Notes on the First Workshop of the UK Dust Network
Health Consequences of Exposure to Natural Mineral Particles
AIM
To discuss recent work ideas on the health impacts of natural mineral particles (NMPs) and to identify
emergent themes and ideas for future multidisciplinary research proposals. These ideas will be presented
to the wider group for rejection or development in our main meeting in September.
These notes reflect the conversation and, to an extent, the presentations given, but all presentations will be
downloadable from the website.
ATTENDEES
Claire Horwell, Institute of Hazard and Risk Research, Uni. of Durham
– mineralogical and geochemical assessment of the health hazard of natural dusts. Director of the
International Volcanic Health Hazard Network and PI.
Peter Baxter – Institute of Public Health, Uni. of Cambridge
- occupational physician, medical expert on volcanic health hazards, sits on UK air quality standards
panels.
Clive Oppenheimer – Dept. of Geography, Uni. of Cambridge
- volcanology and application of remote sensing techniques for measurement of volcanic emissions.
Transformations of gases and aerosols in volcanic plumes.
Ed Derbyshire, Royal Holloway, London
– expertise in NMPs from China, Far East and Africa
Rod Jones, Dept. of Chemistry, Uni. of Cambridge
– measurements of gas phase and particulate phase in atmosphere using models. Health impacts are a
strategic interest.
Ken Donaldson – The Queen's Medical Research Institute, Uni. of Edinburgh
- Toxicologist with expertise in particles, silica, glass, asbestos, coal and nanoparticles.
Pierre Delmelle – Environment Department, Uni. of York
- environmental impacts of volcanic emissions. Gas/ash interaction in plumes, particularly looking at
surface chemistry.
Welcome and Introduction – Peter Baxter
Plan for UK Dust Network meetings:
 Meeting 1 - Core experts – provide conceptual framework for meeting 2.
 Meeting 2 – All experts – develop new concepts on risk and physico-chemical properties of
NMPs (natural mineral particles).
 Meeting 3 – Core experts – prepare final synthesis and report on interdisciplinary research needs
and opportunities including rapid response team for pollution incidents.
Themes:
 Exposure to NMPs through indoor and outdoor air pollution.
 Volcanic ash particles may be used in discussions as a model for toxicity studies and risk
assessment as much work has been carried out already.
 We are also interested in atmospheric dispersion and transformation of particles within the
atmosphere and/or a plume (chemical or physical transformations/interactions).
Key areas of focus:
 Characterisation of physical-chemical properties of NMP, their life cycles and transformation.
 Toxicology
 Exposure assessment
 Epidemiology and clinical research
 Policy making and public risk perception
Some issues:
 Seasonal dust storms affect millions of people
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15% of COPD cases are from occupational exposure to dusts (HSE)
Developing countries, using biomass for indoor fuel kills 1.6 million people each year (WHO)
Nature May 2007. Useful links:
http://www.nature.com/nature/journal/v447/n7142/pdf/447236a.pdf
http://www.who.int/indoorair/en/
http://www.thelancet.com/journals/lanonc/section?issue=12&section=Policy+Watch&volume=7
http://www.who.int/indoorair/publications/indoor_air_national_burden_estimate_revised.pdf
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Coarse particles 20-50% urban background PM10. Can’t discount the coarse fraction as cause of
acute diseases such as asthma and bronchitis.
Committee on Medical effects of air pollutants
Brunekreef and Forsberg 2005 – review on coarse PM and health.
http://www.ersj.org.uk/cgi/reprint/26/2/309
Crystalline silica linked to silicosis, lung cancer, COPD - HSE about to reduce work exposure
limit
Lung development in children – we don’t know if they are more susceptible to respiratory disease
than adults.
Definition of NMP- do we include biomass burning? Yes – soot is a big killer and there may be a
combined effect with other minerals.
Ed Derbyshire - Natural dust generation, transport, and properties, dominated by silicates.
 Dust is not generated in a standard desert environment, as is commonly thought. Glaciers deliver
material into un-vegetated terrain. Dust storms generated from lowlands. Deposition in lakes
which are then exposed and progressively stripped by storms. Seen in Tibet, Egypt and Mongolia.
Desert lung- Sahara – silicosis – higher in female population.
