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Air pollutants: Particulate Matter

What is particulate matter?

Particle pollution, also called particulate matter (PM), atmospheric aerosol particles or suspended particulate matter (SPM), is defined as microscopic solid (almost always) or liquid materials floating in the air.

particulate matter

Types of particulate matter

Those airborne particles can be divided in suspended particulate matter, thoracic particles, respirable particles, inhalable coarse particles and soot. Inhalable coarse particles can also be classified depending on their size as:

  • Coarse Particles (PM10): aerodynamic diameter from 2.5 to 10 micrometers (µm). To give you an idea, its size is like 1/5 part from a human hair or 1/9 part from a fine beach sand particulate.
  • Fine Particles (PM2.5): 2.5 µm or smaller. For example, it is as little as 1 part from 20 of a human hair, so it is obvious that these particulates can only be seen with an electron microscope.
  • Ultra fine particles (UFPs): less than 100 nanometres (nm). Since they are far smaller, there is no regulation for this size class, even though these are considered to have more severe health impact than the others.

Sources and composition of particulate matter

The composition of particles depends on its origin and formation. Aerosols can occur naturally or artificially.


Most common natural aerosols are pollen or fog, although other natural sources can be volcanoes, sand storms, forest and grassland fires, living vegetation and sea spray.

Human activities such as the burning of fossil fuels, different industrial activities and power plants contribute to produce a significant amount of artificial aerosols. Haze, dust, smoke are just some examples, but there are many more particulate air pollutants.

Since there is a wide range of aerosols’ compositions, here you have summarized some examples:

  • Mineral dust: made of mineral oxides blown from Earth’s crust.
  • Sea salt: originated from sea spray and composed by sodium chloride.
  • Sulfuric acid and nitric acid: generated in the oxidation of primary gases such as sulfur and nitrogen oxides.
  • Organic Matter (OM): deriving from the oxidation of VOCs.

What are the health and environmental effects of particle pollution?

Their capacity to penetrate deeply into your lungs makes particulate matter one of the criteria pollutants to control in order to protect humans’ wellness and health. The smaller the particle is, the more harmful it can be for the organism. This is why particulate matter have different degrees according to its penetration capability into the cardiovascular system:

  • Inhalable particles: can penetrate into the bronchi and are filtered by the cilia.
  • Thoracic particles: can reach easily the bronchioles.
  • Respirable particles: if thoracic particles can even pass throw the alveoli until the bloodstream, then are considered respirable particles.

respiratory diseases

All those particles have effects on humans health, damaging your lungs and your circulatory system. The most common long-term health effects caused by the inhalation of particulate matter are: asthma, lung cancer, reduced lung function, respiratory diseases, cardiovascular diseases, premature delivery and birth defects (such as low birth weight and premature death).

Exposure to fine particles in the short-term can cause coughing, sneezing, runny nose, shortness of breath and eye, nose, throat and lung irritation.

Huge concentrations of particles in the air can lead to haze creation or difficulties in the photosynthesis functions of plants. Furthermore, depending on their composition they can react with other compounds to create other harmful gases for the environment or and the people.

How is particulate matter air pollution controlled?

Over the years, developed countries have reached some agreements to control pollution. Each country or state has its own implementation plan. For example, the Clean Air Act made by the U.S. Environmental Protection Agency (EPA) establishes National Ambient Air Quality Standards (NAAQS) for those criteria pollutants considered most harmful for health and the environment. Another example is the European Union Air Quality Directive by the European Environmental Agency, which also establishes some standards and tips to reduce air pollution, both indoors and outdoors.

Both sizes of particulate matter, PM10 and PM2.5, are classified as a primary and secondary criteria pollutants since it can be extremely harmful for all living beings. Maximum permitted or recommended levels for PM are:

  • In PM2.5:
    • World Health Organization (WHO) guidelines: 25 μg/m³ per day (which cannot be exceeded more than 3 days/year) and 10 μg/m³ per year.
    • NAAQS: maximum concentration of 35 μg/m³ daily and annual mean of 12 μg/m³.
    • EU Air Quality Directive: only monitoring annual concentration, which cannot be higher than 25 μg/m³.
  • In PM10:
    • World Health Organization (WHO) guidelines: 50 μg/m³ per day (which cannot be exceeded more than 3 days/year) and 20 μg/m³ per year.
    • NAAQS: 150 μg/m³ and can only be exceeded more than once per year on average over 3 years.
    • EU Air Quality Directive: cannot exceed more than 35 times annually the concentration of 50 μg/m³ every 24 hours. There is also a maximum of 40 μg/m³ per year.
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Air pollutants: Lead

What is lead pollution?

Lead (Pb) is a naturally occurring heavy metal that is found in the Earth’s crust. It is denser than most common materials, soft, malleable and has a low melting point. This capability to change easily the state from solid to liquid at atmospheric pressure is favouring its facility of being introduced as an air pollutant into the atmosphere.


How does lead get into the air?

Major sources of lead in the air are mining, metal manufacturing and piston-engine aircraft operating on leaded aviation fuel. Other sources of lead air pollution are industrial productions, waste incineration, recycling, mobilization of previously buried lead, utilities and lead-acid battery manufacturers.

Peak of lead emissions to the atmosphere had place during Industrial Revolution and with the usage of leaded gasoline during the last decades of the 20th century. Nowadays, high lead emissions still have place, especially in developing countries where industrial emissions arising from coal burning prevail.

lead manufacture

What are the environmental and health effects of lead pollution?

Lead has not as much influence on the environment as other pollutants, but it can have a noticeable impact on plants. Lead accumulate on soils for a long time (hundreds or even thousands of years) and also can combine with other metals to inhibit photosynthesis. At high lead pollution levels, plants growth and survival may suffer adverse effects and can cause neurological problems to vertebrates.

Lead air pollution health effects on humans usually are neurological effects in children and cardiovascular effects (high blood pressure and heart disease, for example) in adults.

