Page 32 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

1.3 Effects of Air Pollution and GHGs 5

1.3 Effects of Air Pollution and GHGs

Clean air is essential to humans and other living beings on Earth. One can survive
without water for 2 days or food for 2 weeks, but very few can survive a few
minutes without air. On a daily base, an average adult consumes 2 kg of water [25],
1 kg of food and 20 kg of air. However, polluted air impacts public health when the
pollutant concentrations are high enough. Polluted air also affects the environment
by lowering its visibility and damaging the other species and materials on the
planet. Excessive GHGs in the atmosphere affect Earth’s energy balance and,
consequently, the climate and weather. The effects of air pollution and GHGs are
introduced in the following subsections.

1.3.1 Health Effects of Air Pollution

Poor air quality is responsible for one out of eight global deaths [31]. Air pollution
has become the single largest environment and health challenge to society. Air
pollution has a direct negative effect on human health. Acute air pollution episodes
can result in cardiac and respiratory diseases, bronchitis, pneumonia, and some-
times death. Historically, these conditions occurred in many places, including
Muese River Valley, Belgium (1930), Donora, Pennsylvania, USA (1948), London,
England (1952, 1962), New York City (1953) and Bhopal, Indian (1984). It is still
happening: for example, the most recent outbreak of smog in many Chinese cities,
which were responsible for the deaths of 1.2 million/year in China.
Air pollutants enter the human body (or that of any creature) mainly through
the respiratory system, although they can also be ingested or absorbed through the
pores of skin. Part of the inhaled air pollutants can be exhaled, but most reach the
lungs, with some penetrating through the lungs and entering the circulation system.
These contaminants can be then transported all over the body, with some chemical
reactions forming new chemicals.
Toxic chemicals can interfere with normal body functions, resulting in many
health problems. Some of these effects are acute, including eye irritation, head-
aches, and nausea, while others may be chronic and irreversible, such as organ
damage, birth defects, heart disease, cancer, and even death.
Aerosol particles are deposited into the respiratory system at different locations
according to particle sizes. Particles larger than 15 μm (in diameter, which is this
book’s default unless stated otherwise) are captured by small nasal hairs or mucus
membranes. Particles smaller than 10 μm are trapped in the cilia, which are the
body’s last line of defense in the bronchioles before reaching the alveoli. The lower
respiratory system is composed of the bronchi, bronchioles, and alveoli, where most
pollutant exchange occurs. Alveoli contain millions of tiny air sacs. Most particles
between 1 μm and 100 nm (=0.1 μm) settle in the alveoli. Alveolar tissue holds the
particles in place for weeks to years. The toxins and chemicals adsorbed by the
particulates are then dissolved and transported to the circulation system of the body.