The dominant greenhouse gas responsible for 42% of total RF on the best estimate scale. Of this around 20% (8.6% of total) is not from fossil fuels but the burning of and loss of forest for sourcing of building materials and the creation of agricultural land, in some cases to grow biofuels (IPCC, 2013).

The implications of CO2 emissions are far reaching and are thought to be one of the leading factors for the current refugee crisis affecting the middle east and Europe (Gleick, 2014)(Kelley et al., 2015).

IPCC, 2013. IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge.


Ozone (O3) is not emitted directly into the air, but is a photochemical pollutant. Virtually all of it is formed by chemical reactions involving primarily Nitric Oxide (NO), Nitrogen Dioxide (NO2), Non-methane Volatile organic compounds (NMVOCs), Methane (CH4) itself a VOC and Carbon Monoxide (CO). Ordinarily O3 would be kept in check by the titration reaction, whereby excess NO reacts with O3 to form NO2 and O2. However excess NMVOC concentrations have altered this balance allowing NO to produce NO2 without consuming O3 (EEA 2013).

Ozone across europe

Accumulated ozone exposure values, over a threshold of 40 parts per billion, for crops (AOT40c) increase from Northern Europe towards the South Mediterranean countries. Taken from EEA 2015.

Health Effects

Can causes inflammation in the lungs and bronchia decreasing lung function and aggravating asthma and other lung diseases, leading to premature death (EEA 2013). A 1% increase in O3 emissions has been associated with a 0.1% increase in Asthma admissions to hospital (Janke, 2014). One study has found a link between Maternal exposure to Ozone and the child developing Type 1 diabetes (Malmqvist et al., 2015).

Environmental Effects

Ozone is powerful, aggressive and reduces plant uptake of CO2, biodiversity and crop yields. Also alters ecosystem structure, impairs reproduction and stunts growth (EEA 2013) (EEA 2014). Increased concentrations of ozone in the air are associated with reductions in Nitrogen fixation (Hewitt et al., 2015).
Globally it is estimated that in the year 2000 total yield losses for the three main staple crops were 3.9–15% for wheat, 8.5–14% for soybean, and 2.2–5.5% for maize as a result of O3 (Avnery et al., 2011).

Climate Effects

Ozone is a greenhouse has contributing to warming of the atmosphere (EEA 2013).
A short lived trace gas with an average lifespan of only a few weeks (23 days) in the atmosphere (Edenhofer 2014).


A Well Mixed Green House Gas (WMGHG). Anthropogenic sources of CH4 account for around 65% of the global emissions in the period since 2000. This includes rice paddies, agriculture, ruminant animals, sewage and waste, landfills and fossil fuel extraction (IPCC, 2013).

IPCC, 2013. IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge.

Nitrous Oxide N2O

A Well Mixed Green House Gas (WMGHG). Three main anthropogenic sources of N2O are the Haber-Bosch process, the cultivation of legumes and crops increasing Biological Nitrogen Fixation (BNF) and the combustion of fossil fuels which converts atmospheric N2 into NOx and is re-desposited on the earth (IPCC, 2013).

IPCC, 2013. IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge.


Nitrogen dioxide is a reactive gas that is mainly formed by oxidation of nitrogen monoxide (NO). High temperature combustion processes (e.g. those occurring in car engines and power plants) are the major sources of NO and NO2. These two gases are collectively known as NOX. Nitrogen monoxide accounts for the majority of NOX emissions. A small part of NOX emissions is directly emitted as NO2, typically 5–10 % for most combustion sources. There are clear indications that for traffic emissions the direct NO2 fraction is increasing significantly due to increased penetration of diesel vehicles, especially newer diesel vehicles (Euro 4 and 5). This may lead to more frequent breaching of the NO2 limit values in traffic hotspots (EEA, 2013).

The European Environment Agency puts the costs of NOx emissions (primarily NO2) at between €8681 and €24442 per tonne of emissions in Austria. In the UK the equivalent to 23,500 deaths are thought to be related to NO2 pollution (Defra, 2015).

Health Effects

NO2 can affect liver, lung, spleen and blood. Can aggravate lung diseases, leading to respiratory symptoms and increased susceptibility to respiratory infection (EEA, 2013). A 1% increase in NO2 emissions has been associated with a 0.1% increase in Asthma admissions to hospital (Janke, 2014) reduced adolescent lung function (McBride, 2015), possible systemic autoimmune rheumatic disease (Bernatsky et al., 2015), Prostate cancer (Parent et al., 2013) and for every 5ppb increase in NO2 the post menopausal breast cancer risk increased by 25% (Crouse and Goldberg, 2010), Type 1 Diabetes (Malmqvist et al., 2015) and minor congenital malformations (Landau et al., 2015).