Lead exposure on humans can be very harmful, involving almost every organ and system in the human body. Once it is inhaled, lead is placed on the bloodstream and bones driving to a possible case of lead poisoning.  

cardiovascular problems

Lead poisoning: symptoms and treatment

Apart from air pollution, lead poisoning come from different sources, such as water, dust, food or consumer products. The effects it may cause to each individual depends on the levels and the time exposure to the pollutant.

Some lead poisoning symptoms or signs that could indicate you are in danger are: headache, intermittent abdominal pain, loss of appetite, nausea, diarrhea, constipation, memory loss, kidney failure, male reproductive problems, depression, weakness, pain or tingling in the extremities and muscles.

In children, lead poisoning is prone to cause similar symptoms: loss of appetite, abdominal pain, vomiting, weight loss, constipation, anemia, kidney failure, irritability, lethargy, learning disabilities and behavioral problems. Others such as slow development of normal childhood behaviors (like the usage of words and talking) and permanent neurological problems (like learning deficits and lowered IQ) are also commonly diagnosticated to this segment. During the pregnancy, breathing lead polluted air may increase the risk of premature birth or low birth weight.

According to the level of poisoning and what part of your organism is affected, treatments may change. We will have a look to lead poisoning treatments due to air pollution.

When lead levels are high on blood, lead intoxication can be treated with chelation therapy or treatment of iron, calcium and zinc deficiencies, as these are treatments related to lead absorption.

How is lead air pollution controlled?

Over the years, developed countries have reached some agreements to control pollution. Each country or state has its own implementation plan. For example, the Clean Air Act made by the U.S. Environmental Protection Agency (EPA) establishes National Ambient Air Quality Standards (NAAQS) for those criteria pollutants considered most harmful for health and the environment. Another example is the European Union Air Quality Directive by the European Environmental Agency, which also establishes some standards and tips to reduce air pollution, both indoors and outdoors.

Lead is considered both a primary and a secondary criteria pollutant due to its effects either on public health and the environment. Maximum permitted or recommended levels of lead in the air are:

  • Nothing is included in the World Health Organization (WHO) guidelines.
  • NAAQS: cannot exceed 0,15 μg/m³ for 3 months average.
  • EU Air Quality Directive: cannot exceed 0,5 μg/m³ over a year.
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Health effects of air pollution on humans

health effects of air pollution

World population emits huge amount of air pollutants every day, and this negatively affects our health. These emissions increase every year, threatening the planet and one of our most important sources of life, the air.

Air pollution consequences on the environment are well-known, and if you still want to know more about it check out or posts on this topic. However, it is little known that molecules that form air pollutants have serious impact on our well-being, as these affect several parts of our organisms.

It doesn’t matter how healthy you are when it comes to air pollution. However, sensitive groups such as children, elderly and people with respiratory or heart diseases may experience stronger symptoms and health effects.

Respiratory problems

Since our respiratory system is based in the interaction between our body and external air, it is obviously highly affected when it comes to breathing air pollution. Short-term exposure to air pollution may drive to the following symptoms:

  • Eye and nose irritation
  • Chest pain
  • Pneumonia
  • Bronchitis
  • Asthma
  • Emphysema
  • Worse respiratory illnesses such as bronchitis, asthma or emphysema.
  • Coughing or wheezing
  • Throat irritation
  • Nose bleeding
  • Dizziness
  • Weakness
  • Headache
  • Confusion
  • Fatigue
  • Nausea
  • Airway inflammation
  • Reduce lung function
  • Harm lung tissue
  • Shortness of breath (dyspnea)
  • Decrease the capacity to perform exercise
  • Premature mortality due to cancer or respiratory disease
  • Kidney failure
  • Male reproductive problems
  • Depression
  • Diarrhea

Long-term exposure to air pollution can cause consequences of suffering the health issues mentioned above stronger, they can even become chronic illnesses. Apart from those, other health problems in cases of constant exposure to air pollution are memory loss, movement problems, cardiovascular and neurological issues or even dead.

Cardiovascular and heart problems

If the pollutants inhaled have the capability to penetrate deeply enough into the human body to reach the bloodstream, consequences may turn into a huge amount of health problems. Moreover, the person will experience fast and direct effects since it reduces the amount of oxygen arriving to organs, or in other words, worse quality and less blood production.

Mobility issues, muscular problems, high blood pressure or heart diseases can be diagnosticated in cases of lead or carbon monoxide poisoning. Other important pollutants directly related to the cardiovascular system are sulfur dioxide (SO2) and nitrogen dioxide (NO2).

Neurological and birth problems in kids and other issues in adults

As mentioned above, children are more vulnerable to air pollution effects, such as anemia or behavioral problems. Mothers breathing high concentrations of polluted air during the pregnancy reach the fetus and experience issues like low birth weight or premature birth. Moreover, it can carry future consequences, for example permanent neurological problems (like learning deficits and lowered IQ) or slow development of normal childhood behaviors (like the use of words and talking).

baby sleeping

Inhaling airborne particles also affects the neurological system of adults, for example increasing the risk of alzheimer and damaging or weakening the immune system. On the other hand, breathing volatile organic compounds (VOCs), is related to liver, kidney and central nervous system damages.

Skin issues

Air pollution can also damage your skin in several ways. However, its influence is not directly related since skin problems are given by the interaction between human-beings and environmental adverse conditions due to air pollution.

We may suffer skin cancer or premature aging skin because of ultraviolet sunlight rays high exposure, driven by the ozone layer depletion. Furthermore, skin irritation can be experienced when bathing in eutrophic water, if the water contains certain kinds of algaes. Both events result from air pollution emissions to the atmosphere and its posterior indirect effect on humans and the environment.

