Watch the icecaps melt away

I came across this animation via, a blog I subscribe to. It covers the period from the last glacial maximum 21,000 years ago and ends 1,000 years in the future., and shows the ice caps gradually melting away.

The visualsation has been developed at the Zurich University of Applied Sciences by Adrian Meyer and Karl Rege

“End summer sea ice is shown. The yellow line shows the actual shoreline. The future projection is based on the assumption of complete cessation of carbon dioxide emissions in 2100 (IPCC A2). Because world population is rather uncertain we froze to its current value.”


Particulate pollution – PM10 and PM2.5


Airborne particulate is a major component of urban air pollution. Anthropogenic sources  include combustion within car engines, solid-fuel combustion in households, industrial activities (such as building, mining, manufacturing of cement, ceramics and bricks, and smelting), quarrying and mining.

Epidemiological evidence indicates a clear relationship between exposure to particulate matter and effects on health, particularly smaller particles that can reach the deep regions of the lungs.

Table 1 – Health effects attributed to exposure to suspended particulate matter

Acute Effects Chronic Effects
Lung inflammatory reactions Increase in lower respiratory symptoms
Respiratory symptoms Reduction in lung function in children
Adverse effects on the cardiovascular system Increase in chronic obstructive pulmonary disease
Increase in hospital admissions Reduction in lung function in adults
Increase in mortality Reduction in life expectancy
Increase in medication usage

Source: Health aspects of air pollution: Results from the WHO project “Systematic review of health aspects of air pollution in Europe” (WHO, 2004)

With particulate matter, the size of the particles is very important, determining both how long particles remain airborne to be inhaled, and  whether they reach the deep regions of the lung where they can be absorbed.  Only particles smaller than about 10microns (one thousandth of a millimetre) will reach the alveoli.  Larger particles are deposited higher up in the respiratory system and removed on the mucocilliary escalator, but may then be swallowed and subsequently absorbed through the gastro-intestinal tract.

In practice, every individual will inhale a different fraction of a given dust cloud, and this can also vary depending on the particular environment and activity undertaken during exposure. However it is useful to define size selection criteria to use when sampling for airborne particulates, and this task has been undertaken by the International Standards Organisation in ISO 7708:1995 “Air quality — Particle size fraction definitions for health-related sampling”

Inhalable” particulate is the fraction of airborne material which enters the nose and mouth during breathing. Having entered the respiratory system the particles can potentially be deposited anywhere within the respiratory tract. However only very small particles can penetrate deep into the lung . The “thoracic fraction”, describes the mass fraction of particles penetrating beyond the larynx and the fraction of  particles reaching the deep lung  is referred to as “respirable fraction”.

When sampling for environmental pollutants, two other fractions are used – PM10 and PM2.5.

A picture of a human hair compared to the relative sizes of PM 10 and PM 2.5 particles

Carry out a search on the Internet for “PM10” and you’ll find a large number of sites that mention and define the term. For example:


“The notation PM10 is used to describe particles of 10 micrometers or less and PM2.5 represents particles less than 2.5 micrometers in aerodynamic diameter.”

Environment Agency

“PM10 is the term used to describe tiny particles in the air, made up of a complex mixture of soot, organic and inorganic materials having a particle size less than or equal to 10 microns diameter (10 microns is equal to one hundredth part of a millimetre).”

Health Protection Agency

“PM10 stands for Particulate Matter of less than 10 millionths of a metre (10 micrometers or 10 um) in diameter.”

Unfortunately (and disappointingly), all these definitions are incorrect.  PM10 and PM2.5 are defined by the International Standards Organisation as follows

PM10 – particles which pass through a size-selective inlet with a 50 % efficiency cut-off at 10 μm aerodynamic diameter.  PM10 corresponds to the “thoracic convention” as defined in ISO 7708:1995, Clause 6.

PM2.5 – particles which pass through a size-selective inlet with a 50 % efficiency cut-off at 2,5 μm aerodynamic diameter.  PM2,5 corresponds to the “high-risk respirable convention” as defined in ISO 7708:1995, 7.1.

So, in fact, PM10 is a standard size fraction where the median diameter is 10 microns. This means that 50% a significant proportion of the particles in this fraction have diameters greater than 10 microns. Similarly with PM2.5, 50% of the particles have a diameter greater than 2.5 microns.

I accept that trying to get the concept of particle size fractions across to the general public is not easy, and it’s often necessary to resort to simplifications. However, I think its inexcusable for the same erroneous definitions to be used in scientific publications and presentations and on websites aimed at environmental scientists and professionals.

