Vascular Responses Among Adults Four Years Post Exposure to 6 Weeks of Smoke from the Hazelwood Coal Mine Fire

Figures & data

Table 1 Demographic and Clinical Profile of the Study Sample (N=387) Across Exposure Levels

Characteristic	Exposure Level				p value
	Unexposed N=162	Low Exposure N=78	Medium Exposure N=73	High Exposure N=74
Mean daily mine fire-related PM2.5 exposure µg/m^3, mean (SD)	0.09 (0.50)	6.25 (1.80)	11.2 (1.60)	28.6 (11.1)
Peak daily mine fire-related PM2.5 exposure µg/m^3, mean (SD)	5.52 (27.5)	87.5 (22.5)	143 (52.3)	421 (230)
Framingham Risk Score %, mean (SD)	0.25 (0.10)	0.28 (0.20)	0.25 (0.10)	0.26 (0.20)	0.37
Age group, n
55–64 years	35 (30%)	13 (19%)	15 (24%)	15 (25%)	0.64
65–74 years	75 (37%)	41 (50%)	31 (40%)	35 (41%)
75+ years	52 (33%)	24 (31%)	27 (36%)	24 (34%)
Gender (male), n	92 (57%)	49 (62%)	41 (54%)	42 (57%)	0.78
Ethnicity (Caucasian/White), n	157 (99%)	76 (99%)	69 (95%)	74 (100%)	0.031
Employment status, n
Employed	41 (29%)	12 (17%)	8 (14%)	12 (19%)	0.19
Retired	111 (66%)	59 (73%)	58 (78%)	56 (72%)
Other	8 (5%)	7 (10%)	7 (9%)	6 (9%)
Highest educational qualification, n
Secondary up to year 10	55 (33%)	32 (40%)	31 (41%)	26 (36%)	0.44
Secondary year 11–12	33 (21%)	12 (15%)	14 (20%)	10 (14%)
Certificate (trade/ apprenticeship/technicians)	55 (35%)	27 (36%)	23 (32%)	24 (30%)
University or other Tertiary degree	18 (11%)	7 (9%)	5 (8%)	14 (20%)
Body Mass Index, n
Underweight/Normal (BMI<25kg/m^2)	40 (24%)	10 (16%)	14 (19%)	12 (18%)	0.34
Overweight (25≤BMI<30kg/m^2)	57 (37%)	21 (28%)	29 (41%)	26 (37%)
Obese (BMI≥30kg/m^2)	65 (39%)	47 (56%)	30 (41%)	36 (45%)
Smoking status, n
Non-smoker	86 (54%)	31 (39%)	37 (51%)	30 (42%)	0.029
Ex-smoker	68 (41%)	35 (44%)	33 (45%)	36 (46%)
Current smoker	8 (4%)	12 (16%)	3 (4%)	8 (12%)
Alcohol consumption, n
Non-drinker	37 (23%)	24 (30%)	16 (20%)	20 (27%)	0.21
Low risk	50 (31%)	20 (24%)	33 (45%)	27 (35%)
High risk	74 (46%)	34 (47%)	24 (35%)	27 (38%)
Limited physical activity, n	63 (40%)	36 (43%)	41 (58%)	47 (62%)	0.005
Occupational exposure, n	79 (48%)	47 (60%)	39 (49%)	34 (46%)	0.33
Past medical history, n
Cardiovascular disease	80 (45%)	35 (37%)	35 (41%)	38 (45%)	0.67
Diabetes	34 (19%)	26 (29%)	17 (23%)	23 (29%)	0.25
Hypertension	126 (77%)	66 (82%)	62 (84%)	63 (84%)	0.45
High cholesterol	22 (15%)	7 (9%)	11 (17%)	4 (4%)	0.08
Medications, n
Blood pressure lowering medications	99 (60%)	58 (70%)	50 (67%)	54 (72%)	0.28
Diabetes medications	18 (11%)	12 (13%)	14 (20%)	16 (19%)	0.28
Anti-inflammatory	12 (7%)	11 (15%)	3 (4%)	7 (9%)	0.15
Aspirin	12 (6%)	8 (9%)	14 (18%)	15 (17%)	0.010
Lipid modifying agents	63 (37%)	40 (49%)	33 (43%)	49 (65%)	0.002
Family history of heart attack or stroke, n	37 (21%)	18 (24%)	17 (24%)	19 (26%)	0.86

Notes: p values in bold are smaller than 0.05.

Abbreviations: PM_2.5, fine particulate matter with an aerodynamic diameter <2.5µm; SD, standard deviation; BMI, body mass index.

