|
Environmental Sources
Sulphur dioxide, or SO2, belongs to the family of sulphur
oxide gases (SOx). Sulphur is prevalent in all raw
materials, including crude oil, coal, and ore, that contain common metals
like aluminium, copper, zinc, lead, and iron. SOx gases are formed when
fuel containing sulphur, such as coal and oil, is burned, and when gasoline
is extracted from oil, or metals are extracted from ore. SO2
interacts with other gases and particles in the air to form sulphates
and other products that can be harmful to people and their environment.
Sources of SO2 are industrial facilities that derive their
products from raw materials like metallic ore, coal, and crude oil, or
that burn coal or oil to produce process heat (e.g. oil refineries).
Human Health Effects
SO2 contributes to respiratory illness, particularly in children
and the elderly, and aggravates existing heart and lung diseases. High
levels of SO2 emitted over a short period, such as a day, can
be particularly problematic for people with asthma. Peak levels of SO2
particularly affect people with asthma.
Asthma is an inflammatory disease with episodic symptoms of airflow
obstruction with at least partial reversibility. Typical symptoms of asthma
are: eye and upper respiratory irritation, chest pain, shortness of breath,
cough, wheezing, nausea, malaise, headache; and signs are: conjunctival
and upper respiratory inflammation, lung inflammation and infection, wheezing.
Symptoms of asthma and other chronic lung diseases are often precipitated
by increased levels of air pollutants including NOx, O3, SO2
and particulates and the increased incidence of asthma in winter may be
related to effects of temperature inversions on industrial and vehicle
–generated pollution. For more information on asthma go to www.epa.gov/children/asthma.htm
When
SO2 is oxidized to sulphuric acid, this transformation process
is facilitated by moisture and sunlight to form aerosol sulphates. Aerosol
sulphates are in the form of secondary particulates in the respirable
range (less than 2 micrometers) and penetrate deep into the lungs where
irritation occurs. These small respirable particles are not retained by
the mucous membranes of the nose and throat and penetrate deep into the
lungs where they are deposited into the alveoli. This causes breathing
difficulties and aggravates asthma
Exposure limits
- United States EPA’s National Ambient Air Quality Standards (US NAAQS)
has set an air quality standard of 30 ppb for long-term 1-year average
concentrations of sulphur dioxide. Short-term, 24-hour air concentrations
should not exceed 140 ppb more than once a year.
- The US Occupational Safety and Health Administration (OSHA) has set
a limit of 2 ppm over an 8-hour workday, 40-hour workweek.
- The South African Department of Environmental Affairs and Tourism’s
(DEAT) guideline values for Sulphur dioxide are as follows: 600 ppb (hourly
average), 300 ppb (daily average), 100 ppb (monthly average) and 50 ppb
(annual average).
- The World Health Organisation (WHO) has a guideline limit of 191 ppb
for a 10-minute (instantaneous) peak, 48 ppb for a daily average and a
19 ppb annual average.
Sources & Links:
www.ceroi.net/reports/durban/issues/air/guidelin.htm
www.epa.gov/oar/aqtrnd99/chapter2.pdf
www.who.int/environmental_information/Air/Guidelines/Chapter3.htm#3.1
www.epa.gov/children/
www.epa.gov/acidrain/ardhome.html
www.epa.gov/oar/aqtrnd97/brochure/no2.html
www.epa.gov/air/urbanair/so2/what1.html
www.epa.gov/air/urbanair/so2/hlth1.html
www.psr.org/breathe.htm
www.modcon.co.il/exposure.htm
Back to chemical profiles
| 