Vehicular Exhaust and Air Pollution

Introduction

Individual tailpipe emissions

Transport and fate in the environment

Measuring exposures

Prevention and control of exposure

Exposure Pathway

Risk assessment

Adverse effects

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Adverse Effects

Health Effects of Ground-Level Ozone

Looking out over Los Angeles, one notices a brown haze enveloping the city. This brown haze is made up largely of ozone a key component of smog. Ozone is formed when hydrocarbons and nitrogen dioxides, which are two vehicular exhaust pollutants, are exposed to sunlight. Ozone does not often act alone in the environment, it is normally accompanied the other main pollutants. Therefore ozone shares several adverse health effects with other pollutants such as particulate matter and nitrogen oxides. VOC + NOx + Heat + Sunlight = Ozone

How are people adversely affected?

Ultimately everyone who breathes ambient air contaminated with ozone has the potential of being adversely effected. The following effects are short term because they normally cease after the individual is removed from the high ozone environment.

  • Irritation of the respiratory system
    Symptoms: coughing, irritation in the throat and/or uncomfortable sensation in the chest, may become painful
  • Reduction of lung function
    Symptoms: more difficult to breathe as deeply and vigorously, breathing becomes uncomfortable, shorter breaths
  • Aggravation of asthma
    Symptoms: asthma attacks during high levels of ozone because ozone makes people asthmatics more sensitive to allergens
  • Inflammation and damage of the lungs’ lining
    Symptoms: possible permanent lung damage from “sun burn-like” effects of high ozone levels on the cells lining the lungs, while they are replaced in a couple of days the repeated process could cause permanent lung damage
  • Other suspected effects include aggravating chronic lung disease and reducing immune system efficiency (in animals).

Who is most susceptible?

  • Children during the summer months when ozone levels are at their peak spend a lot of time outside, running and playing. The combination of increased air intake and growing lungs has shown more occurrences of asthma in children in high ozone levels, “hot spots”. Also those children already with asthma have increased hospital visits and asthma attacks on especially high ozone days.
  • Healthy adults who are active outdoors have increased air intake causing them to have a higher exposure to ozone. People who work or exercise are included in this group.
  • People with respiratory diseases typically experience the health effects of ozone at lower concentrations than their healthy counterparts. Currently there is no proof that ozone causes these diseases. Once they are present, however, they make the lungs more sensitive to ozone.
  • There are still others that are more susceptible to ozone for no scientifically proven reason. They just are more sensitive.

Effects of Nitrogen Oxides, NOx

The most common nitrogen oxide is NO2, which is visible in combination with particles as the reddish-brown layer hanging over a city. Motor vehicles are responsible for 49% of NOx emissions. Even rural areas with low vehicle density are susceptible to high levels of NOx because it can travel long distances with wind currents. NOx is a problem on several levels.

  • It is a necessary component of ground-level ozone
  • Reacts to form nitrate particles, acid aerosols, which cause respiratory illness
  • Contributor to acid rain
  • Deteriorates water quality and skews nutrient levels
  • Creates particles that cause visibility impairment
  • Can react to form toxic chemicals

Effects of Carbon Monoxide, CO

Carbon Monoxide is formed when carbon fuels are not completely burned. Motor vehicles create 56% of CO emissions in the atmosphere. CO is dangerous because it binds preferentially to hemoglobin, reducing the amount oxygen in the blood. The two most serious effects of CO are to the cardiovascular system and central nervous system. Both are due to reduced oxygen in the blood and brain.

Effects of Particulate Matter, PM10

Particulate matter refers to the particles found in the air, including dust, dirt, soot, smoke and liquid droplets. These particles are emitted by motor vehicles directly and by motor vehicles driving on unpaved roads. PM10 is one cause of reduced visibility and aesthetic damage to buildings in the form of soot staining buildings.

Health effects include:

  • Aggravated asthma
  • Increased coughing and difficult/painful breathing
  • Chronic bronchitis
  • Decreased lung function
  • Increased hospital visits and lost work days
  • Premature death

Environmental effects from particles traveling long distances and then settling on the ground or water include:

  • Making lakes and streams acidic
  • Changing the natural balance of waterways
  • Depleting the natural soil nutrients
  • Damaging sensitive forests and crops
  • Affecting ecosystems

References:

Korensein, S. "An Exposure Assessment of Pm10 from a Major Highway Interchange: Are Children in Nearby Schools at Risk?" Journal of Environmental Health 65.2 (2002): 9-17.
http://www.epa.gov/air/urbanair/nox/index.html
http://www.epa.gov/air/urbanair/6poll.html
http://www.epa.gov/air/urbanair/pm/index.html