Environmental Effects

Contributes to the acidification and eutrophication of soil and water, leading to changes in species diversity. Acts as a precursor of ozone and particulate matter, with associated environmental effects. Can lead to damage to buildings (EEA 2013) (EEA 2014).

Climate Effects

Contributes to the formation of ozone and particulate matter, with associated climate effects (EEA, 2013).

Carbon Monoxide CO

Carbon monoxide is a gas emitted due to incomplete combustion of fossil fuels and biofuels. Road transport was once a significant source of CO emissions, but the introduction of catalytic converters reduced these emissions significantly. CO concentrations tend to vary with traffic patterns during the day. The highest CO levels are found in urban areas, typically during rush hours at traffic locations. The largest CO emission sector is now commercial, industrial and household fuel combustion, where CO is unregulated (EEA, 2013).

It was not possible to find any external cost data for CO emissions.

Health Effects

CO enters the body via the lungs. It is absorbed into the blood, where it is strongly bound to haemoglobin.
In already sensitive people, such as those with heart and lung problems, CO exposure affects the already compramised ability of their bodies to respond to increased oxygen demands of exercise or exertion.
Can itself lead to heart disease and damage to the nervous system, can also cause headache, dizziness and fatigue (EEA, 2013). CO is of particular interest as it is a known neurotoxin and potential public health threat. It can cross the placenta during pregnancy and adversely affect the developing brain of the foetus. Currently policy and risk evaluation is mostly based on studies on adults (Levy, 2015). Studies have also suggested a link between stroke and CO exposure (Bell et al., 2009) and seems to be more prevailent for ischemic stroke and in the Asian population (Yang et al., 2014). In some cases the association was negative (i.e. CO lowers the risk)(Tian et al., 2015) and has also been associated with lower inflammation (Zhao et al., 2015) particularly under controlled conditions (Queiroga et al., 2009).

Environmental Effects

Precursor of ozone. May also affect animals in the same way as humans (EEA, 2013) (EEA 2014).

Climate Effects

An atmospheric lifespan of around three months. Contributes to the formation of greenhouse gases through slow oxidisation into CO2, forming ozone in the process (EEA, 2013).


Non methane volatile organic compounds (NMVOCs) is one of the precursor gases to tropospheric ozone (O3), aerosol formation and the lifetime of CH4 (IPCC, 2013). It generally only lasts at maximum a few months in the atmosphere (IPCC, 2013), meaning emissions reductions have immediate and noticable effects on RF. Trends indicate a general decline in emissions in the region of a few percent to more than 10% over North America and Europe. However formaldehyde column abundances over North Eastern China and India have shown increases from 1997 to 2007 (IPCC, 2013). Global NMVOC measurement coverage is generally poor except for a few compounds (IPCC, 2013).


Sulphur dioxide is emitted when fuels containing sulphur are burned. The key man made contributions to ambient SO2 derive from sulphur containing fossil fuels and biofuels used for domestic heating, stationary power generation, and transport. Volcanoes are the most important natural source (EEA, 2013).

Human Health Effects

Aggravates asthma and can reduce lung function and inflame the respiratory tract. Can cause headache, general discomfort and anxiety (EEA, 2013).

Environmental Effects

Contributes to the acidification of soil and surface water. Causes injury to vegetation and local species losses in aquatic and terrestrial systems. Contributes to the formation of particulate matter with associated environmental effects. Damages buildings (EEA, 2013)(EEA 2014).

Climate Effects

Sulphur oxides actually have a cooling effect on the earth (EEA, 2013) as they block out the sun through hazyness in the sky (sulphate particles).
Volcanic activity has been highlighted as one of the reasons global temperatures have not soared as much as expected (Ridley et al., 2014).


Particulate matter is the general term used for a mixture of particles (solid and liquid) suspended in the air, with a wide range of sizes and chemical compositions. PM2.5 refers to ‘fine particles’ that have a diameter of 2.5 micrometres (μm) or less. PM10 refers to particles with a diameter of 10 (μm) or less (see Figure 2.1). PM10 includes the ‘coarse particles’ fraction in addition to the PM2.5 fraction (EEA, 2013).

