AirPoll_Ch3

Air Pollution and Health • specific sections of the public most affected by air pollution • diseases of the cardiorespiratory system asthmatics and smokers far more likely to be affected

Air Pollution and Health

Air Pollution and Health • Pollutants act on surfaces of respiratory system = chronic respiratory and cardiovascular disease • alter O2 exchange in lungs, and transport in blood • Irritant pollutants = long term damage to eyes, nose, throat and wet surfaces of body • H2SO4 particles irritate mucous membranes and cause bronchial constriction

Air Pollution and Health • gaseous effects more acute than chronic (as opposed to the particulate pollutants) • SO2, O3 and NO2 are pulmonary irritants, may cause congestion, oedema and haemorrhage • NO, H2S and CO are asphyxiant gases • organic gas pollutants e.g. acrolein (1-propenal) as well as those gaseous pollutants mentioned above produce eye irritation

Synergism • Interaction between pollutants may be additive, synergistic, or antagonistic • Synergistic effects are those where the sum of the effects of two or more pollutants is less than the combined effect i.e. 1 + 1 = 3 • The great majority of pollutant effects are additive.

How are we affected? three main routes by which pollutants enter the body: • absorption through the skin • ingestion, and • inhalation

Air Pollution and Health

Carbon Monoxide • preferentially and irreversibly binds to haemoglobin in blood forming carboxyhaemoglobin • reduces blood's capacity to carry O2 as CO has a higher affinity (200X greater) for haemoglobin than O2 • medical evidence suggests that continued exposure to low levels of CO may cause nervous disorders and be a factor in the cause of heart disease

Carbon Monoxide • CO in urban environments usually only a fraction of those levels that cause asphyxiation • low level effects = behavioural changes, decreased time interval discrimination, impairment of brightness discrimination, increased reaction time to visual stimuli, and lowered performance in driving simulations • may be the cause of many motor vehicle accidents in peak hour traffic of cities where peak hour CO levels may rise above 50ppm

Carbon Monoxide • For cigarette smokers, CO exposures far more significant (an average 3 – 8% carboxyhaemoglobin saturation) than those experienced under urban ambient conditions

Concentration of CO (ppm)

Physiological Effect

10

Lowered awareness and driving performance

50 - 100

Headaches and drowsiness, changes in driving performance and increased reaction time to visual stimulation

>250

Death

Sulfur Compounds Sulfur Dioxide and Particulates • Analysis of the effects of SO2 complicated by association with particulate pollutants – direct effects of each individual pollutant are difficult to separate. • often produced by a common source, (combustion of coal), hence high SO2 levels often associated with high particulate matter levels - forming sulfate aerosols • aerosols just the right size to be retained in the lungs so cause maximum physiological damage

Sulfur Compounds Sulfur Dioxide • primary effect on respiratory tract, producing irritation and difficulty breathing • affects most strongly people with respiratory problems • children known to suffer increased frequency of infection upon prolonged exposure to SO2 • long term effects of exposure not well understood

Sulfur Compounds Table 3.2 – Acute effects on humans of different atmospheric SO 2 levels

[SO2] in g/m3

Effect

500

Lowest level of human sensation Threshold of taste Threshold of odour Threshold for reversible bronchial constriction Immediate throat irritation Immediate eye irritation Immediate coughing

800 1400 4400 20000 30000 50000

Sulfur Compounds Sulfur Dioxide • London smog of 1952 averaged about 40005000g/m3 • Street levels in Wollongong in the late 1970’s recorded values of 2250g/m3 – due to smelting operations • water solubility - SO2 almost entirely removed in the mouth, throat, and nose through normal breathing • < 1% of inspired SO2 reaches lung tissue (alveoli)

Sulfur Compounds Sulfur Dioxide • principal effect of SO2 exposure is to alter the mechanical function of the upper airway • SO2 exposure at low levels (0.25 and 0.5ppm) produce acute bronchoconstriction on inhalation • likely that health effects of SO2 are due to the highly irritant effects of sulfate aerosols, such as sulfuric acid, which are produced from SO2

Nitrogen Compounds Nitrogen Oxides • NO not health threat but is converted to NO2 • NO2 exposure at low levels (0.5ppm) destroy cilia and obstruct respiration • NO2 at 5ppm minor respiratory problems – 100ppm non-fatal inflammation – higher levels fatal

Hydrocarbon Compounds Hydrocarbons • Most H/C’s relatively nontoxic at the ambient levels found in normal atmospheres • Form photochemical smog = very deleterious to health - reduce visibility, have unpleasant odours and cause skin and eye irritation at higher levels - some carcinogenic, benzo[a]pyrene • H/C air quality standards not based on health effects, but an attempt to reduce photochemical smog

Ozone and Photochemical Smog Ozone • Ozone = the most toxic pollutant regulated under ambient air quality standards • may cause significant physiological and pathological changes in animals and humans at conc’s within range measured in polluted ambient environments • The ambient air quality standard for O3 is 0.12ppm (235g/m3) averaged over 1 hour

Ozone and Photochemical Smog Ozone • O3 may cause significant lung function changes even with exposures in the 0.100.40ppm range of for 1-2 hours • Exposure to O3 levels above 0.12ppm, may lead to a variety of symptoms including throat dryness, chest tightness, coughing, pain, shortness of breath, lassitude, malaise, headache, and nausea • may inhibit immune system's ability to defend the body against infection

Particulate Matter • exhibits toxic effects due to direct irritant action of particles (such as H2SO4) and substances readily adsorbed to the large surface area of small particles • concentration of adsorbed substances may be considerably greater than in ambient atmosphere • adsorbed substances of particular concern include SOx, PAH, and heavy metals e.g. Pb, Cd, Zn and Hg

Particulate Matter Retention • health consequences depend on ability to penetrate respiratory defence mechanisms • remove inhaled particles in excess of 10m, but particles smaller than can enter = inhalable particles • Particles < 2.5m = respirable, enter pulmonary tissue

Particulate Matter Retention

Particulate Matter Retention • deposition is slightly higher in smokers and greatly increased in individuals with lung disease • retention varies greatly among the different regions of the respiratory tract • ciliated airways of the nose and upper tracheobronchial zone, clearance in healthy individuals is achieved