Sources of health effects of air pollution

Those evidence and effects in the human body can be given by adverse environmental conditions or either airborne pollutants:

  • Smog: Since its gases-particles composition makes it easy to penetrate deeply in the body.
  • Ozone layer depletion, global warming and climate change: Exposing ourselves to more ultraviolet sun rays that can directly damage our skin and worse the air we breathe, with wildfires smoke for example.
  • Sulfur dioxide (SO2) and Nitrogen oxides (NOx): The main components of acid rain. They can also react in the atmosphere in order to become more harmful pollutants, in particular nitrogen dioxide (NO2).
  • Carbon monoxide (CO): As it reduces the amount of oxygen that can be transported in the bloodstream.
  • Lead (Pb): Once it is inhaled, it is placed on the bloodstream and the bones involving almost every organ and system in the human body.
  • Ozone (O3): This gas become so toxic at ground levels.
  • Particulate Matter (PM): The smallest the particle is, the deeper it may penetrate into our organism, even to the bloodstream.
  • Volatile Organic Compounds (VOCs): Especially highly concentrated indoors since its emissions can be produced by a big amount of daily use gadgets.
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Effects of air pollution on the environment: animals, plants and ecosystems

Human activities have increased the amount of pollutants introduced in the air, that have direct and indirect effects in almost every ecosystem. Air pollution can lead to harmful consequences for living organisms through the inhalation of pollutants adverse weather conditions and others.

How does air pollution affect animals’ health?

effects of air pollution on animals

No matter what their size is, air pollution affects almost every species on this planet. The most common health effects on animals are respiratory problems, which is totally obvious since they have similar respiratory systems to humans. Wildlife is prone to suffer same symptoms and diseases than humans. Specifically, lung tissue is very commonly affected on animals after breathing polluting gases or particles.

Most common symptoms and problems animals may suffer are:

  • Smog is composed of particles and gases, what makes it easy to penetrate deeply into the body, damaging the lungs and causing respiratory problems. Toxic environments are created with hard breathing adaptability. Furthermore, pollutants such as carbon monoxide can also lead to huge respiratory issues on animals.
  • Despite eutrophication influence is mainly to the ecosystem, due to certain toxic algae production some animals can suffer symptoms like skin irritation or health problems if drinking it.
  • Neurological issues on vertebrates because of lead accumulation on soils and its effects on plants.

How does air pollution harm plants and vegetation?

Air pollution has a lot of influence on vegetation by attacking its growth sources, such as airborne molecules, soil minerals or directly its organisms. Depending on the particular pollutant or environmental pollution conditions, main effects can be:

  • Smog, as well as particulate matter high concentrations, reduce the amount of sun rays arriving to plants, denying or slowing plant growth. This kind of air pollution damages forests and crops, especially vegetables such as soybeans, wheat, tomatoes, peanuts and cotton.
  • Ozone layer depletion increases the amount of UVB arriving to plants, and despite being prepared and adaptable to increasing levels of UVB, it can cause problems and modifications like form changes, nutrients distribution, developmental phases timing and secondary metabolism.
  • Forest and plants can also be harmed by acid rain since it damages tree’s leaves, robs the soil of essential nutrients and makes it hard for trees to take up water. All these issues imply growth and photosynthesis difficulties and more vulnerability to insects, diseases or bad weatherHigh concentrations of SOx are also harmful for vegetation foliage and growth, and can contribute to formate acid rain. Ozone also produce similar symptoms, especially during the plants growing season.
  • Lead can accumulate on soils for a long long time (hundreds or even thousands of years) and by combination with other metals it can inhibit photosynthesis, what implies growth and survival issues for the surrounding vegetation.
  • Nitrogen is essential for plants nutrition, but high levels of nitrogen dioxide or nitrogen monoxide pollution damage their lives.

ecosystem pollution

How changes in ecosystems affect the fauna and flora?

Last but not least, air pollution may lead to harm an ecosystem as a whole and not only a particular organism from it. Some clear examples are:

  • Marine ecosystems may experience high temperatures and exposure to UVB, reducing survival rate of phytoplankton and damaging early developmental stages of fish, shrimp, crab, amphibians and other marine animals. These effects are the result from the ozone layer depletion.
  • Global warming is changing some ecosystems faster than the capability of animals and plants to adapt, leading to possible extinction of a huge amount of species. For example, ice sheets inhabited by polar bears are disappearing, (as it was said) warming oceans, more extreme weather conditions, etc.
  • Due to the rising amount of carbon dioxide emissions and acid rain generation, the surface of oceans and water bodies has increased its acidity. This phenomenon is called ocean acidification and can lead to harmful consequences, such as depressing metabolic rates in jumbo squid, depressing the immune responses of blue mussels, and coral bleaching. Furthermore, ocean and lakes acidification makes water toxic to crayfish, clam, fish, and other aquatic animals. However, it can be good for some species as a trade-off, such as sea star, which increases its growth rate with highest water acid levels.
  • Eutrophication, formed by phosphorus and nitrogen concentrations in water bodies, can even change the entire ecosystem from water to land (in extreme cases). Toxicity of the water, reduced amount of oxygen in deeper layers and difficult adaptability to the new substances may cause several damages into indigenous fauna and flora, leading to their reduction or even extinction.
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Air pollution effects: Smoke + Fog = Smog

What is smog?

smog air pollution

Smog is an air pollution phenomenon that can be defined as the combination of various gases with dust and water vapor. In other words, smog is a yellowish or blackish fog composed of nitrogen oxides, sulphur oxides, ozone, smoke and dirt particles. This kind of visible air pollution was originally named in the early 20th century as a mixture of the words smoke and fog.

Types of smog

Depending on its origin and composition, there are 3 types of smog:

  • Volcanic smog is composed by oxygen, moisture, sunlight, particles and gases released from a volcano eruption. This type of smog is commonly seen in the Hawaiian Islands, as the Kilauea volcano has been erupting every day since 1983.
  • Photochemical smog is the most popular kind of smog nowadays. It is formed by nitrogen oxide, hydrocarbons and sunlight.
  • Sulfurous smog is originated when a high concentration of sulfur oxides are released into the atmosphere. It is also known as “London smog”, place where it is prevalent.

What causes smog?

Smog is formed when gases (for instance, ground-level ozone) and airborne particles react in the air with heat and sunlight.

Some of these pollution gases, called precursors, drive to ground-level ozone and particle formation, thanks to a sequence of photochemical reactions. Precursors gases are: volatile organic compounds (VOC), sulphur dioxide (SO2) and nitrogen oxides (NOx).

