Pete Moore

New evidence links air pollution with lung cancer

R of a study of Seventh-Day Adventists living in California, USA, give the first indication that long-term exposure to atmospheric particles of less than 10 m in diameter (PM10s) can increase lung-cancer risk in men. Researchers monitored 6338 non-smoking, non-Hispanic, white Seventh-Day Adventists, aged 27–95, who lived in California between 1967 and 1992. All participants completed a lifestyle questionnaire before enrolment in 1976. Follow-up surveys were done in 1977, 1987, and 1992. Only 2·5% of the participants were lost to follow-up. Hourly estimates of ambient ozone, sulphur dioxide, and nitrogen dioxide were made by use of data from 348 fixed-site Californian Air Resources Board monitoring stations. PM10 records began in 1987 so estimates for before 1987 were drawn from the records of total suspended particles (Am J Respir Crit Care Med 1999; 1 5 9 : 3 7 3 – 8 2 ) . In men, PM10 exposure was strongly associated with lung cancer (adjusted relative risk [RR] 2·38, p<0·01). PM10 exposure was also associated with all natural causes of death (RR 1·12, p<0·05) in men and with an increased mortality from non-malignant respiratory disease in men and women. In addition, ozone exposure was implicated in increased risk of lung-cancer mortality in men, and SO2 exposure was independently associated with increased risk of lung-cancer mortality in men and women. Lead author David Abbey (Loma Linda University, CA, USA) believes that the differences between men and women may partly be a result of the amount of time each sex spent out-ofdoors, noting that men who spent longer outside were at greater risk than men who spent most of their time i n d o o r s . Environmental scientist Steven Smith of Kings’ College London, UK, thinks that the paper is a “very significant contribution to the debate on the effects of air pollution on respiratory health”. He is surprised by the strength of the correlation between PM10s and lung cancer, because previous evidence linking PM10 and ozone exposure with lung-cancer risk has been equivocal. He also notes that “the causative agent has yet to be isolated” and says that it must be remembered that “recent studies on the short-term effects of atmospheric particles on respiratory and cardiovascular diseases have shown that PM2·5s and even smaller particles are more important than PM10s”.

Excessive breast self-examination may promote anxiety

1073 New antidepressants no better than old O antidepressants, such as first and second generation tricyclics, and newer compounds, such as selective serotonin reuptake inhibitors (SSRIs), are about equally effective to treat depression, according to a report released by the US Agency for Health Care Policy and Research. The report reviewed more than 300 randomised trials that evaluated newer medications for depression, and also considered evidence for three herbal remedies: St John’s wort, valeriana, and kava kava. Study participants discontinued newer and older antidepressants at about the same rate but fewer quit SSRIs because of adverse effects. St John’s wort appeared to be more effective than placebo for the shortterm treatment of mild to moderately severe depressive disorders, the report found. “These findings are tempered by the relatively small number of trials and evidence of publication bias favouring positive trials.” No trial data for kava kava and valeriana could be found. The report summary is at http://www.ahcpr.gov/ clinic/deprsumm.htm and the full report will be available in mid-1999.

Deep-vein thrombosis link to travel strengthened

160 patients admitted to Hopital Pasteur, Nice, France, with deepvein thromboses or pulmonary embolism and 160 matched controls admitted for an event other than venous thromboembolic disease completed a 300-item questionnaire on admission and on discharge. 12 of the questions were about recent travel. More patients admitted for venous thromboembolic disease had recently made a long journey than had patients in the control group (24·5% v s 7·5%; p<0·0001). For those patients in the venous-thromboembolic-disease group who had travelled, average journey duration was 5·7 hours. Clots were found in the calf, and in the popliteal, femoral, and iliac veins. One patient had a pulmonary embolism but no documented deep venous clot. No specific clot location was associated with travel (Chest 1999; 115: 440–44). Lead author Emile Ferrari explains that most travel-related venous thromboembolic diseases are not recognised because the patient presents many days or weeks after the journey during which the clot originally developed. Vascular physician Alexander Cohen (King’s College, London, UK) says that this study reinforces the need to advise all travellers to exercise their legs and feet regularly and to keep well hydrated. He also suggests that people at minor risk of venous thromboembolic disease take an aspirin before long journeys and that those with a history of such diseases should be given subcutaneous low-molecular-weight heparin.