EFFECTS OF AIR POLLUTION ON
Meera Goswami*, Dalip K. Mansotra, Shivalika Sharma,
Gaurav Pant and P. C. Joshi
Department of Zoology and Environmental Science,
Gurukul Kangri Vishwavidyalaya, Haridwar-249404, Uttarakhand,
Email: email@example.com, firstname.lastname@example.org
Air pollution is a contamination of atmosphere by gaseous, particulate
and biological molecules or by-products wh ich can be harmful for
human health and the environment. Rising issue of air pollution is an
utmost concern of the world. Among various emission sources, motor
vehicles and industrial processes contribute to the major portion of air
pollution. Much of the work on air pollution in the few decades has
centred on a small set of six pollutants, called criteria pollutants, th at
have been recognized as contributors to sulphurous and photochemical
smog. EPA (Environmental Protection Agency), USEPA has set national
air quality standards for six criteria pollutants: groun d level ozone,
carbon monoxide, nitrogen dioxide, sulphur dioxide, particulate matter
and lead. Short and long term exposure to suspended pollutants has
var iou s toxicological impac ts on hum an s inclu ding resp iratory,
cardiovascular diseases, neuropsychiatric complications, skin diseases,
eyes irritation, and long term chronic diseases such as cancer. Several
earlier studies established the direct association between exposure to
the poor air quality which results into increased rate of morbidity and
mortality mostly due to cardiovascular and respiratory diseases. Air
pollut ion is deliberat ed as the ma jor environmental factor in the
progression of some diseases such as asthma, ventricular hypertrophy,
lung cancer, Alzheimer’s and Parkinson’s diseases, psychologic al
complications, autism, retinopathy and low fetal growth.
KE YWOR DS: A ir pollu tion , Hum an he alth, E nviron me n t,
Cardiovascular diseases, Respiratory tract diseases, Toxicology.
Researches in Toxicology and Pollution (2019) : 135-144
Editor : Prof. P.C. Joshi, Namita Joshi, B.N. Pandey and Suday Prasad
Today & Tomorrow’s Printers and Publishers, New Delhi - 110 002
Air Pollution is considered to be the world’s largest environmental
health threat accounting for 4.2 million deaths every year, as a result of
exposure of ambient air pollution (Outdoor Pollution). 3.8 million deaths
every year as a result of exposure to smoke from fuels and cooking stoves
(Indoor Pollution). The mutual impacts of household and ambient air pollution
causes around 7 million premature deaths every year, mainly as an outcome
of increased mortality from stroke, heart disease, lung cancer, chronic
pulmonary disease, and acute respiratory infections. Air Pollution seems as
a current-age curse: a by-product of growing anthropogenic activities as
urbanisation and industrialisation though many physical events (volcanoes,
fire, Lightning etc.) may release different chemicals in environment. Around
91% of world population lives in an area where air quality limit exceeds
above the WHO guidelines limit. As Air Pollution is not a new phenomenon,
it has a long and evolving history. In most recent times, two alarming episodes
were occurred- In US, the episode occurred during 4 day period in 1948 in
Donora, Pennsylvania, where around 6,000 illness and 20 deaths were linked
to Air Pollution, other most worst episode occurred for a week in London,
in 1952, causes more than 4000 deaths. Air pollution is a contamination of
atmosphere by gaseous, particulate and biological particles or derivatives
which can threaten human health as well as other life forms prevailing on
Classification and Categories: On the basis of concentration of chemicals
present in environment, air pollutants can be defined. The composition of
clean air is used as a bench mark, if the concentration of chemicals is
above the concentration of chemicals present in air, it is then characterized
as an air pollutant. The Pollutants are classified as Primary and Secondary
pollutants. The primary pollutants persist in an unchanged chemical form
as they are released from a source directly into the atmosphere whereas
secondary pollutants are an outcome of chemical reactions among two or
Many Air pollutants have some similarities so, they can be grouped
into four categories:
1. Gaseous Pollutants: Nitrogen oxides (NOX), Carbon monoxide
(CO), Sulphur dioxide (SO2), Ozone (O3), Benzene, Volatile organic
compounds (VOC’S) are some of the gaseous pollutants. They
are primarily due to the combustion of fossil fuels. They contribute
to a greater magnitude in changing the composition of the
atmosphere. Majority of Gaseous pollutants affect the respiratory
system and can also induce haematological problems and cancer.
