Sentences with phrase «when ozone levels»

At its worst it can help create seven more days a year when ozone levels exceed air pollution limits.

Since the 1980s the most severe ozone layer depletion has been regularly observed over Antarctica during spring, when ozone levels drop by over 95 % and UV radiation reaching Earth's surface increases substantially.

Average number of days per year (2010 - 2014 average) when ozone levels exceed the US health - based air quality standard of 70 parts per billion (ppb) averaged over eight hours, at non-urban and urban sites.

Not exact matches

Ground - level ozone is a secondary pollutant, meaning that it is not emitted directly, but forms when sunlight triggers reactions between natural and human - caused chemical emissions, known as ozone precursor gases.

Some researchers have pinned the blame on indoor air pollution and a study last year showed that when outdoor ozone levels rose, the number of people inside suffering from so - called «sick building syndrome» also increased.

Solomon and her colleagues believed they would get a clearer picture of chlorine's effects by looking earlier in the year, at ozone levels in September, when cold winter temperatures still prevail and the ozone hole is opening up.

Atmospheric scientist Maria Zatko was close to completing her thesis on ground - level ozone in 2014 when she learned of a perfect opportunity to fill a gap in her research on this air pollutant.

When certain trees dominate a street, they can raise the ozone level considerably.

For example, he says, the cosmic ray effect could explain why CFC and ozone levels decline during the Antarctic winter, when ultraviolet radiation is scarce.

A new study of 60 million Americans — about 97 % of people age 65 and older in the United States — shows that long - term exposure to airborne fine particulate matter (PM2.5) and ozone increases the risk of premature death, even when that exposure is at levels below the National Ambient Air Quality Standards (NAAQS) currently established by the U.S. Environmental Protection Agency.

In the summer, when these weather patterns subside, ozone levels in national parks are still above what would be expected given U.S. reductions in ozone - precursors.

A Northwestern University study by an economist and a chemist reports that when fuel prices drove residents of São Paulo, Brazil, to mostly switch from ethanol to gasoline in their flexible - fuel vehicles, local ozone levels dropped 20 percent.

When residents of São Paulo chose gasoline over ethanol to fuel their vehicles, levels of ozone actually decreased, according to a Northwestern study.

When the researchers discounted the data about lightning flashes over Africa, the predicted ozone levels dropped significantly.

The ozone season is selected because it is the part of the year with highest temperatures and strongest solar radiation and thus the time when photochemical reactions of ozone precursor gases are most likely to produce high ozone levels (Rice, 2014).

When ozone exposure decreased by 10 parts per billion — and was at a level well below the federal air quality standard — the workers were 5.5 percent more productive.

Ozone helps shield the planet when it's high in the atmosphere, but at ground level it is a pollutant that can make asthma symptoms worse.

We've expressed puzzlement that the agency wants to impose more stringent standards when the existing ones are working — lowering ozone levels 18 percent between 2000 and 2013 according to EPA's own data.

There is growing evidence from EuroHEAT that the effects of heat - wave days on mortality are greater, particularly among the elderly, when levels of ozone or particulate matter are high.

The Freon bubble burst when, in 1989, the ozone layer suddenly jumped to the pre-Montreal Protocol level and has since continued to rise.

If this happens during northern winter, surface pressure falls in the Arctic (rising AO) the night jet stalls, NOx injection falls away, stratospheric ozone levels increase, the coupled circulation is invigorated and pressure falls at 50 - 60 ° north and this is associated with cloud loss (when global cloud cover is at its maximum value) and a strong rise in global sea surface temperature.

As if sweltering heat weren't bad enough, Europeans also suffered through a higher - than - normal number of days with dangerous smog levels that year.6 Smog — with ground - level ozone as the main component — forms when sunlight reacts with chemicals such as volatile organic compounds, carbon monoxide, nitrogen oxides, and water vapor.

During extreme heat events, nighttime temperatures in the region's big cities are generally several degrees higher28 than surrounding regions, leading to increased heat - related death among those less able to recover from the heat of the day.36 Since the hottest days in the Northeast are often associated with high concentrations of ground - level ozone and other pollutants, 37 the combination of heat stress and poor air quality can pose a major health risk to vulnerable groups: young children, the elderly, and those with pre-existing health conditions including asthma.29 Vulnerability is further increased as key infrastructure, including electricity for potentially life - saving air conditioning, is more likely to fail precisely when it is most needed — when demand exceeds available supply.

Ozone helps shield the planet when it's high in the atmosphere, but at ground level it is a pollutant that can make asthma symptoms worse.

Inexorably rising levels of background tropospheric ozone result from the VOC emissions created when burning fuel, reacting to UV radiation.

Don't worry about that, methanol is going to be far worse and when large quantities of hydrogen gas are released into the upper atmosphere there is going to be all sorts of fun with ozone, hydroxyl radical and NOx levels.

Repeating NASA's question, «Why are we seeing the worst - ever ozone hole when 13 years of regulation are finally bringing CFC levels under control?»

«In 1999, when Houston's ozone levels were the highest in the nation, the state of Texas conducted several studies that found large industrial leaks,» the report notes.

He presented data of ozone levels over Toronto for a period when I knew there were no such measures; he particularly stressed one very low reading.

«Refuel your car after 6 p.m. instead of during the day, when heat allows emissions in the air to form ground - level ozone.»

This myth arose from a misinterpretation of an out - of - context quotation from a review article (Dobson, 1968), where he mentioned that when springtime ozone levels over Halley Bay were first measured, he was surprised to find that they were about 150 Dobson Units below springtime levels in the Arctic.