Picture credits:

California Environmental Protection Agency

Climate change increases the impact of Persistent Organic Pollutants


Human activity releases a large number of chemical pollutants into the environment, many of which are harmful to human health. Some chemicals that are particularly noted for their ability to persist in the environment once released and for their harmful effects on health and the environment, are collectively known as “persistent organic pollutants” (POPs). These include many pesticides, dioxins, polychlorinated biphenyls (PCBs), furans, polycyclic aromatic hydrocarbons (PAHs), brominated flame-retardants, and organometallic compounds. Their chemical properties which often include chemical stability, low volatility, low water solubility and high lipid solubility, mean that once released they don’t break down in the environment but accumulate in soil and water and pass into the food chain. Bio-accumulation can then occur where they build up in the fatty tissues of animals, the concentration in the tissues increasing up the chain.

The effects on human health caused by POPs vary according to the compound, but potential concerns include cardiovascular disease, disruption of the endocrine, reproductive, and immune systems and neurobehavioral disorders, and some are confirmed or suspected carcinogens.

UNEP issued a press release on 7 December 2010 about the findings of a major international study on how climate change increases the planet’s vulnerability to persistent organic pollutants (POPs). The study, “Climate Change and POPs Inter-Linkages”is the first systematic and authoritative review of the impact of climate change on the release of POPs into the environment, their long range transport and environmental fate, and human and environmental exposure.

Katarína Magulová, Programme Officer of the Secretariat of the Stockholm Convention is quoted in the press release saying

“Climate change increases the planet’s vulnerability to persistent organic pollutants, by increasing emissions and the bio-availability of POPs, and thus the potential for bio-magnification through the food chain, one of the chief pathways of human exposure to POPs,”

According to the study, global warming contributes to a higher frequency of extreme weather events, which can cause severe flooding, triggering the secondary emissions of POPs. The higher temperatures resulting from climate change can also make wildlife more sensitive to exposure of certain pollutants.

An international treaty on POPs, the Stockholm Convention on Persistent Organic Pollutants, was adopted in 2001 and entered into force in 2004. The treaty, which is administered by The United Nations Environment Programme (UNEP),  requires Parties to take measures to eliminate or reduce the release of POPs into the environment.  Further details will be available when the findings are presented to the 5th meeting of the Parties to the Stockholm Convention in April 2011.

These findings illustrate the complexity of what happens when pollutants are released to the environment.  Some can cause short term effects on humans – for example irritation due to inhalation of gaseous pollutants such as sulphur dioxide – while other pollutants, such as POPs, exert their effects over a longer timescale.  In both cases the pollutants cause direct effects on health. However pollutants can also cause indirect effects. A particularly important example is provided by carbon dioxide. This is a major pollutant, but at atmospheric concentrations does not cause any direct effects on health. However, as the main “greenhouse gas” contributing to climate change it is indirectly responsible for a wide range of adverse health effects. There’s a good summary of the impacts on health on the WHO website. The findings from the study provides another example to add to the list.

Photo credit: Stock:xchng

Watch the glaciers retreat

Despite all the evidence that has been accumulating over the past few decades, there are still plenty of people who don’t accept that the climate is changing due to releases of “greenhouse gases” from human activities.

Anybody who has any doubts should watch this video of a talk by the photographer James Balog to the TED Global conference in Oxford earlier this year.

See also the extreme ice survey website

Pollution and human health

For a number of years now, in November / December I’ve contributed to an MSc in Pollution and Environmental Control, delivering a couple of lectures covering “Pollution and human health”.

People can be exposed to pollutants by inhalation of air pollution, and ingestion of polluted water or foodstuffs. Their effects on human health can be

  • Direct – where the pollutant causes direct harm to the individuals exposed
  • Indirect – where the effects of the pollutant on the environment and the resulting changes, can affect human health. Climate change, caused by the accumulation of carbon dioxide in the atmosphere due to human activity, can lead to health effects due to the increase in temperature (increased temperatures can lead to increased mortality in vulnerable groups, such as the elderly) and associated environmental impacts (drought, sea level rise etc.)

According to the World Health Organisation, an estimated 24% of the global disease burden and 23% of all deaths can be attributed to environmental factors. They estimate that in 2004  these resulted in a total of 5,309,000 deaths, the overwhelming majority from low income countries. (World Health Organisation 2006). However, richer countries are also affected, particularly by air pollution.

I’ve uploaded my presentation to Slideshare, and they can also be viewed below.