Apart from vehicles exhaust systems and its combustion of fossil fuels, smog-creation gases are also produced by coal fires and volcano eruptions.

However, smog usually appears in dense traffic situations and with optimal weather conditions to chemically react: high temperatures, calm winds and sunshine.

How smog affects the environment and humans health?

Since smog is composed by very tiny particles and gases, it can penetrate deeply into our bodies, specifically into the lungs of both animals and humans. A lot of species and green life are killed by smog due to the few adaptability to breathe purely in such toxic environments.

Smog exposure can drive to respiration problems such as breathing passages, decrease lungs working capacity, shortness of breath, pain when inhaling deeply, wheezing and coughing. Other respiratory issues or illnesses also related to smog are pneumonia, cold, chest pain, inflammation in lungs tissues or even premature death due to cancer or unknown respiratory diseases.

Eye and nose irritation are usual symptoms of smog exposure, drying out the protective throat and nose membranes and interfering with the body’s ability to fight infection and possible illness.

Furthermore, some studies have proven it also can drive to increase alzheimer probability, low birth weight or other birth risks. Hospital admissions and respiratory deaths often increase during periods when ozone levels are high. Moreover, smog can cause visibility problems for drivers and thus increase the danger of having a car accident.

Sensitive groups can suffer more intense symptoms and effects, this is why it is recommended for them to avoid any kind of exposure. This group at greater risks is formed by elderly, children and people with respiratory or heart problems, such as asthma, bronchitis or emphysema.

smog effects on children

Levels of unhealthy exposure

Ozone is the most risky air pollutant in smog. According to the U.S. Environmental Protection Agency (EPA) and its Air Quality Index, 8 hour average ozone concentrations can be classified as:

  • Unhealthy for sensitive groups: 85 to 104 ppbv
  • Unhealthy: 105 to 124 ppbv
  • Very unhealthy: 125 to 404 ppbv

On the other hand, smog can cause harmful effects to the vegetation and the environment as well, denying plant growth, damaging forests, crops and vegetables, such as soybeans, wheat, tomatoes, peanuts and cotton.

What you can do to prevent smog?

When smog appears, you can only protect yourself with a face mask or staying indoors. To avoid these situations you can embrace some practices in order to prevent smog formation:

  • Change your car habits:
    • Drive less to cut down emissions.
    • Maintain your car to make it work properly.
    • Fuel up in cooler temperatures.
    • Purchase a hybrid or electric vehicle.
  • Change your consumption habits:
    • Avoid high VOC products, not only for smog prevention but also to have a good air quality indoors.
    • Avoid gas-powered yard equipment.
    • Buy local to reduce transport emissions.
    • Be energy efficient in your home.
  • Taking a stand:
    • Don’t support organizations that have poor environmental practices.
    • Promote your stance and what are you doing to solve the problem with your closest family and friends and even in Social Media.
    • Contact local politicians and business leaders.

Areas affected by smog

Smog is not only taking place in particular places, it can be formed wherever pollutants are emitted and in other areas where pollution has been transported by wind flowing.

However, there are some cities or places where smog is usual and can become a real nightmare for inhabitants:

  • Canada
  • Delhi, India
  • Beijing, China
  • London and other areas in the United Kingdom
  • Mexico City, Mexico
  • Santiago, Chile
  • Tehran, Iran
  • Los Angeles and the San Joaquin Valley, United States
  • Ulaanbaatar, Mongolia
  • Southeast, Asia
  • Pakistan

The Great Smog of London 1952

london air pollution

Otherwise, the worst case of urban smog happened in London from Friday 5 to Tuesday 9 of December 1952. It was called the Great Smog of London (and the Great Smog of 1952 as well) and it caused more than 4.000 deaths and 100.000 illnesses during that period, most involving respiratory problems. Furthermore, recent studies have proven that over 6.000 people more passed away on the following months.

Among a lot of reasons, it was originated because of low temperatures during that winter, fact that made Londoners burn more coal to warm themselves. Later an anticyclone settled over a windless London, which caused a temperature inversion and favoured smog to be formed and persistent over the city.

What is a smog check?

Smog Check inspections are designed to identify vehicles with excess emissions. For instance, in California (United States), there is a Smog Check Program that has become very popular and it is an important part of the improvements made to control air pollution.

Despite other countries do not have smog tests or stations by themselves, “smog emissions” are checked every time your car gets its circulation license and inspection sheet.

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Air pollution effects: Haze Weather

What does haze weather mean?

Haze is an atmospheric phenomenon where visibility of the sky is reduced due to the high presence of smoke, dust and other airborne particles, giving the sky a bluish or brownish color. According to the World Meteorological Organization, horizontal obscurations can be classified among fog, ice fog, steam fog, mist, haze, smoke, volcanic ash, dust, sand or snow.

haze weather

Haze measurement

The coefficient of haze, which is also known as smoke shade, is a measurement of visibility interference in the atmosphere and it is calculated by the absorbance formula: COH = log10 (I1 / I0).

However, haze is usually measured using the Pollutant Standards Index (or PSI), which is a type of air quality index that indicates the level of pollutants in the air. It may differ depending on the country since other indices are used worldwide, such as Air Quality Health Index or Air Pollution Index. Some examples of countries using PSI as an indicator of air quality are the United States (until 1999, when it was changed for Air Quality Index) and Singapore.  

Singapore’s National Environmental Agency (NEA), indicate PSI with a number between 0 and 500. If air quality reaches levels over 100 PSI, population may notice it and can suffer health effects. As a point of interest, Singapore has the 3-hour PSI reading record with 401 (21st June 2013).

Causes and effects of haze

Haze particles emissions come from sources such as farming (ploughing in dry weather), traffic, industry, and wildfires. Cars combustion engines or industrial pollution emit sulfur dioxide particles (SO2) that generate haze, which after chemically reacting in the atmosphere with other compounds can become smog or acid rain.

