It was then further tested and found to contain four parts per billion of bute.
It peaks at just under about 0.6 between 50 and 100 parts per billion of air pollution.
In 2011, concentrations reached a new high of 1813 parts per billion (ppb), 259% higher than pre-industrial levels.
In 1996 the city had to shut it down after recording MTBE contamination readings of 610 parts per billion.
The measured magnetic moment of the electron agrees with that predicted by the Standard Model to within four parts per billion.
Concentrations of nitrous oxide, estimated to be nearly 300 times more potent than carbon dioxide, rose slightly to a record 324 parts per billion.
Europe allows juice imports that contain as much as 200 parts per billion of carbendazim, and Japan and Canada allow even more of the chemical.
Levels of methane, a more potent greenhouse gas, hit a new record at 1, 813 parts per billion - more than two-and-a-half times the pre-industrial level.
Before he left office, former President Clinton enacted regulations that called for lowering the arsenic standard from 50 parts per billion to 10 parts per billion.
The Clinton administration changed the standard that had been set in 1942 from 50 parts per billion of arsenic in drinking water to 10 parts per billion.
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California won't allow public water utilities to use water containing MTBE with concentrations higher than 5 parts per billion, a standard cheered on by greenies and ethanol makers.
Only in the quartile with exposures above 31.8 parts per billion do the odds values exceed 1, yet the figure suggests that at higher levels, probability starts to drop again.
Lawyers for the oil industry say the vast majority of the plaintiffs have given them data that show very low levels of MTBE contamination in the small parts per billion category.
Nitrous oxide, emitted into the atmosphere from natural and man-made sources, including biomass burning and fertiliser use, was 323.2 parts per billion in 2010 - 20%higher than in the pre-industrial era.
In 2010, the European Food Safety Authority published a report outlining analysis of 612 rice samples from the EU, finding average levels of just a few tens of parts per billion.
On the horizontal axis of each graph, we have total traffic-related air pollution exposure, increasing in parts per billion (a part here would be a drop in a billion drops) from left to right.
My favorite example of this environmental excess is the ground water cleanup efforts around Sacramento, California, where one aerospace company has managed to reduce the incidence of rocket-fuel ingredient perchlorate to four parts per billion.
To prove that MTBE concentrations below the EPA's threshold still made water taste terrible, Summy unearthed documents like a 1983 Shell letter detailing that water was no longer drinkable where MTBE'S concentration was 7 to 15 parts per billion.
An extensive study in 2012 by US magazine Consumer Reports, including rice and rice-based products such as rice cakes and drinks available in the US, measured lead levels even lower, with a majority of samples measuring less than five parts per billion.
Raun and Ensor conclude that federal air quality standards are adequate where ozone levels are concerned (at 75 parts per billion), but that lives would be saved if particulate matter standards were tightened below the current level of 35 micrograms per cubic meter of air.
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The Dutch authorities' independent study of 26 samples of rice imported from Asian nations found average levels of seven parts per billion - a thousandth of those found in the original study - and with no samples above the EU limit of 200 parts per billion.
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