Human Health Effects

Cardiovascular and lung diseases, heart attacks and arrhythmia’s, central nervous system, systemic autoimmune rheumatic diseases (Bernatsky et al., 2015) and reproductive system effects. Can cause cancer, notably lung cancer (Raaschou-Nielsen et al., 2013) and lead to premature death (EEA, 2013). In the USA it is thought a reduction of 3.9 μg/m³ would prevent 7978 heart failure hospitalisations and save $300million a year (Shah et al., 2013). A study of 367,251 patients in europe found an increased Hazard ratio of 1.07 per 5 μg/m³ (Beelen et al., 2014). In the UK the effect on mortality is thought to be equivalent to 29,000 deaths every year (Defra, 2015). There is no recognised safe level of PM (WHO, 2013).

Environmental Effects

Affects animals in the same way as humans. Plant growth and ecosystem processes adversely affected. Can cause damage and soiling of buildings and reduces visability (EEA, 2013) (EEA, 2014).

Climate Effects

Some PM lead to cooling and others lead to warming. BC is thought to be responsible for around 18% of total positive RF, primarily through darkening the surfaces of snow and ice covered areas. Can alter rainfall patterns (EEA, 2013).

Europe map PM2.5v5
Map showing number of deaths attributed to PM2.5 pollution per million of population in 2011. Original data from EEA, 2014, Figure created by wattsthecost.info

Lead Pb

Lead was brought into the spotlight in the 90’s when its health effects were recognised resulting in its elimination from petrol. Inhalation exposure may be significant when Pb levels in the air are high. Elevated exposures are generally due to local sources rather than being the result of long‑range transport from remote sources. However, air pollution may contribute significantly to the Pb content of crops, through direct deposition. Although uptake via plant roots is relatively limited, rising Pb levels in soils over the long term are a matter for concern and should be addressed because of the possible health risks of low-level exposure to Pb (EEA, 2013). Lead is thought to have been responsible for a global crime wave in the 90’s, the cost of which is unknown (Monbiot, 2013)(Casciani, 2014).

Lead Cost
Estimated cost in Euros of lead emissions from electricity production in 2013 across the EU22

Health Effects

Lead is a neurotoxic metal that also accumulates in the body and damages organs, such as the kidneys, liver, brain, and nerves. Exposure to high levels of Pb causes serious brain damage, including mental retardation, behavioural disorders, memory problems and mood changes. Impairment of neuro-development in children is the most critical effect. Exposure in utero, during breastfeeding, or in early childhood may lead to such health problems. Lead accumulates in the skeleton which is potentially dangerous during pregnancy. Hence, previous exposure to a woman before she becomes pregnant is important in determining the health of her child (EEA, 2013).

Environmental Effects

Lead bio-accumulates and adversely impacts both terrestrial and aquatic systems. As with humans, the effects on animal life include reproductive problems and changes in appearance or behaviour (EEA, 2013).

Cadmium Cd

Cadmium is highly ‘persistent’ in the environment and bioaccumulates. In heavily contaminated areas, resuspended dust (caused by vehicles or wind blowing cadmium particles off the ground) can constitute a substantial part of the exposure for the local population. In Europe, air pollution and fertilisers (both mineral and organic) contribute almost equally to annual exposure. Both of these increase the relatively large accumulations of Cd in topsoil, thereby increasing the risk of future exposure through food. The levels of Cd in non-smokers have not decreased over the last decade (EEA, 2013).

Estimated total cost in Euros of Cadmium pollution from electricity production in 2014 across the EU22

Human Health Effects

The kidneys and bones are the critical organs affected by chronic environmental exposure to Cd. The main effects of this exposure include impaired kidney function and increased risk of osteoporosis. An increased risk of lung cancer has also been reported following inhalation exposure to Cd.

Environmental Effects

Cadmium is toxic to aquatic life as it is directly absorbed by organisms in water. It interacts with cellular components, causing toxic effects in the cells of all organisms.

Mercury Hg

The largest anthropogenic source of Hg emissions to air on a global scale is the combustion of coal and other fossil fuels. Others sources include metal production, cement production, waste disposal and cremation. In addition, gold production makes a significant contribution to global air emissions of Hg. The main natural sources of Hg emissions are diffusion from the Earth’s mantle though the lithosphere, evaporation from the sea surface and geothermal activity. Mercury emitted in inorganic forms is converted biologically to methyl mercury in soil and water (EEA, 2013).

