Particulate air pollution and the blood

Abstract

BACKGROUND Particulate air pollution has been associated with excess deaths from, and increases in hospital admissions for, cardiovascular disease among older people. A study was undertaken to determine whether this may be a consequence of alterations in the blood, secondary to pulmonary inflammation caused by the action of fine particles on alveolar cells, by repeatedly measuring haematological factors in older people and relating them to measurements 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 of 12 samples. Estimates of individual exposure to particles of less than 10 μm 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 personal exposure and city centre measurements of PM₁₀ were investigated by analysis of covariance, adjusting for city, season, temperature, and repeated individual measurements. RESULTS Estimated personal exposure to PM₁₀ over the previous three days showed negative correlations with haemoglobin concentration, packed cell volume (PCV), and red blood cell count (p10 measurements over three days also showed negative correlations with haemoglobin and red cell count (p10 (p3 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 PM₁₀may cause sequestration of red cells in the circulation. We propose that an action of such particles either on lung endothelial cells or on erythrocytes themselves may be responsible for changing red cell adhesiveness. Peripheral sequestration of red cells offers an explanation for the observed cardiovascular effects of particulate air pollution.