevalence of wheezing or whistling in chest, phlegm, persistent cough, difficulty breathing, chest tightness and rhinitis or nasal irritation were all significantly higher in the exposed workers. However, there was no statistical difference in the prevalence of respiratory symptoms between more and less LPG-exposed workers. Additionally, the forced expiratory volume in 1 second (FEV1) measures were statistically lower in exposed worker compared to controls.