Particulate air pollution and the blood

Background-Particulate air pollution has been associated with excess deaths from, and increases in hospital admissions for, cardiovascular disease amo ng older people. A study was undertaken to determine whether this may be a consequence of alterations in the blood, secondary to pulmonary inflammatio n caused by the action of fine particles on alveolar cells, by repeatedly m easuring haematological factors in older people and relating them to measur ements of exposure to airborne particles. Methods-One hundred and twelve individuals aged 60+ years in two UK cities provided repeated blood samples over 18 months, 108 providing the maximum o f 12 samples. Estimates of individual exposure to particles of less than 10 mu m diameter (PM10), derived from a mathematical model based on activity diaries and comparative measurements of PM10 at multiple sites and during a variety of activities, were made for each three day period prior to blood sampling. The relationships between blood values and estimates of both pers onal exposure and city centre measurements of PM10 were investigated by ana lysis of covariance, adjusting for city, season, temperature, and repeated individual measurements. Results-Estimated personal exposure to PM10 over the previous three days sh owed negative correlations with haemoglobin concentration, packed cell volu me (PCV), and red blood cell count (p<0.001), and with platelets and factor VII levels (p<0.05). The changes in red eel indices persisted after adjust ment for plasma albumin in a sample of 60 of the subjects. City centre PM10 measurements over three days also showed negative correlations with haemog lobin and red cell count (p<0.001) and with PCV and fibrinogen (p<0.05), th e relationship with haemoglobin persisting after adjustment for albumin. C reactive protein levels showed a positive association with city centre meas urements of PM10 (p<0.01). Based on a linear relationship, the estimated ch ange in haemoglobin associated with an alteration in particle concentration of 100 mu g/m(3) is estimated to have been 0.44 g/dl (95% CI 0.62 to 0.26) for personal PM10 and 0.73 g/dl (95% CI 1.11 to 0.36) for city centre PM10 measurements. Conclusions-This investigation is the first to estimate personal exposures to PM10 and to demonstrate associations between haematological indices and air pollution. The changes in haemoglobin adjusted for albumin suggest that inhalation of some component of PM10 may cause sequestration of red cells in the circulation. We propose that an action of such particles either on l ung endothelial cells or on erythrocytes themselves may be responsible for changing red cell adhesiveness. Peripheral sequestration of red cells offer s an explanation for the observed cardiovascular effects of particulate air pollution.