Table 2 Crude Comparison of Study Outcomes Between Unexposed, Low, Medium and High Exposure Levels

Outcome variables	Exposure Level				p value
	Unexposed N=162	Low Exposure N=78	Medium Exposure N=73	High Exposure N=74
	Mean (SD)	Mean (SD)	Mean (SD)	Mean (SD)
Average baseline diameter of brachial artery (mm)	0.48 (0.10)	0.48 (0.10)	0.47 (0.10)	0.46 (0.10)	0.56
Peak brachial artery diameter (mm)	0.49 (0.10)	0.50 (0.10)	0.49 (0.10)	0.48 (0.10)	0.50
FMD (mm)	0.018 (0.001)	0.019 (0.001)	0.018 (0.001)	0.018 (0.001)	0.86
FMD (%)	3.98 (2.70)	4.02 (2.50)	4.06 (2.50)	4.09 (2.70)	0.99
High sensitivity C-Reactive Protein level (mg/L)	3.19 (4.80)	3.54 (3.60)	3.75 (5.90)	2.78 (2.90)	0.46
	n (%)	n (%)	n (%)	n (%)
Time to peak diameter					0.002
Peak within 30s	57 (36%)	11 (13%)	15 (22%)	17 (23%)
Peak between 30 and 60s	67 (43%)	33 (44%)	26 (36%)	22 (34%)
Peak between 60 and 90s	17 (10%)	18 (25%)	18 (26%)	22 (31%)
Peak after 90s	6 (4%)	8 (12%)	7 (10%)	5 (5%)
No response within 180s	12 (7%)	6 (7%)	6 (7%)	6 (7%)
ECG evidence of underlying ischaemic heart disease	21 (15%)	14 (21%)	15 (29%)	8 (12%)	0.11

Notes: p values in bold are smaller than 0.05.

Abbreviations: FMD, flow mediated dilatation; ECG, electrocardiogram.

Figure 1 Comparison of FMD (%) distribution (A) between Morwell and Sale, and (B) between exposure levels.

Note: Statistical weighting not applied.

Figure 2 Comparison of time to peak diameter distribution (A) between Morwell and Sale and (B) between exposure groups.

Note: Statistical weighting not applied.

Table 3 Potential Predictive Factors for Flow Mediated Dilatation and Time to Peak Diameter

Predictors	Flow Mediated Dilatation (%)^a		Time to Peak Diameter^b
	Coef (95% CI)	p value	OR (95% CI)	p value
Mine fire-related daily PM2.5 (per 10 µg/m^3)	0.04 (−0.19, 0.26)	0.76	0.94 (0.77, 1.13)	0.49
Lived in Morwell	−0.11 (−0.74, 0.51)	0.72	2.71 (1.56, 4.69)	<0.001
Age (per 10 years)	−0.05 (−0.46, 0.36)	0.81	1.13 (0.81, 1.59)	0.47
Male	2.12 (1.12, 3.12)	<0.001	0.82 (0.40, 1.66)	0.57
Certificate, University or other Tertiary Institute degree	−0.05 (−0.58, 0.48)	0.85	1.53 (1.03, 2.26)	0.03
Employed	−0.89 (−1.56, −0.22)	0.009	0.83 (0.50, 1.38)	0.47
BMI	0.05 (−0.01, 0.10)	0.09	1.00 (0.95, 1.04)	0.91
Alcohol consumption
Non-drinker	Ref		Ref
Low risk (AUDIT-C score: Females 1–2, Males 1–3)	−0.41 (−1.14, 0.32)	0.27	0.88 (0.50, 1.55)	0.66
High risk (AUDIT-C score: Females ≥ 3, Males ≥ 4)	−0.30 (−1.05, 0.45)	0.43	1.08 (0.64, 1.85)	0.77
Smoking status
Non-smoker	Ref		Ref
Ex-smoker	−0.92 (−1.44, −0.40)	<0.001	0.71 (0.46, 1.09)	0.11
Current smoker	0.15 (−1.04, 1.34)	0.80	2.55 (1.39, 4.66)	0.002
Framingham Risk Score %	−1.52 (−3.71, 0.67)	0.17	0.35 (0.06, 2.05)	0.25
Family history of heart attack or stroke	0.34 (−0.23, 0.92)	0.24	1.19 (0.76, 1.86)	0.44
Average baseline diameter of brachial artery (mm)	−17.05 (−21.9, −12.2)	<0.001	1.41 (0.03, 57.35)	0.86
History of cardiovascular disease	−0.24 (−0.72, 0.24)	0.33	1.02 (0.65, 1.59)	0.94
Occupational exposure	−0.32 (−0.84, 0.20)	0.22	0.87 (0.58, 1.30)	0.49
Taking aspirin	−0.07 (−0.79, 0.65)	0.84	0.72 (0.39, 1.34)	0.30
Lipid modifying agents	−0.33 (−0.84, 0.17)	0.20	1.18 (0.79, 1.77)	0.43
Vitamin supplements within 4 hours or moderate to vigorous physical within 48 hours prior to FMD measurement	−0.15 (−0.68, 0.37)	0.56	0.77 (0.49, 1.21)	0.26
A meal, a cigarette, alcohol or coffee within 4 hours prior to FMD measurement	−0.04 (−0.89, 0.81)	0.93	0.89 (0.51, 1.53)	0.67

Notes: p values in bold are smaller than 0.05. ^aMultivariable linear regression model (weighted and imputed) was used to evaluate associations between predictors and FMD% controlling for all listed confounding factors. ^b Ordinal logistic regression model (weighted and imputed) was used to evaluate associations between predictors and time to peak FMD, controlling for all listed confounding factors.

Abbreviations: PM_2.5, fine particulate matter with an aerodynamic diameter <2.5µm; SD, standard deviation; BMI, body mass index.