2. Persistent organic pollutants: Persis tent organic pollutants
(POPs) are the organic compounds which are resilient to ecological
degradation over biological, hydrolytic, chemical, and photolytic
processes. POPs persist in environment for an extensive period of
time, and their impressions on human and environmental health are
magnified as the y move up thr ough the food chain (bio-
magn ification). Some POPs are Dioxins, Fur a ns,
Dichlorodiphenyltrichloroethane (DDT), Polychlorinated biphenyl
(PCB), Hexachlorobenzene (HCB), Chlordane, Aldrin etc. POP’s
are commonly called as Dirty dozen.
3. Heavy metals: The term “Heavy metals” appertain to the metallic
element which has a proportionally large density greater than 4 g/
cm3 and are poisoned or toxic even at very minute concentrations
However, as trace elements, they are essential to maintain the
metabolic reactions. They are dangerous for human health as they
bioaccumulative in nature; some heavy metals are lead, mercury,
cadmium, silver, nickel, vanadium, chromium, manganese etc.
4. Particulate matter: Particulate matter (PM) is a common term
used for a type of air pollutants, consisting of varying mixture of
particles suspended in breathing air, which va ry in size and
composition, and are produced by a wide variety of natural and
According to size distribution two types of aerosols have major
concern as air pollutants.
PM2.5 (Aerodynamic diameter smaller than 2.5 µm)
PM10 (Aerodynamic diameter smaller than 10 µm)
Air Quality Index: Government assistances uses the air quality index to
convey to the public that how polluted the air is at present or how polluted
it can become further. Rise in AQI causes the health threat to common
public. Different countries have their own air quality indices, similar to
different national air quality standards (NAAQs). The National Air Quality
Index (AQI) proposed in New Delhi on 17 September 2014 under the
Swachh Bharat Abhiyan and is outlined as ‘One Number-One Colour-
One Description’. There are 6 AQI categories, that are Good, Satisfactory,
Moderately polluted, Poor, Very Poor, and Severe. The Proposed AQI will
consider 8 pollutants (PM2.5, PM10 , SO2, NO2, CO, O3, NH3, and Pb) for
which short term (upto 24-hourly averaging period) National Ambient Air
Quality Standards are prescribed.
Table1. Air Quality Index (AQI) Categories, Ranges and their Health Impacts
AQI Air Pollution Level Health Implica tions
0-50 Good Minimal Impact
51-100 Satisf actory Slight breathing discomfort to sensitive people
101-200 Moderately polluted Sensitive groups of people may experience
201-300 Poor may cause breathing discomfort to people on
prolon ged ex po su re, and disc om fort to
persons with heart disease
301-400 Very Poor Health cautions of emergen cy conditions,
caus es respiratory illness to the people on
401-500 Severe Health ale rt : resp iratory imp act eve n on
healthy people and serious health impacts on
people with lung disease.
From past few decades, much of the work on air pollution has centred on a
small set of 6 pollutants, called criteria pollutants, that have been identified
as contributors to sulphurous and photochemical smog. EPA (Environmental
Protection Agency), USEPA has set national air quality standards for 6
criteria pollutants: ground level ozone, carbon monoxide, nitrogen dioxide,
sulphur dioxide, particulate matter and lead.
