On one day, pollution levels were 30 times higher than levels deemed safe by the World Health Organisation (WHO).
There was also a significant rise in deaths involving antidepressants, up from 393 in 2012 to 468 in 2012 but lower than levels seen in the 1990s.
On 12 January, Beijing's AQI hit a record 755, 30 times higher than levels deemed safe by the World Health Organisation.
The concentration of T.H.C. in the blood of a deceased person can be much higher than levels in a living person, Dr. Lemos said.
The overall 3.9percentt increase in violent crime in 2015 was lower than levels from five and 10 years ago, the F.B.I. said.
The European Union has promised to cut emissions to a level 20percentt lower than levels in 1990, and by 30percentt if other wealthy nations follow suit.
But it remains much stronger than levels of around 108 yen a year ago and will continue to be a serious drag on the Japanese economy.
Arsenic in some areas is 10 to 50 times higher than levels considered safe, Vietnamese officials said.
"Even at the sites that were essentially our background baseline sites, we measured 30 nanograms per liter – that's higher than levels known to cause sexual differentiation issues in snails and some amphibians," Kassotis says.
Temple, author of a book on the opioid crisis called American Pain, cautioned that although the drops were significant, the limits were still much higher than levels in the 1990s and 2000s.
Those levels fell much more rapidly, for instance, than levels of the mercury people absorb by eating fish — suggesting that the injected thimerosal is less likely to build up in the blood, the researchers concluded.