Wind can carry haze from one country to another, like what happened in Malaysia in 2013. Despite Arctic has not enough emissions to pollute its own air, during springtime that region suffer a reddish-brown haze due to air pollution emissions mainly coming from Asia. The most characteristic feature of Arctic haze is the ability of its chemical ingredients to persist in the atmosphere for an extended period of time, in comparison with other pollutants.

In Indonesia it is typical to burn trash because of the lack of cleaning services, or plantations, in order to clean land during dry weather. Especially in the islands of Sumatra, Kalimantan and Riau, fires are more regular, what made these places main sources of haze.

fire indonesia haze

In 2013, due to indonesian forest fires, Kuala Lumpur (Malaysia’s capital) suffered extreme haze weather conditions. As Indonesia is considered the world’s third largest greenhouse gas emitter, in 2014 after what happened with Malaysia it also became part of ASEAN Agreement.

Other laws or agreements to preserve the environment and solve visibility problems are: the Interagency Monitoring of Protected Visual Environments (IMPROVE) program as a collaboration between US EPA and the National Park Service, or the Clean Air Act also implemented by US Environmental Protection Agency (EPA).

ASEAN Agreement

In order to reduce haze pollution in Southeast Asia, the Association of Southeast Asian Nations signed in 2002 an environmental agreement. In 2014 this agreement was ratified. Member states of the agreement are: Malaysia, Singapore, Brunei, Myanmar, Vietnam, Thailand, Laos, Cambodia, Philippines and Indonesia.

What is the difference between haze, fog and mist?

haze fog mist difference

The three of them imply reduced visibility because of weather conditions (for fog and mist) or air pollution (for haze). This is the main difference, while fog and mist are formed by the suspension of water droplets, haze is made of extremely small and dry airborne particles.

Fog is the name given to resulting visibility of less than 1 km, according to the international agreement for aviation purposes. However, in weather forecasts for the general public it is understood as less than 180 meters of visibility. On the other hand, mist is exactly the same phenomenon as fog lowing its density and increasing visibility to 1 km or more.

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Air pollution effects: Global Warming

What is global warming?

Global warming can be defined as an increase in the average temperature of the Earth due to air pollutants, which collect sunlight and radiation and produce the greenhouse effect. This pollution layer avoids the reflection of sun rays by Earth’s surface towards space, which raise the temperature in our planet among a lot more consequences.

sea level rising

It is a real problem since statistics and evidence are there. According to NASA’s data:

  • Carbon monoxide levels in the air are the highest in 650.000 years, concretely up to 408 ppm (parts per million).
  • 17 out of the 18 warmest years in history (which have been recorded) have taken place after 2001. Global temperature has increased 1°C (1,8°F) since 1880.
  • Arctic ice minimum levels have decreased 13,2% each decade. In 2012, Arctic summer sea ice shrank to the lowest extent on record.
  • Satellite data show that Earth’s polar ice sheets are losing mass at speed of 413 gigatonnes per year.
  • Sea level is currently increasing 3,2 millimeters per year.

Causes of global warming

The main cause of global warming, according to most climate scientists, is the greenhouse effect. Greenhouse gases absorb heat and re-emit it in all directions warming up the lower atmosphere and the Earth’s surface.

Burning of oil and fossil fuels, which mainly come from sources such as vehicles combustion engines and carbon industries, emit huge amounts of carbon molecules to the atmosphere, where they react with oxygen to create carbon dioxide (CO2). More sources of global warming contributing to create that pollution layer “in charge of microwaving the Earth” are soot and aerosols, among many others.

Which are the greenhouse gases?

These gases can be classified in two groups depending if they react to changes (physically or chemically) (“feedbacks”) or not (“forcing”). Greenhouse gases are:

  • Water Vapor (H2O): The most abundant greenhouse gas. It performs as feedback: the warmest the Earth is, more water vapor will be found in the atmosphere (clouds and precipitation).
  • Nitrous oxide (N2O): Human-made activities such as soil cultivation, use of fertilisers, fossil fuel combustion, nitric acid production or biomass burning.
  • Methane (CH4): An active, but limited greenhouse gas emitted by human and biological sources like agriculture or ruminant digestion associated to livestock.
  • Carbon dioxide (CO2): Although produced naturally by respiration or volcano eruptions, carbon dioxide emissions have become an environmental problem due to anthropogenic sources. Since Industrial Revolution, activities such as industrial operations, deforestation or burning of fossil fuels, among others have massively increased the emission of this greenhouse gas.  
  • Chlorofluorocarbons (CFCs): synthetic compounds produced by industrial activities and controlled by some governments due to its strong effects related to the ozone layer depletion.

global warming and climate change

Global warming environmental effects: Climate change

Mainly, global warming implies the worst of the air pollution environmental effects: Climate change! By warming up the surface of our planet, we get an impact almost worldwide.

Some of the current evidence of climate change are:

  • Ice declining and sea level rising:
    • Ice sheets slip: The warmer the planet is, faster the ice will thaw.
    • Glacial shrink, especially in places such as the Alps, Himalayas, Andes, Rockies, Alaska and Africa.
    • Less snow covering the top of mountains.
    • Sea level rise at current speed of 3,2 millimeters per year, which in 50 years mean coastline will have risen over 15 centimeters.
    • Downturning the thickness and extension of Arctic sea ice.
  • Extreme weather events:
    • Extreme events such as hurricane Katrina (2005), which hit New Orleans and other american cities of Louisiana and Florida. In this section plagues, more and stronger rains, intense heat waves, floods, and others are also included.  
  • Ecosystem changes:
    • Warmer global temperature: As already mentioned, since the 19th century the average temperature of the planet has increased by 1°C (1,8°F).
    • Warming oceans: oceans have collected this increased heat within the top 700 meters.
    • Ocean acidification:  The acidity of surface ocean waters has increased by about 30% due to humans activities emitting carbon dioxide into the atmosphere.

glaciar deflation

However, this does not end here. The effects will continue to grow and environmental impact will rise over the years:

  • Temperatures will continue increasing.
  • Extending frost-free and growing seasons for crops.
  • Precipitation patterns will be affected.
  • Changes in natural habitats that will cost the extinction of a huge amount of plants and animals.
  • More droughts and heat waves.
  • More intense and stronger hurricanes.
  • Sea level will rise from 30 to 120 centimeters by the end of 21th century.
  • Arctic won’t have ice anymore.