Table 2. National Ambient Air Qu ality Standards
Pollutants Time Concentration in Ambient Air
Average Industrial, Ecolog ically
Residen tial, Sensitive Area
Rural and (notified by
Other Areas Cen tral
Sulphur dioxide (SO2) (µg/m3) Annual* 50 20
24 hours** 80 80
Nitrogen dioxide (NO2) (µg/m3) Annu al* 40 30
24 hours** 80 80
3) Annual* 60 60
24 hours** 100 100
3) Annual* 40 40
24 hours** 60 60
Ozone (O3) (µg/m3) 8 hours* 100 100
1 hour** 180 180
Lead (Pb) (µg/m3) Annual* 0.50 0.50
24 hours** 1.0 1.0
Carbon monoxide (CO) (mg/m3) 8 hours* 02 02
1 hour** 04 04
Ammonia (NH3) (µg/m3) Annual* 100 100
24 hours** 400 400
Benzene (C6H6) (µg/m3) Annual* 5 5
Benzo(a)Pyrene (BaP) (ng/m3) Annu al* 1 1
Arsenic(As), ng/m3Annu al* 6 60
Nickel (Ni), ng/m3Annual* 20 20
Source: N ational Ambient Air Quality Standards, Central Pollution Control Board
notification in the Gazette of India. Extraordinary, New Delhi, 18th November, 2009.
Criteria Pollutants: Health impacts
The inhaled air pollutants have severe effects on human health
disturbing lungs and respiratory system; they are also taken up through the
blood and pumped all-round the body.
1. Nitrogen dioxide: The major sources of anthropogenic emissions
engines in vehicles and ships). The most important role of NOx is in
the formation of secondary pollutant like PAN (peroxy acetyl nitrate),
Tropospheric Ozone and Acetaldehyde. When NOx and volatile
organic compounds reacts in present of sunlight, they form
photochemical smog, a significant form of air pollution. Long span
exposure of NO2 causes bronchitis, reduced lung functions.
2. Sulphur dioxide: Sulphur dioxide has a sharp odour and is a
colourless gas. About 99% of sulphur dioxide in air arises from
anthropogenic source, and a very little quantity is released naturally
by volcanic activity. The leading anthropogenic source of SO2
the burning of sulfur-containing fossil fuels for domestic heating,
motor vehicles and power generation. The eventual outcome of all
sulphur in atmosphere is to be oxidized into sulphate ion. Enormous
concentration of sulfate aerosols in atmosphere causes global
dimming (Gradual decline in amount of global direct radiation). High
concentration of sulphur oxides reacts with fog (liquid aerosols)
resulted into Sulfurous smog, which causes severe consequence to
human beings. When SO2
acid; this is the foremost constituent of acid rain which is a reason
of deforestation. SO2
of the lungs, and causes irritation of the eyes, aggravation of asthma
and chronic bronchitis and makes people more prone to infections
of the respiratory tract. Hospital admissions for cardiac disease
and mortality increase on days with higher SO2
3. Ground level Ozone: Ground level Ozone or tropospheric ozone
is only 10 % of whole amount of ozone present in vertical column
in atmosphere however, this relatively small amount of tropospheric
ozone has great importance in the formation of photochemical smog,
formed by the reaction of pollutants such as nitrogen oxides (NOx)
and volatile organic compounds (VOCs) in the presence of sunlight
(photochemical reaction), As a result, the highest levels of ozone
pollution occur during periods of sunny weather. Ozone is a potent
oxidizing agent readily reacting with other chemical compounds to
make sever a l possib le toxic oxides. The greenhouse gas ,
Tropospheric ozone initiates the chemical elimination of methane
and other hydrocarbon from the atmosphere. Extreme ozone in the
air has a manifest outcome on human health and causes breathing
difficulties, elicit asthma, decrease lung functions, and lower our
resistance to colds and pneumonia.
4. Carbon Monoxide: Carbon monoxide (CO) is a colorless ,
odourless, tasteless, toxic air pollutant. The natural source is volcanic
actions and anthropogenic source is incomplete combustion of
carbon- containing fuels. CO has an indirect radiative effect by
elevating concentrations of methane and tropospheric ozone (O3).
