Trends in Air Quality

Over the years, air quality in New Jersey has been improving. This chart shows that unhealthy ratings were recorded on fewer than one day in thirty over the 1995 - 1997 period, compared to ten years before that, when unhealthy ratings were recorded on about one day in eight. New, more-stringent federal health standards for both ozone and particulates went into effect by 1998. These standards are more difficult for New Jersey to meet: under the new ozone standard, there were 47 unhealthy days in 1998; only 4 days would have been rated unhealthy that year under the old ozone standard. However, these standards are now in question.

The chart below gives a longer perspective on air quality trends in New Jersey. It shows the changes since 1967 in the levels of all the pollutants for which there are federal health standards -- carbon monoxide, lead, nitrogen dioxide, ozone, particulates and sulfur dioxide. You can see that lead and sulfur dioxide regularly reached unhealthy levels 15 to 20 years ago. These pollutants now meet the national health standards throughout the state and are considered to be well under control. The particulate line in this chart shows levels below the health standard throughout the 1990's, while the chart above showed some unhealthy days due to particulates. The difference is because the unhealthy days were rated using a short-term method and standard to enable us to alert the public quickly, while the particulate levels in this long-term chart are compared to the annual health standard. Here again, however, we don't expect to be able to meet the new, more stringent particulate standard that's now in effect, even if actual pollutant concentrations don't worsen.

Air pollution levels also change during the day and from one season to another. These changes are due to variations in the weather and in the types and amounts of pollution that are released into the air, both in New Jersey and in states that are upwind of us.

Here's an example of how carbon monoxide levels changed over several days in January 1995 at North Bergen, Hudson County. A strong temperature inversion formed, trapping the pollution close to the ground and causing it to reach unhealthy levels. There haven't been any unhealthy days due to carbon monoxide in New Jersey since this episode.

Ground-level ozone is formed in the air when other pollutants chemically react. High temperature and strong sunlight are needed to produce high concentrations of ozone, so you can see why ozone peaks in the summer months and is lower at other times of the year. This chart shows the highest levels of ozone at Rutgers University in East Brunswick, Middlesex County during each month in 1997.

Among the pollutants for which no health standards have been set, some have shown changes that reflect efforts to control pollution, while others have shown little or no change over the last ten years. Volatile organic compounds (VOCs) are one group of pollutants that react chemically to form ground-level ozone. Controls on the make-up of gasoline sold in New Jersey have reduced VOC emissions and, in turn, ground-level ozone concentrations.

Many of these VOCs are "air toxics," capable of causing a variety of adverse health effects ranging from lung irritation to cancer. Benzene is an air toxic that's also a VOC. It's emitted when gasoline evaporates or is burned, and from other sources. This chart shows how benzene levels have declined in Camden from 1990 to 1997. The other air toxics we measure also show a substantial decline over the same period.