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 (PM 10 ), derived from a mathematical model based on activity diaries and comparative measurements of PM 10 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 PM 10 were investigated by analysis of covariance, adjusting for city, season, temperature, and repeated individual measurements. Results-Estimated personal exposure to PM 10 over the previous three days showed negative correlations with haemoglobin concentration, packed cell volume (PCV), and red blood cell count (p<0.001), and with platelets and factor VII levels (p<0.05). The changes in red cell indices persisted after adjustment for plasma albumin in a sample of 60 of the subjects. City centre PM 10 measurements over three days also showed negative correlations with haemoglobin and red cell count (p<0.001) and with PCV and fibrinogen (p<0.05), the relationship with haemoglobin persisting after adjustment for albumin. C reactive protein levels showed a positive association with city centre measurements of PM 10 (p<0.01). Based on a linear relationship, the estimated change in haemoglobin associated with an alteration in particle concentration of 100 µg/m 3 is estimated to have been 0.44 g/ dl (95% CI 0.62 to 0.26) for personal PM 10 and 0.73 g/dl (95% CI 1.11 to 0.36) for city centre PM 10 measurements. Conclusions-This investigation is the first to estimate personal exposures to PM 10 and to demonstrate associations between haematological indices and air pollution. The changes in haemoglobin adjusted for albumin suggest that inhalation of some component of PM 10 may 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 oVers an explanation for the observed cardiovascular eVects of particulate air pollution.

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Objectives-Sewer workers are used to unpleasant smells, but may be required to investigate unusual ones. Twenty six men were involved in investigation of episodes of such a smell after neighbourhood complaints over several weeks. Methods-Workers exposed to the smell were investigated by clinical follow up, lung function tests, and measurement of pituitary function. Results-14 of the 26 developed subacute symptoms including sore throat, cough, chest tightness, breathlessness, thirst, sweating, irritability, and loss of libido. Severity of symptoms seemed to be dose related. Minor symptoms resolved over several weeks but those more seriously affected have shown deteriorating respiratory symptoms and lung function and remain unable to work a year after the incident. In one, evidence of mild cranial diabetes insipidus was found. Analysis of gas from the sewer showed the presence of a mixture of thiols and sulphides, known to be highly odorous and not normally found in sewers. The source remains unknown. Conclusions-Several of these men seem to have developed delayed airways disease and disturbances of hypothalamic fimction. Such an outcome has not to our knowledge been described before. Despite the presence of the smell, standard safety gas detection equipment used to ensure the sewer was safe to enter failed to indicate the presence of a hazard. Protection against such incidents can only be provided by the use of positive pressure breathing apparatus. (Occup Environ Med 1997;54:277-280)