Nitrogen dioxide sources and health effects in the United States

Nitrogen Dioxide

KILLING U.S. SOFTLY?

Chemical and Physical Data

Nitrogen Dioxide or NO2 is a red-brown or yellow liquid, which becomes a colorless solid at a specific temperature (EPA 2007). It is a non-combustible component of automotive exhaust fumes. It can be derived during the intermediate stage in the oxidation of ammonia to nitric acid. It is highly poisonous and even fatal when inhaled. Tolerance in the air is at 5 ppm. Nitrogen dioxide can react strongly with reducing materials. It occurs as environmental tobacco smoke and artificially as kerosene heaters, un-vented gas stoves and heaters. Among its effects on health are irritations on the eyes, nose and throat; pulmonary edema and diffused lung injury; chronic bronchitis; decreased lung function; and increased risk of respiratory infections, especially in young children (U.S. Environmental Protection Agency).

Interaction in the Environment

Nitrogen is found in the air, in water and in the soil. There are more automobiles than agriculture, thus nitrogen is more present in the air (Fields 2004). It forms from nitrogen fertilizers, burning of biomass and combustion of fossil fuels. As smog and ground-level ozone, it is the most important part of air pollution. NO is found in high concentrations in urban areas on account of their high car populations. These produce low-lying ozone, which in turn, produces or worsens asthma, cough, reactive airways disease, respiratory tract inflammation and chronic respiratory disease. This pollutant can also make viral infections worse. At mid-altitude, it acts as a greenhouse gas, it can absorb roughly 200 times outgoing radiation as carbon dioxide. At low altitudes, it increases ozone. And it actually destroys ozone at very high altitudes. Destroying ozone in the stratosphere would allow more ultraviolet light to enter the earth's surface and afflict human beings with skin cancers. Reductions in the ozone layer could explain the 20-40% increase in skin cancers since the 70s. Nitrogen gases in the air can also produce tiny particulates, which can enter deep into the lungs and contribute to cardiovascular diseases, respiratory diseases, asthma, weakened lung function and overall mortality (Fields).

Nitrogen is highly soluble in water and quickly seeps down the root zone of an agricultural field, forest and groundwater (Fields 2004). At that level, it would be difficult to control. In bays and coastal zones, it becomes a steady source of food to algae. When these algae die, they sink and decay. The process draws oxygen from the water. When too much is taken out, the body turns into a "dead zone," an area which cannot sustain aquatic life. Reactive nitrogen can also reach and infect drinking water from nitrogen fertilizers and runoff from livestock. High concentrations of nitrates can bring on the "blue baby disease," which weakens the blood capacity to carry oxygen. Nitrates have also been blamed for reproductive ailments and cancers of the bladder and ovaries.

And nitrogen is found in the soil. The soil, however, takes it up only up to a limit (Fields 2006). Beyond that limit, the soil will shed it off and become saturated. But shed off nitrogen leaves the soil with other nutrients. The soil acidifies and the whole system thrown out of balance (Fields).

The United States Environmental Agency reported that transportations operating on ultra-low sulfur diesel could hit the 2007 limit on heavy-duty emission standards (Peckham 2000). The new report said a trap system technology would be needed but did not say that it was already commercially ready. Even the slightest fuel sulfur would ultimately impact nitrogen trap performance, according to the EPA. The agency believed that a reliable trap desulfurization scheme should be added to the trap system. Residual sulfur masking would reduce NO trapping strength. More frequent desorption or conversion would avoid NO slipping from a "full" trap (Peckham).

Swedish-based International Geosphere-Biosphere Program and the French-based Scientific Committee on Problems Program merged to support the International Nitrogen Initiative or INI to address the problems on nitrogen cycle changes (Fields 2004). Their project would assess the status of knowledge on nitrogen flows and problems. It would come up with region-specific strategies and set these strategies in the proper places. Regional centers would be established to implement the goals. The INI, in turn, co-sponsored the Third International Nitrogen Conference in October 2004 in Nanjing, China. The participating scientists focused on problems germane to Asia and reviewed its options for increasing food and energy production while reducing nitrogen use and pollution. The INI Scientific Advisory Committee met to plan on setting up regional centers for Asia. In the end, the participants confronted the same objective and need to regulate reactive nitrogen the same way as other pollutants has been or has to be regulated. Europe has installed regulations that have shown to help reduce nitrogen pollution, according to reports. In comparison, the United States and developing nations still have to adequately understand the dynamics of the nitrogen cycle before they can come up with regulations and implement them (Fields).

Effects on the Human Body

According to a 2007 United Nations report, the combination of agricultural activities and fossil fuel combustion presently releases 125 million metric tons of nitrogen a year (Bohan 2007). In comparison, natural sources release 113 million metric tons at the same frequency. The same report said that there was virtually no such nitrogen release from human activity in 1860. This overdose has disrupted ecosystems, polluted waters and injured human health. Most importantly, it has been changing the earth's climate in cooperation with another harmful element, carbon dioxide or CO2.. There have been serious efforts at reducing CO2 but these would be futile unless nitrogen release was also reduced. A single nitrogen compound cast into the atmosphere can bring a lot of trouble. It stays there for a century and has shown to be more capable of trapping heat than CO2. Head of Climate Change and Carbon Management Program Margaret Torn said that the changes now occurring to the nitrogen cycle are greater and more profound that those to the carbon dioxide cycle. The former had been neglected. This was a very serious kind of neglect, she said. She concluded that unless the nitrogen problem was confronted and adequately contained, climate change would not be solved (Bohan).