Mercury Cost
Estimated external cost of Mercury emissions from EU22 electricity production in 2013 (€)

Human Health Effects

Mercury can damage the liver, the kidneys and the digestive and respiratory systems. It can also cause brain and neurological damage and impair growth. Methyl mercury is a potent neurotoxin. Unborn children are the most vulnerable population group in terms of exposure to Hg (EEA, 2013)(EEA 2014).

Environmental Effects

Mercury bioaccumulates and adversely impacts both terrestrial and aquatic systems. It can affect animals in the same way as humans and is very toxic to aquatic life (EEA, 2013).

Arsenic As

Arsenic is released into the atmosphere from both natural and anthropogenic sources. Most man-made emissions are released from metal smelters and the combustion of fuels. Pesticides used to be an important source of As, but restrictions in various countries have reduced its role. Tobacco smoke may contain As, making it a source of As exposure in ambient air. Arsenic in the air is usually a mixture of atomic As and arsenate (AsO4 3- a compound that combines arsenic and oxygen), with organic As compounds. These organic varieties are usually of negligible importance except in areas where there is substantial application of methylated As pesticides (EEA, 2013).

Arsenic Cost

Human Health Effects

The non-cancerous effects of inhaling air with high As levels include increased mortality from cardiovascular diseases, neuropathy, and gangrene of the extremities. There is evidence that inorganic As compounds cause cancer of the skin and lungs in humans. Lung cancer is the critical effect following exposure by inhalation (EEA, 2013).

Environmental Effects

Arsenic is highly toxic to aquatic life and also very toxic to animals in general. Plant growth and crop yields may be reduced where soil As content is high. Organic As compounds are very persistent in the environment (they are not broken down over time by environmental processes) and bioaccumulate in the food chain (EEA, 2013) (EEA 2014).

Nickel Ni

Nickel occurs in soil, water, air and in the biosphere. Nickel emissions to the atmosphere may come from natural sources such as windblown dust, volcanoes and vegetation. The main anthropogenic sources of Ni emissions into the air are combustion of oil for the purposes of heating, shipping or power generation; Ni mining and primary production; incineration of waste and sewage sludge; steel manufacture; electroplating; and coal combustion.

Nickel Cost
Estimated cost of Nickel emissions from EU22 electricity production in 2013 (€)

Human Health Effects

Nickel exposure can result from breathing ambient
air. In very small quantities Ni is essential to
humans. However, a large uptake can be a danger
for human health as several Ni compounds are
carcinogenic (EEA 2014), increasing the risk of developing,
for example, cancers of the lung, nose, larynx or
prostate. Non‑cancerous effects on health include
allergic skin reactions (generally not caused by
inhalation), disruption of endocrine regulation, and
damage to the respiratory tract, and the immune
systems. The most common harmful health effect of
Ni in humans is an allergic reaction. Approximately
10–20 % of the population is sensitive to Ni (EEA, 2013).

Environmental Effects

As is the case for humans, Ni is an essential
element for animals in small amounts. But in high
concentrations, Ni and its compounds can be
acutely and chronically toxic to aquatic life and
may affect animals in the same way as humans. It
is known that high Ni concentrations in sandy soils
can damage plants, and that high concentrations
in surface waters can diminish the growth rates of
algae. Microorganisms can also suffer from growth
decline. Nickel is not known to accumulate in plants
or animals (EEA, 2013).

Benzene C6H6

Human Health Effects

Associated with accelerated mortality (Beelen et al., 2014). Is Carcinogenic (EEA 2014).

Environmental Effects

Bioaccumulates, especially in invertebrates. Acute toxic effects on aquatic life. Leads to reproductive problems, changes in appearance and behavioral changes. Causes damage to leaves of crops and can kill plants (EEA 2014).

Climate Effects

Benzene might give a small contribution to RF as it contributes to the formation of ozone and secondary organic aerosols.

Benzoapyrene BaP

Part of the Polycyclic Aromatic Hydrocarbon (PAH) family. Emissions of Benzo(a)pyrene (BaP) have increased by around 20% across the EU between 2003 and 2012, mainly as a result of commercial, institutional and household fuel combustion (EEA, 2014).

Human Health Effects

Linked to increased levels of white blood cell DNA adducts, which correspond to DNA damage (IARC, 2013), Rare sarcomas (Charbotel et al., 2014) and bladder cancer (Ferrís et al., 2013).

Envirnomental Effects

Toxic to birds and aquatic life. Bioaccumulates, particularly in invertebrates (EEA 2014).



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