The global atmospheric environment for the next generation.

Air quality, ecosystem exposure to nitrogen deposition, and climate change are intimately coupled problems: we assess changes in the global atmospheric environment between 2000 and 2030 using 26 state-of-the-art global atmospheric chemistry models and three different emissions scenarios. The first (CLE) scenario reflects implementation of current air quality legislation around the world, while the second (MFR) represents a more optimistic case in which all currently feasible technologies are applied to achieve maximum emission reductions. We contrast these scenarios with the more pessimistic IPCC SRES A2 scenario. Ensemble simulations for the year 2000 are consistent among models and show a reasonable agreement with surface ozone, wet deposition, and NO2 satellite observations. Large parts of the world are currently exposed to high ozone concentrations and high deposition of nitrogen to ecosystems. By 2030, global surface ozone is calculated to increase globally by 1.5 +/- 1.2 ppb (CLE) and 4.3 +/- 2.2 ppb (A2), using the ensemble mean model results and associated +/-1 sigma standard deviations. Only the progressive MFR scenario will reduce ozone, by -2.3 +/- 1.1 ppb. Climate change is expected to modify surface ozone by -0.8 +/- 0.6 ppb, with larger decreases over sea than over land. Radiative forcing by ozone increases by 63 +/- 15 and 155 +/- 37 mW m(-2) for CLE and A2, respectively, and decreases by -45 +/- 15 mW m(-2) for MFR. We compute that at present 10.1% of the global natural terrestrial ecosystems are exposed to nitrogen deposition above a critical load of 1 g N m(-2) yr(-1). These percentages increase by 2030 to 15.8% (CLE), 10.5% (MFR), and 25% (A2). This study shows the importance of enforcing current worldwide air quality legislation and the major benefits of going further. Nonattainment of these air quality policy objectives, such as expressed by the SRES-A2 scenario, would further degrade the global atmospheric environment.

Pulmonary pathology of Erdheim-Chester disease.

Erdheim-Chester disease (ECD) is a rare non-Langerhans' cell histiocytosis that may present with pulmonary symptoms. The condition seems to be nonfamilial and typically affects middle-aged adults. Radiographic and pathologic changes in the long bones are diagnostic, but patients often present with extraskeletal manifestations. Advanced pulmonary lesions are associated with extensive fibrosis that may lead to cardiorespiratory failure. The clinical, radiologic, and pathologic features of six patients with ECD with lung involvement are presented. The patients were three men and three women (mean age, 57). Five presented with progressive dyspnea, and one presented with diabetes insipidus. Open-lung biopsies showed histiocytic infiltrates in a lymphangitic pattern with associated fibrosis and lymphoplasmacytic inflammatory infiltrates. The histiocytes did not stain with periodic acid-Schiff. Immunoperoxidase studies performed on specimens from five of six patients showed that the histiocytes were positive for CD68 and Factor XIIIa and negative for CD1a. Specimens from two patients exhibited immunoreactivity for S-100 protein. Electron microscopy studies performed on specimens from two patients showed phagocytic lysosomes but no Birbeck granules. Clinical follow-up of up to 16 years was available. At the end of that time, five patients were dead of complications related to their disease; one patient remains alive 4 years after diagnosis but with severe respiratory compromise. ECD is a rare non-Langerhans' cell histiocytosis that may present as interstitial lung disease and resemble other pulmonary conditions, particularly usual interstitial pneumonitis and pulmonary Langerhans' cell histiocytosis. Recognition of this entity will allow better assessment of its true incidence, therapeutic options, and prognosis.