Black Carbon – the Elephant in the Room!


Jim Mills, Managing Director, Air Monitors Air Monitors Limited, Unit 1 Bredon Court, Brockeridge Park, Twyning, Tewkesbury, Gloucestershire, GL20 6FF, UK Tel: +44 (0) 1684 857530 • Fax: +44 (0) 1242 292028 • Email: enquire@airmonitors.co.uk • Web: www.airmonitors.co.uk


Traditionally, ambient particulates have been measured gravimetrically according to their size. However, in this article Jim Mills, Managing Director of Air Monitors, will demonstrate that the


time has come to change or at least augment the way ambient particulates are monitored and regulated. Air Monitors has supplied most of the UK's ambient monitoring network, but Jim will explain why the measurement of Black Carbon could change the way we look at particulate pollution, so that focus will be given to strategies that could result in improvements to human health AND make a very significant contribution to the fight against climate change. Jim will also outline the rationale behind a new €3million EU funded project (Carbotraf) which will


use Black Carbon measurements to inform traffic management systems in both Glasgow and Graz. As a result of the health problems and mortality caused by smoke and soot in the 1950s, legislation was created in a number of countries including the UK and the US, which resulted in a significant decline in the levels of particulates. At that time, most of the particulate was derived from the burning of coal in homes and factories.


The most common measurement standards for particulates specify the mass of particulate that passes through a 10µm inlet (PM10) or a 2.5µm inlet (PM2.5). However, these methods take no account of the chemical or biological content of the particulate nor do they consider the number of particles.


Despite the dramatic reductions in PM10 and PM2.5 that have been achieved, a significant level of human health problems persist, including effects on respiratory and cardio vascular systems, including asthma, heart disease and cancer. People with existing lung or heart conditions may be more susceptible to the effects of air pollution.


Many scientists now believe that finer particles may be the major cause of ill health because they are able to travel deeper into the respiratory system, and because these tiny particles can act as sponges carrying small amounts of toxic species such as PAH’s and Dioxins which are adsorbed onto black carbon particles and transported deep into the body. PM10 and PM2.5 measurements provide a total figure for everything with mass in the sample and thereby assume that all particles are of equal significance. In reality this is not the case because some of the particles are benign from a human health perspective or are not anthropogenic so are of less interest from an air quality management perspective.


It is fortunate that the fine particles (from the combustion of fossil fuels) that are of most interest are black carbon and can be measured with an Aethalometer, which employs an optical method to only measure those fine particles which are black.


Importantly, an Aethalometer can provide a real-time readout of the mass concentration of 'Black' or 'Elemental' carbon aerosol particles in the air which means that live data can be used to manage the main contributor of urban black carbon: road traffic.


Global Warming


In addition to the public health issues relating to Black Carbon (BC), there is also a major consideration with regard to climate


change, because BC stays in the atmosphere for a relatively short period of time – from days to weeks, before falling to ground as a result of dry deposition or precipitation. This is an important consideration in global strategy to combat climate change because BC emissions are the second largest contribution to current global warming, after carbon dioxide


emissions. However, since CO2 stays in the atmosphere for many decades, emissions reductions will take a long time to have an effect, which means that efforts to reduce BC could have a much faster impact on global warming.


BC reduction is fast becoming recognised as a major opportunity in the fight against climate change. In June 2011, a UN Environment Programme (UNEP) study estimated that ‘near-term’ global warming could be quickly reduced by 0.5 degrees Celsius by a reduction in BC emissions and that this would have an even greater benefit in the Arctic where it could reduce warming by 0.7 degrees.


BC increases global warming by absorbing sunlight, darkening snow and influencing the formation of clouds. The effects of BC are most noticeable at the poles, on glaciers and in mountainous regions – all of which are exhibiting the greatest effects of climate change.


Why has the elephant been ignored?


In the 1950's it became clear that a dramatic reduction in airborne smoke and soot was required and the PM10 and PM2.5 monitoring standards provided useful tools with which to measure progress. In addition, other measures of air quality


such as SO2, NOx and Ozone were developed, but the significance of BC has only become clear more recently.


In 1952 over 4,000 Londoners (above the ‘normal’ mortality rate) are believed to have died as a result of the Great Smog.


IET November / December 2011 www.envirotech-online.com


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