The dominating sink of CO is reaction with OH radical. Around
80% CO is sinking by reacting with OH in the troposphere.
Breathing high concentration of CO (carbon monoxide) leads to
react with haemoglobin due to its more affinity towards haemoglobin
than oxygen (O2) which leads to formation of Carboxyhemoglobin
(COHb). The binding of CO with other haeme proteins causes
changes in the function of the affected organs such as the brain
and the cardiovascular system, and also the developing foetus. It
can weaken our concentration, slow our reflexes.
5. Lead: Pb is a toxic heavy metal that is widely used in different
industries. Both indoor and outdoor sources may result into Pb
pollution. It is emitted from motor engines, particularly with those
using petrol containing Pb tetraethyl, smelters and battery plants,
as well as irrigation water wells and wastewaters, are other
emission sources of the Pb into the environment. Prolonged exposure
of Pb can cause digestive problems, impairment to the nervous
system, and in some cases cause cancer. It is especially hazardous
to small children.
6. Particulate matter: Particle pollutants are most important parts
of air pollutants. They are mixture of particles found in the air.
Particle pollution is known as PM is associated with most of
pulmonary and cardiac-associated morbidity and mortality. They
have varied in size rangin 2.5
PM10). The size of particle pollutants is directly linked with the
onset and progression of the lungs and heart diseases. Smaller size
particles reach the lower respiratory tract thus have superior
potential for instigating lungs and heart diseases. Also, various
scientific data have validated that fine particle pollutants cause
premature death in people with heart and lung disease comprising
cardiac dysrhythmias, aggravated asthma and nonfatal heart
attacks. On the basis of level of exposure, particulate pollutants
cause mild to severe illnesses. Wheezing, cough, dry mouth, and
breathing complications are the most dominant clinical indications
of respiratory disease ensued from air pollution.
International Standards: World Health Organization’s “WHO Air quality
guidelines” offer global assistance on threshold limits for 4 key air pollutants
that causes health threats- particulate matter (PM), ozone (O3), nitogen
dioxide (NO2) and sulphur dioxide (SO2).
Table 3. Guideline levels for pollutants (µg/m3)
Pollutants Time period Concentration (µg/m3)
PM 2 .5 Annual mean 10
24-hour mean (99th percentile) 25
PM 1 0 Annual mean 20
24-hour mean (99th percentile) 50
O38 h, daily maximum 100
NO2Annual mean 40
1 h mean 200
SO224-hour mean 20
10-min mean 500
Source: World health organization A ir qua lity guidelines, 200 5
Practical measures to reduce air pollution
Using fuels with low sulphur and ash content and unleaded petrol.
Use of public transport.
Sensitive locations (schools, hospitals, playgrounds etc.) should not
be located along the busy paths.
Vegetation cover should be improved along the roadside.
Industries and waste dumping sites should preferably be located in
the outer edge of the city.
Fig. 1 Controlling measures of air pollutants in industrial establishments
The industrialization and modernization is necessary to grow, but a
long-term ecological impact and health problems of such growth should
always be considered prior to imposing a large economic load on the societies.
Therefore, it is recommended to maintain stability between economic
development and air pollution by authorizing policies to control all the actions
that results in air pollution.
CONCLUSIONS AND RECOMMENDATIONS
This review presents the adverse impacts of air pollutants on human
health, triggering, numerous ailments leading to high morbidities and
mortalities, predominantly in the developing countries. Therefore, in view
of greater exposure of diverse pollutants in humans, dietary interventions
such as organic foods derived from plants, may protect different organs
from their effects. Air pollution control is need of the hour and should be on
the topmost priority of the governments. The policy makers in developing
countries must update all the laws and regulations associated to air pollution
so that general public can be helped in this regard as for as possible. A
powerful environmental protection organization must be leaded to coordinate
among different departments for combating air pollution. An operative
environmental protection organization should have enough budgets for
administration, monitoring, research and development to have full control
on the environment related problems including air pollution.
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