Health effects of global warming

Despite climate change has direct health effects in humans, most of the problems or issues it causes are due to environmental alterations. Heat waves, natural disasters, breathing poor air quality and spreading diseases are just some examples.

Some groups such as kids or elderly are more vulnerable to illness or death due to these global warming consequences. However, it affects differently depending on the region and the capacity of each country to adapt to changes.

Global warming will also affect crops, livestock, fisheries and others by reducing yields, seasonal and weather changes, the need of using more pests, etc. Furthermore, drinking water will become harder to find, less availability and of less quality.

How to stop and prevent global warming?

Changing your daily routines is not easy, but if you expect a future we need to make the effort and change some habits. It is not only a government’s duty, it is in our hands!

Some possible solutions to reduce global warming are:

  • Investing in renewable energies for our homes, businesses, means of transportation, etc.
  • Not use fossil fuel electricity anymore.
  • Change our food production habits in order to prevent deforestation and forest degradation, as these emissions represent the 30% of the world’s heat trapping emissions.
  • Improving in nuclear power, so it has fewer pollution emissions.
  • Improve and apply new low-carbon and zero-carbon technologies.
  • Reduce water waste.

Each of our individual inputs will make a change and guide the planet to a better future. If we expect our leaders and politicians to make everything, the situation is not going to change. For example, US President Donald Trump said that “global warming is a hoax” years before the elections. If the president of one of the top countries in the world is not taking care of our planet, we need to make the difference throw individual efforts.

On the other side, there are countries aware of the problem that created alliances and agreements about global climate change over the years, such as The Paris Agreement (the latest UNFCCC agreement).

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Natural causes of air pollution: Wind Erosion

Wind Erosion definition

People in many areas aren’t conscious that wind erosion is a serious environmental problem and one of the most important natural causes of air pollution. There are places where this phenomenon is most likely to cause problems, especially in flat and bare areas or dry and sandy soils. However, to a greater or lesser extent, we all suffer from the air pollution this event provokes.


What is wind erosion? It is a natural process that moves soil from one location to another by wind power, often causing significant economic, health and environmental impact. At this point you might have thought about extreme cases, where a strong wind lifts a large volume of soil particulate matter into the air to create dust storms. However, light wind rolls soil particles along the surface, and this is the most common type of wind erosion.

At the end, it is wind who causes erosion, but the external facts, such as landscape or land condition, are the ones that determine the severity and the impact of this phenomenon. The following is a list of wind erosion examples:

  • Rock formation
  • Dunes
  • Canyons
  • Sand and dust storms


After wind erosion, wind deposition occurs, and it is the geological process wherein soil particles or sediments are deposited and added to the mass of landforms.

Types of wind erosion

Suspension, Saltation and Surface Creep

There are 2 types to divide wind erosion, and one of them is through suspension, saltation and surface creep:

  • Suspension: it is when particles are lifted into the wind, and once in the atmosphere, these dust and dirt particles can be transported very high through long distances, creating harmful environments for those who breath them.  
  • Saltation: it is when particles are lifted into the air, but this time they are drift horizontally. When these strike the ground again the velocity determines if they rebound back into the air or knock other particles into the air.
  • Surface Creep: in this process, the particles are rolled across the surface because wind is not too strong or the particles are too heavy to be lifted.

wind erosion wall

Deflation and Abrasion

Deflation and abrasion are another way to categorize the types of wind erosion. Deflation occurs when wind moves particles that are loose and abrasion is when an area is eroded directly by airborne particles. In other words, deflation and abrasion indicate what agent is causing the erosion.

Causes of Wind Erosion

Wind erosion occurs when something causes a reduction to the ground cover below 50% or/and removes trees and scrub that act as windbreaks. Some example are land clearing, overgrazing by livestock or cropping.

However, as the name suggests, wind is the principal cause of erosion. It can happen anywhere and any time the wind blows and it is more strong where the soil or sand is not compacted or is of a finely granulated nature.

wind erosion

What can prevent wind erosion?

Wind erosion prevention is topic which governments globally should focus more, as it has a huge impact on land production. The loss of nutrients affects directly the ability of the soil to properly produce drops, and soil production is one of the main elements for human race to survive. The following facts are the five main ways to prevent or control wind erosion:

Surface/crop residues

The surface form and crop residues can help prevent wind erosion. If placed at the right angle, which is perpendicular to the existing wind, it protects the removal of soil particles and maintain the nutrients of the soil.

After the harvest, when the soil is highly exposed to wind erosion, it is recommended taking any harvest residues and spread them throw the soil, so these residues act as a protection layer for the soil particles and its nutrients.

Permanent vegetation cover

A permanent vegetation cover is not only for wind erosion protection, but also for the conservation of water and air resources. This vegetation cover includes growing grass, shrubs, trees, vegetables or legumes.

vegetation cover

Surface roughening

In large areas or areas where a permanent vegetation cover isn’t enough to protect the soil from wind erosion, three extra surface roughening methods come up: soil crusts, crosswind ridge, and clod-forming tillage.

Reshaping the land

Giving the land the ideal shape to protect it from wind erosion is key, specially on agricultural activities. It may not be available for everyone since it is a bit expensive in some cases, but it is a very effective way to lessen the potential for erosion.

shaping land


It is one of the best ways to lessen the erosion of soil since the wind force finds it difficult to carry the soil particles on a wet surface. However, too much water on a soil affects negatively the soil and its nutrients, and some very hot and dry areas cannot apply this technique.

Wind Erosion as an Air Pollution Source

Appart from the economic costs, airborne particulate matter and dust are harmful to humans when inhaled. It is highly recommended having a dust mask if you live in an area where dust storms are common.

