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Table 1 Characteristics of children attending school in a low and a high pollution urban area

From: Blood pressure and particulate air pollution in schoolchildren of Lahore, Pakistan

Characteristics Low Pollution School (n=73) High Pollution School (n=93) P-value
Male sex - no. (%) 46 (63%) 46 (49.4%)  
Age - yr 10.0 (8.0-11.0) 10.0 (9.0-11.0) 0.2
Height - cm 134 (125–143) 134 (130–138) 0.9 0.9
Weight - kg 27.0 (22.0-34.0) 27.0 (25.0-31.0) 0.9
BMI - kg/m2 15.3 (14.1-16.4) 15.3 (14.4-17.1) 0.9
Passive smoking 22 (30%) 34 (36%) 0.3
Socio-economic class§    0.001
Low 7 (10%) 31 (34%)  
Middle 24 (33%) 22 (24%)  
High 41 (57%) 39 (42%)  
Outdoor PM1 - μg/m3 7.3 (5.3) 58.2 (9.6) <0.0001
Outdoor PM2.5 - μg/m3 28.5 (10.3) 183.0 (30.2) <0.0001
Outdoor PM10 - μg/m3 223.0 (93.5) 728.6 (53.5) <0.0001
Indoor PM1 - μg/m3 8.4 (5.5) 52.7 (12.1) <0.0001
Indoor PM2.5 - μg/m3 29.1 (15.1) 163.0 (61.6) <0.0001
Indoor PM10 - μg/m3 222.9 (119.4) 590.7 (219.4) <0.0001
Outdoor temperature - °C 15.5 (3.3) 14.9 (4.5) 0.4
Relative humidity - % 58.4 (16.4) 67.1 (18.5) 0.001
  1. The data is mentioned as median (25th - 75th percentile), number (%), or mean (standard deviation) § according to paternal educational level (no information for one participant in each group). Particulate Matter (PM) was measured continuously with Aerocet 531 device during the previous 24 hours (outdoor) or between 10 and 11 am on the day of examination (indoor); corresponding averages were calculated for the different fractions, i.e. particles with diameter below 1 μm (PM1), 2.5 μm (PM2.5) and 10 μm (PM10). Values of PM were excluded when humidity was > 80% (4 days, high pollution school).