Toxicity

EPA established that exposure to indoor NO below the 53 ppb outdoor standard could lead to respiratory symptoms among children with asthma, especially in a multi-family setting (Belanger 2006). This effect continues to be a public health issue because of the number of people exposed to the gas. According to the U.S. Census, more than half of all U.S. households use gas. Their primary source of residential NO is a gas-fueled cooking appliance. This was the summary finding of a study conducted with 1,002 participating families in Connecticut and southwestern Massachusetts from 1997 to 1999. It associated indoor NO with increased respiratory symptoms among asthmatic children. At present, there are no U.S. standards for indoor levels of NO. But these levels found to have significant health effects among asthmatic children in this setting are similar to the outdoor annual exposure of 21 ppb recommended by the World Health Organization (Belanger). The EPA fixed.053 ppm as the average 24-hour limit for NO2 outdoors.

Regulations

In addressing the growing concern over NO gases, the Environmental Protection Agency planned to propose emission standards for "stationary" diesel engines (Osenga 2005). The New Source Performance Standards, according to EPA, would reduce these harmful emissions of nitrogen oxides, particulates, sulfur dioxide, carbon monoxide and hydrocarbons from new, altered and re-manufactured stationary diesel engines. Stationary engines are those commonly used in power generation, compressor or pump sets. According to EPA, they are reciprocating, rotary and other internal combustion engines. These standards would subject such engines to the same levels set by EPA's non-road diesel engine standards (Osenga).

These standards would be in keeping with the demands of the lobbying group, Environmental Defense, that EPA complete a final stand by June 28, 2006 (Osenga 2005). They considered technologies, costs of control and fuel requirements, which would reduce the sulfur content in the engines. EPA said that these rules would take effect in three stages. The first would be a transition period for engines built after the year of the proposal but before the 2007 modal year. Each owner would be obliged to purchase an engine and operate and maintain it according to manufacturer's instructions. He would, in most cases, buy a certified off-highway engine for stationary use. If not, it would be a non-certified engine, which should comply with emission limits set before 2007, according to EPA. Engines manufactured from 2007 would need to certify that their engines meet the required emissions levels for the same size engine and model year for non-road engines in the Tiers 1 to 4 categories (Osenga).

Of the total amount of nitrogen created to sustain food production, only 2-10% turns into food and actually consumed (Fields 2004). The rest gets lost in the environment. Since the un-consumed reactive nitrogen does not return to molecular level, it must have found its way into the environment, in the air, in the groundwater or in the soil. The solutions will not come fast and easy. At best, they will be long-term or not likely. One view is for meat-eaters to become vegetarians so that farmers would plant less nitrogen-dependent grains. Most of these become animal feed and mere sweeteners. Unfortunately, meat eaters have been increasing in the United States and in Asia instead of decreasing. Genetically engineering a symbiotic type of bacteria to grow grains with nitrogen-fixing capability came up as an idea (Fields).

Suggestions for Action

Better than planting less nitrogen-dependent grains and genetically engineering a special type of bacteria is to improve methods of crop rotation and land fertilization (Fields 2004). Farmers should add only the exact and right amount of fertilizer only when it is needed instead of over-fertilizing the land. Ultimately, the solution is to regulate reactive nitrogen and other pollutants. University of Virginia Environmental Sciences Professor James Galloway mentioned said that a lagoon system was one regulation. It was to decrease nitrogen-containing waste released in water by storing the water in the lagoons and aerated to release ammonia into the atmosphere. The sludge, which remained, was spread out into the fields as crop cover. However, this system would only transfer the NO into the atmosphere. An integrated management policy was needed. The problem that remained was the lack of knowledge on the rate of NO accumulation. What was certain was that reactive nitrogen compounds the already numerous environmental problems existing. The more NO released in the environment, the greater the accumulation rate and the greater the negative impacts or effects. Scientists have acknowledged that the ill consequences are varied and already widespread. They know something really effective must be done about it without turning socioeconomic systems upside down (Fields).

The average NO in homes even without combustion appliances has been measured as half of that outdoors (U.S. Environmental Protection Agency 2007). Levels in homes with gas stoves, kerosene heaters or un-vented gas space heaters exceed those in the outdoors. Responsible citizens could help or contribute to the overall objective of reducing reactive nitrogen dioxide exposure by observing these tips:

Vent NO2 sources in the outdoor. Make sure combustion appliances are properly installed, used and maintained most effectively. The same steps can be followed to reduce exposure to carbon dioxide, the other killer.

Adjust gas appliances properly.

Whenever possible, purchase a vented space heater when replacing an un-vented one.

Use the proper or appropriate fuel in kerosene space heaters.

Prefer the use of an exhaust fan, vented to outdoor levels, to gas stoves.

Open flues when using fireplaces.

Use only wood stoves with sizes meeting EPA emission standards. The doors of the wood stoves must fit tightly.

Only a trained professional should inspect, clean and tune up the central heating system every year. This system includes furnaces, flues and chimneys. All leaks should be promptly repaired. The car should not be left idle in the garage.