Airborne dust is directly related to the probability of asthma and other health problems. You can refer to our blog post on health effects of air pollution to know everything about it.

inhalator for asthma

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Natural causes of air pollution: Volcanic Eruptions

Volcanic Eruption Definition

A volcano is an open fissure on the surface of the earth. Active volcanoes are those from which lava, volcanic ashes, rocks, dust and gas compounds escape on a regular basis (10.000 years are considered regular with volcanoes, so you can feel safe if you have one around) due to the phenomenon of volcanic eruptions.

volcanic eruption

In the world there are several active volcanoes which cause air pollution, danger to life forms and massive destruction of the land and the environment. Indonesia is the country with most active volcanoes in the world with 76 of them and total of 147 volcanoes.

Causes of Volcanic Eruptions

There are many causes that can lead to a volcanic emissions, many of them are still unknown by humans, which volcano eruptions very hard to predict. However, volcanologists have made some researchers to determine a few catalysts of them:

  • Movement of tectonic plates: whether it is because one is pushed under another one or two tectonic plates are moved away from each other, this creates a massive movement on the layers of planet earth (changing the structures of magma, sediments and seawater) and cause a volcano to erupt.
  • Decreasing temperatures: the volume of magma changes when it crystalizes, so it can push away liquid magma and create a volcanic eruption.
  • Decrease in external pressure: this fact provokes an increase in the internal pressure of the volcano and causes and eruption if it is not capable of holding back the lava.
  • Buoyancy of the magma: if the density of the magma between the zone of its generation and the surface is less than that of the surrounding and overlying rocks, the magma reaches the surface and erupts.
  • Pressure from the exsolved gases: andesitic and rhyolitic magma compositions contain dissolved volatiles (gases) such as water, sulfur dioxide and carbon dioxide. This gas bubbles are held by magma, but just like a carbonated drink, the bubbles of gas rise to the surface of the magma chamber creating a volcanic eruption.
  • Injection of a new batch of magma into an already filled magma chamber: this phenomenon causes some magma to move up and spill or even erupt at the surface.

magma eruption

Effects of Volcanic Eruptions

Volcanoes have huge impact on our society and environment when they erupt, here there are some of the many positive and negative effects of volcanic eruptions:

  • Negative effects: volcanic eruptions, which sometimes generate earthquakes, can destroy landscapes, natural resources, wildlife and human lives and their properties. This phenomenon can also discharge ashes very high into the atmosphere, having negative consequences on the ozone layer. Moreover, ash and mud can mix with rain and melting snow and create situations like lahars (also called mudflows) or acid rain. In other words, volcanic eruptions can destroy civilizations, like what happened to Pompeii.


  • Positive Effects: sometimes eruptions can leave an extraordinary beautiful and natural scenery, attacking tourists to the area. However, one of the most useful positive effects is that they often leave potential for geothermal energy, making life more easy for those around the area. Finally, some volcanic eruptions provide valuable nutrients for the soil, which are later used as fertile soils for agriculture.

volcanic landscape

Types of Volcanic Eruptions

Air Pollution of Volcanic Eruptions

Volcanic Eruptions release massive quantities of solid pollutants and gases, forming enormous clouds that can affect areas miles away from the volcanic eruption. Therefore, volcanoes are an international form of air pollution, but not just for us, as a lot of this greenhouse gases and aerosols go directly into the atmosphere.

Every volcanic eruption is different on impact, and therefore different on the quantity and a variety of pollutants emitted. On average the outgassed composition release is 79% water vapor (H2O), 11,6% carbon dioxide (CO2), 6,5% sulphur dioxide (SO2) and 2,9% of other pollutants.

However, the range of pollutants released on a volcanic eruption include: carbon dioxide (CO2), sulphur dioxide (SO2), hydrogen sulfide (H₂S), hydrogen (H₂), hydrogen fluoride (HF), hydrogen chloride (HCl), bromide oxide (BrO) and carbon monoxide (CO). Highly exposure to these gases has detrimental impact on living organisms both terrestrial and marine.

On the other side, particulates are another source of air pollution produced by volcanic eruptions. Mainly ashes and including all types of sizes, the ones that help forming toxic clouds are usually PM10, PM2.5, PM0.3 and thinner.

volcanic eruption

These pollution clouds can travel major distances, like crossing oceans, dangerously affecting people and environments who didn’t even notice the eruption. If you are facing a polluted cloud caused by a volcanic eruption, you may want to have a look at the following content on what to do and how to prevent these events.

What to do before, during and after a Volcanic Eruption

Before a Volcanic Eruption

There are several precautions you have to take into account before a volcanic eruption, and it is good to discuss them with your family members (including kids) before the event to prevent nerves and panic.

The first step is to have a household evacuation plan (that includes your pets). If you need guidance creating one you can find all you need to know and some templates here.

Secondly, as during the volcanic eruption you might lose electric supply, you need to have a flashlight, a battery radio and extra batteries for both. It is important to keep yourself up to date. We will write about it below, but during the previous days stay informed about the governmental media, community’s risk and response plans.

Thirdly, you will need health protection to ashfall and air pollution. To protect your eyes it is recommended having a pair of goggles, and to protect your respiratory system you should buy industrial protection face masks. Note that the majority of common pollution masks are not valid, you should have one approved for industrial and extreme purposes.

Finally, as any scenery is possible, you need to be prepared to live indoors for long periods without electricity power nor drinking water so buy food (if possible durable goods) and bottled water to survive you and your family members a few weeks. Make sure to have all the outdoor stuff and you want to keep safe inside, volcanic eruptions can damage any furniture, machinery or material.

During a Volcanic Eruption

If your outdoors you should quickly look for a shelter indoors. If it is not possible stay out of designated restricted zones, areas downwind of the volcano and river valleys downstream of the volcano. Take into account that even if you are miles away from the eruption you can experience harmful consequences.

In the case you get caught by an ashfall wear goggles (never contact lenses), a dust mask prepared for industrial and extreme purposes and a keep as much of your skin covered as possible.

protection equipment

On the other hand, if you are indoors you should be constantly listening to a local station on the battery radio for updated emergency information and instructions. It important because your area can be at any moment evacuated. During the indoor period, make sure to close all window, doors, and dampers to keep volcanic ash from entering.

