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Table 2 Summary of studies investigating portable air cleaner (PAC) use and indicators of cardiovascular health

From: Portable air cleaners should be at the forefront of the public health response to landscape fire smoke

Authors (year) Type of PAC and study design Exposure, outcomea, location, and study population Main findings
Brauner et al. [16] HEPA filter
Two PACs were operated in each home for 4 days. Units were randomly operated with the filter (filtration period) and without the filter (control period) each for half the study period.
Traffic related PM2.5
Endothelial function (RHI)
Copenhagen, Denmark
Older adults aged 60–75 years; n = 45
Exposure: Indoor PM2.5 concentrations were reduced by 62%. Geometric mean indoor PM2.5 concentrations were 4.7 μg/m3 (95% confidence interval (CI): 3.9, 5.7 μg/m3) during the filtration period and 12.6 μg/m3 (95% CI: 11.2, 14.1 μg/m3) during the control period.
Health: RHI increased by 8.1% (95% CI: 0.4, 16.3%).
Allen et al. [17] HEPA filter
Two PACs were operated in each home for 14 days. Units were randomly operated with the filter (filtration period) and without the filter (control period) each for half the study period.
Wood smoke related PM2.5
Endothelial function (RHI); inflammation (CRP)
Northern British Columbia, Canada
Adults aged 20–63 years; n = 45
Exposure: Indoor PM2.5 concentrations were reduced by 59%. Mean (standard deviation) indoor PM2.5 concentrations were 4.6 (2.6) μg/m3 during the filtration period and 11.2 (6.1) μg/m3 during the control period.
Health: RHI increased by 9.4% (95% CI: 0.9, 18%) and CRP decreased by 32.6% (95% CI: 4.4, 60.9%).
Weichenthal et al. [18] Electrostatic precipitator
One PAC was operated in each home for 14 days. Units were randomly operated with the precipitating plates (filtration period) and without the plates (control period) each for half the study period.
Indoor PM2.5 (no specific source)
Blood pressure
Manitoba, Canada
Children and adults aged 11–64 years; n = 37
Exposure: Indoor PM2.5 concentrations were reduced by 52%. Mean (standard deviation) indoor PM2.5 concentrations were 30.0 (30) μg/m3 during the filtration period and 61.0 (64) μg/m3 during the control period.
Health: Systolic blood pressure decreased by 7.9 mm Hg (95% CI: −17, 0.82 mm Hg) and diastolic blood pressure decreased by 4.5 mm Hg (95% CI: −11, 2.4 mm Hg).
Karottki et al. [19] Electrostatic precipitator
Two PACs were operated in each home for 14 days. Units were randomly operated with the precipitating plates (filtration period) and without the plates (control period) each for half the study period.
Traffic related PM2.5
Endothelial function (RHI); inflammation (CRP); blood pressure
Greater Copenhagen, Denmark
Older adults aged 51–81 years; n = 48
Exposure: Indoor PM2.5 concentrations were reduced by 46% overall, but large variations in efficacy were seen within and across homes. Median (5th–95th percentile) indoor PM2.5 concentrations were 4.3 μg/m3 (0.2–12.2) during the filtration period and 8.0 μg/m3 (3.4–20.7) during the control period.
Health: No significant effects.
Chen et al. 2015 [11] Electrostatic precipitator
One PAC was operated in each room (in college dormitory) for two 48 h periods, which were separated by a 2 week washout period. Units were randomly operated with the filter (filtration period) and without the filter (control period) each for one of the 48 h periods.
Indoor PM2.5 (no specific source)
Shanghai, China
Inflammation (CRP, fibrinogen, P-selectin, MCP-1, IL-1β, TNF-α, IL-6, MPO); blood coagulation (sCD4OL, PAI-1, t-PA, D-dimer); vasoconstriction (ET-1, ACE); blood pressure
College students with a mean (standard deviation) age of 23 (2) years; n = 35
Exposure: Indoor PM2.5 concentrations were reduced by 57%. Mean (SD) indoor PM2.5 concentrations were 41.3 (17.6) μg/m3 during the filtration period and 96.2 (25.8) μg/m3 during the control period.
Health: Geometric mean concentrations of several markers of inflammation and coagulation were reduced: MCP-1 by 17.5% (95% CI: 5.5, 30.8%), IL-1β by 68.1% (95% CI: 44.3, 81.7%), MPO by 32.8% (95% CI: 5.3, 67.5%), and sCD4OL by 64.9% (95% CI: 30.3, 82.3%). Geometric mean systolic and diastolic blood pressure decreased by 2.7% (95% CI: 0.4, 5.1%) and 4.8% (95% CI: 1.2, 8.5%), respectively.
Kajbafzadeh et al. [20] HEPA filter
Two PACs were operated in each home for 14 days. Units were randomly operated with the filter (filtration period) and without the filter (control period) each for half the study period.
Wood smoke or traffic-related PM2.5
Endothelial function (RHI); inflammation (CRP, IL-6)
Greater Vancouver area, Canada
Adults aged 19–72 years; n = 83
Exposure: Indoor PM2.5 concentrations were reduced by 40%. Mean (standard deviation) indoor PM2.5 concentrations were 4.3 (3.7) μg/m3 during the filtration period and 7.1 (6.1) μg/m3 during the control period.
Health: No significant effects.
Padro-Martinez et al. [21] HEPA filter (window unit)
Two PACs were operated in each home for 42 days. Units were randomly operated with the filter (filtration period) and without the filter (control period) each for half the study period.
Traffic-related ultrafine particles (< 100 nm)
Inflammation (IL-6, CRP, fibrinogen, TNF-RII); blood pressure
Somerville, Massachusetts, United States
Older adults with mean (standard) age of 53.6 (9.2) years; n = 20
Exposure: Particle counts were reduced by 45% (ranged from 0 to 68%).
Health: IL-6 concentrations were on average 49.6% (95% CI: 5.90, 93.3%) lower during the control period compared with the filtration period.
  1. a RHI reactive hyperemia index, CRP c-reactive protein, MCP monocyte chemoattractant protein, IL interleukin, TNF tumor necrosis factor, MPO myeloperoxidase, sCD40L soluble CD40 ligand, PAI plasminogen activator inhibitor, t-PA tissue plasminogen activator, ET-1 endothelin-1, ACE angiotensin-converting enzyme