Ultrafine Particle Concentrations in a Hospital

Abstract

Ultrafine particles (UFP) may contribute to the morbidity and mortality associated with exposure to ambient particles, but few data are available on ultrafine particle numbers in indoor air, where susceptible subjects spend most of their time. We measured particle number, UFP size distribution, and total suspended particulate (JSP) mass in three locations: (I) a medical floor in a large tertiary care hospital, (2) outdoor air above a construction site outside the hospital, and (3) an environmental exposure chamber with purification of intake air. Mass and number concentrations were recorded continuously in each location over 70-110 h. Mean ± SD particle (p) numbers were 3.63 ± 1.l5 } 10(3) p/cm(3) in the hospital, 3.05 ± 6.65 } 10(4) p/cm(3) outside, and 5.86 ± 2.11 } 10(2) p/cm(3) in the environmental chamber. In the hospital, particle number and mass declined during the evening hours when the unit was less active, with the particle number as low as 1.15 } 10(3) p/cm(3). Particle numbers peaked (2.78 } 10(4) p/cm(3)) in the morning hours when activity on the unit was the most intense. "Spikes" in fine particle number were often not accompanied by increases in TSP mass. In the hospital, a distinct population of ultrafine particles (median diameter approximately 23 nm) was observed during the lunch hour, suggesting a change in particle source during this time. Outdoor fine particle numbers above the construction site were highly variable, reaching peaks of greater than 1.7 } 10(6) p/cm(3). These data suggest that, in the indoor environment, particle numbers and size distribution vary with intensity and type of local activity, and significant peaks in particle number are not detected with daily averages. Monitoring of particle mass may be an inaccurate measure of exposure to ultrafine particles indoors.

Assessment of Indoor-Outdoor Particulate Matter Air Pollution: A Review

“…The results of I/O ratios varied in the literature from values tending to zero in modern mechanically-ventilated buildings with an absence of indoor activities to values over 10 in the occupational sector or for residential buildings with intense indoor activity and smoking in territories with relatively low outdoor concentrations [10,37,42]. This wide range is consistently influenced by resuspension, air exchange, and the deposition velocity of particles.…”

“…Concentrations vary from low values (<10 3 particles/cm 3 ) in particularly clean indoor environments [37] to high values (>10 6 particles/cm 3 ) in the presence of intense indoor sources of such particles [67]. Diapouli et al [68] report higher UFP mean concentrations outdoors (32,000 ± 14,200 particles/cm 3 ) rather than indoors (24,000 ± 17,900 particles/cm 3 ), with a maximum indoor mean value found in a library with a carpet-covered floor and a smoking office (both ≈52,000 particles/cm 3 ).…”

“…In the absence of intense indoor sources, studies show a general trend of higher outdoor concentrations rather than indoor values [8,36,37]. Furthermore, spatial and temporal variability of outdoor PM could significantly affect the relation between I-O concentrations [38].…”

Systemic and cardiovascular effects of airway injury and inflammation: ultrafine particle exposure in humans.

“…McMurry (22) measured UFP numbers exceeding 1,000,000/cm 3 in Atlanta, Georgia. We have observed peak particle numbers exceeding 1,700,000/cm 3 above a construction site outside an acute care hospital (23).…”

Overview of ultrafine particles and human health

“…Normal household concentrations average ~10,000 cm -3 [5], with hospital concentrations about half this [6]. Cooking with gas can cause UP numbers to rise two or threefold indoors, but numbers decrease and size increases within minutes after emission [7].…”