In case of evacuation, strictly follow the instructions issued by local or national authorities and put your previously studied household evacuation plan. This rule is the most important one because even though it may look safer to stay home, take into account that your life must be in danger.

After a Volcanic Eruption

If you pass a volcanic eruption you will surely never forget it. There are some tips you should take into account to return to normality as soon as possible.

Firstly, you should not stop listening to local news for authorities updates, if you were evacuated, don’t return home until the authorities say to do so because it is safe. If people around you are injured, check the zone is safe for you and then call an ambulance and provide first aid (if you know something about it). Your family and friends might be worried as well, so tell everyone you are safe.

Secondly, even though the eruption has passed, if possible stay indoors and use the pollution mask (indoors and outdoors), because pollution particles (mainly ashes) will still be floating in the environment, and these can be extremely harmful. Moreover, keep animals away from ashes and wash them to prevent them from eating ashes.

Emotional recovery can be difficult because you may see some astonishing images and receive some terrible news. Here is a link to help you with this recovery.

If you have to return home try not to drive on heavy ashes roads because these are extremely harmful not just to humans health, but also to car engines. Never stop wearing any of the protective clothes, you cannot allow to expose yourself even for 30 seconds.

Once you get there, take pictures of the damages caused by the volcano for insurance purposes. The next step is to start cleaning your house from ashes and other volcanic materia, starting by the roof and gutters, which can cause your house to collapse. To help you with this task, read the following link for proper guidance.

Last Volcanic Eruption

Here comes an interesting fact about volcanic eruptions: any time there are several volcanoes on an eruption process. Volcanic activity is much more powerful and regular than we usually think. To know what volcanoes are erupting today, click the following link.

volcanic eruption

Largest Volcanic Eruption

World’s history has seen some supervolcano eruptions, often called big bangs on the earth, and science explains that these major catastrophes occurred before human life was born.

However, during humans history there has been some major eruptions as well, and since 1980 we have been measuring their impact throw the VEI (Volcanic Explosivity Index) indicator. VEI is measured just like earthquakes, on a scale from 1 to 8, and each number is ten times greater than the previous one.

In the last 10.000 years there haven’t been any VEI-8 volcanic eruptions, luckily for us, but on the following list we name some of the most recent major volcanic eruptions:

  • Tambora – April 10, 1815
  • Krakatoa – August 27, 1883
  • Santa María – October 25, 1902
  • Novarupta – June 6, 1912
  • Pinatubo – June 15, 1991
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Natural causes of air pollution: Forest Fire

What are Forest Fires?

Forest fire originated by natural causes, or in other words without human activity involved, are also known as bushfires or wildfires. These are given when fire has place in highly dense vegetation areas.

Furthermore, bushfires also contribute to deforestation, what indirectly affects air quality in forests and jungles, that are considered Earth’s lungs.

Australia is well known as a country with plenty of vegetation and wildlife. However, the country has an important issue with bushfires, as they cost more than £180 million each year (both natural and man-made).

forest fire

Unfortunately, there are a huge amount of notable bushfires in history. Some examples of most important wildfires worldwide have been:

  • China (1987) burning over 72.000km2 and Indonesia (1997) burning over 97.000km2.
  • Currently the U.S. and Canada have been the most active countries last 10 years with bushfires burning around 6.6 and 6.2 acres/year respectively.

A long time ago, palaeowildfires burnt plant material leading to fossil charcoal formation. Nowadays, fossil charcoal is being used as an indicator of palaeoclimatology in order to study evolution on bushfires over the years.

Causes of Bushfires

There are several different causes that lead to forest fire, but these are made more likely when the weather is hot and dry. Fallen leaves, dry grass or branches easily light up and can cause serious trouble to both urban and rural areas.


These terrible events often pass in just a few minutes, but they can last days, or in very unfortunate situations even months. The real threat when it comes to bushfires are high winds because these fan the flames and spread the blaze.

Forest Fire Pollution

Forest fire release pollutants like smoke, sulphur dioxide, nitrogen dioxide, ozone, particulate matter and carbon monoxide into the atmosphere. The bigger the bushfire, the bigger emissions.

In small amounts, carbon monoxide is present human bodies. The problem is that when inhaled in large amounts, and large amount of this gas are emitted on bushfires, it becomes toxic and can cause death.

Particulates on forest fire are either solid or liquid and consist of soot, tars, and other volatile organic substances. These particles can have different sizes: PM10, PM2.5, PM0.3 and smaller. They can cause cardiovascular and respiratory problems if they penetrate deeply into humans lungs.

Nitrogen oxides and sulphur dioxides are minor problems when it comes to forest fire. Nitrogen oxides are only released in big bushfires, as they only appear at greater temperatures than 1,500 degree centigrade. On the other hand, except when peat and muck soil are involved, sulphur dioxide only appears to be less than 0,2%.

Health effects of wildfires

Wildfire in California during this summer 2018 is causing hazardous air conditions across the state, prompting air quality alerts and forcing many residents to take refuge indoors to avoid unhealthy exposure to bad air.

It is not just about foggy and hazy skies, human’ risks and exposure are real. The air pollution from wildfires includes huge percentage of particles PM10, PM2.5, PM0.3 and thinner. Therefore, the health effects of wildfires are very similar to the ones explained during the blog post about Particulate Matter.

firemen wildfire

These health effects of forest fires include coughing, sore throats, extreme wheezing, cardiovascular illnesses and problems into lungs and bloodstream. Of course, sensible groups like children or elderly, are more likely to acquire these symptoms.

However, what do you have to do in the event of a forest fire? Firstly, you should be worried about the dangers of wildfires, so stay tuned to a local station for recommendations. Additionally, to protect yourself from air pollution: wear some kind of pollution mask, avoid staying outdoors and close all the opening from your house to prevent air pollution to enter. Finally, avoiding riding cars will help reduce SMOG, as this is produced with the mixing of combustion gases and the air pollution produced in forest fires.