The daily fluorine and arsenic intake for residents with different dietaries and fluorosis risk in coal-burning fluorosis area, Yunnan, Southwest China.

The daily fluorine (F)/arsenic (As) intake (DFI/DAsI) for residents at different ages with different dietaries and dietary changes was investigated to analyze the fluorosis risk in coal-burning fluorosis area in Yunnan, Southwest China. The DFI for residents with a dietary of roasted corn and roasted chili was 5.06, 9.60, and 14.38 mg for age groups 3-7, 8-15, and over 15 years, respectively. Over 90 % of DFI was from roasted foodstuffs. The DFI for residents of the same age group living on rice and roasted chili was 1.94, 3.50, and 4.95 mg, respectively, which were less than that for the former dietary type, and 65 % of DFI was from roasted chili. The main sources for their DFI are roasted foodstuffs. Both were higher than the dietaries with non-roasted foodstuffs and the recommended daily allowances (RDAs) for USA and China at different levels. The DAsI for all residents ranged from 25 to 135 µg, and at this level of DAsI, it would not influence human health. However, As pollution of roasted foodstuffs might have an important influence for the fluorosis. Residents are changing their staple food from roasted corn to rice, and especially, younger people are more focused on quality life. However, even if residents change their staple food, the habit of eating chili will not change, which also may cause them getting fluorosis. Developing economy, changing dietary types, and changing the habit of drying and keeping chili will help to reduce the fluorosis risk in coal-burning fluorosis area of Southwest China.

Calibrating the end-Permian mass extinction.

The end-Permian mass extinction was the most severe biodiversity crisis in Earth history. To better constrain the timing, and ultimately the causes of this event, we collected a suite of geochronologic, isotopic, and biostratigraphic data on several well-preserved sedimentary sections in South China. High-precision U-Pb dating reveals that the extinction peak occurred just before 252.28 ± 0.08 million years ago, after a decline of 2 per mil (‰) in δ(13)C over 90,000 years, and coincided with a δ(13)C excursion of -5‰ that is estimated to have lasted ≤20,000 years. The extinction interval was less than 200,000 years and synchronous in marine and terrestrial realms; associated charcoal-rich and soot-bearing layers indicate widespread wildfires on land. A massive release of thermogenic carbon dioxide and/or methane may have caused the catastrophic extinction.