 Ladakh – no industry – but rich in dust storms. Cases of fibrosis in village at low altitude. Dust is
high in silica and has small grain size. Correlation of dust storm frequency and pneumoconiosis
incidence in Ladakh. Review of Ladakh papers: Norboo, T., H. N. Saiyed, et al. (2004). "Mini
review of high altitude health problems in Ladakh." Biomedicine and Pharmacotherapy 58: 220225. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VKN-4BYWSGP1&_user=121711&_coverDate=05%2F31%2F2004&_rdoc=3&_fmt=summary&_orig=browse&
_srch=docinfo(%23toc%236127%232004%23999419995%23504352%23FLA%23display%23Volume)&_
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ion=0&_userid=121711&md5=49d170d7cc703da0ba8449ca1384e976
 Case study – China – Hexi corridor – high incidence of lung disease in population but no
difference in gender. Camels have silicosis too. Only 3 studies on China – very high dust
concentrations. It was thought that desert dust is coarse but, in fact, fines present too.
 Lanzarote dust has had quantitative mineralogy on it (Johann Engelbrecht).
 Discussion on role of kaolinite and other clays in the presence of crystalline silica.
 Difficult to get hold of long-run dust filter samples for analysis. Long term global dust storm
frequency – mainly lake basins. Sources in all continents except Europe and Antarctica. Can look
at frequency of dust days (< 1 km visibility) around the world. Circulation of dust storms –
relevance to weather circulation patterns -NERC/Met Office observational campaigns of
chemical and atmospheric measurements of dust storms.
 Tanaka et al 2005. Biogenic silica also common in natural atmospheric dusts with impurities.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VH3-4GGXP7R2&_user=121711&_coverDate=07%2F31%2F2005&_rdoc=13&_fmt=summary&_orig=browse
&_srch=docinfo(%23toc%236055%232005%23999609978%23600128%23FLA%23display%23Volume)&_
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ion=0&_userid=121711&md5=eae62436596a904d44c427f6ecc44055
Claire Horwell - Cutting edge techniques for the analysis of volcanic ash and other natural particles.
 Objectives: To use mineralogy and geochemistry to make rapid assessments of the potential
health hazard of volcanic ash (and other natural dusts). To understand WHY a mineral or dust
may trigger a pathogenic respiratory response.
 Questions to answer: Is the dust small enough to enter the lungs? What is the composition of the
dust? Is the surface of the dust reactive? Are individual particles ‘pure’?
 Grain size: Is the dust small enough to enter the lungs? Several techniques ranging from state of
the art laser diffraction to basic sieving. Developed technique to predict the respirable fraction
from <63 m sieve data (Horwell 2007, accepted for publication in Journal of Environmental
Monitoring).
 Composition: natural dusts are often composed of 10s of different minerals, some of which may
be toxic. Techniques: SEM-EDX, XRD-PSD, Raman-SEM (state-of-the-art, allowing
identification of silica polymorphs in individual crystals).
 Reactivity of surfaces: Radicals formed by breaking bonds during fragmentation of rock. Radicals
are highly reactive, damaging DNA, proteins, lipids etc. and are likely to be one of several
triggering mechanisms for chronic lung disease. Volcanic crystalline silica doesn’t seem reactive
but Fe2+ can generate the hydroxyl radical when in contact with H2O2. I have found that basaltic
ash (no crystalline silica but iron rich) is even more reactive than andesitic ash but previously had
not been considered a health hazard. (Horwell et al. in review, EPSL).
 Evidence mounting that volcanic silica may not be toxic. Why is this? Silica may be impure –
coated with more inert minerals, intergrown with other minerals or open crystalline structure
allows substitution of silica for other cations during crystal growth. Recent work shows that
volcanic cristobalite is definitely impure with 1-1.5 % Al2O3 – Al known to ameliorate toxicity in
some circumstances. Use Raman-SEM, electron microprobe and TEM-EDX for this work.
 What next?
o Could alpha and beta forms of cristobalite and quartz have different toxicities?
o Extremely unusual to preserve beta variety but impurities potentially make it possible.
o Integration of work with toxicology.
o Application of techniques to other natural dusts e.g. coal and desert.
Peter Baxter - Health effects of volcanic ash.
 Gave summary of Mt St Helens eruption (May 1980) – ash aggravates chronic lung conditions.
 Gave summary of Horwell & Baxter 2006: Overview of respiratory health hazards of
volcanic ash :
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http://www.springerlink.com/content/f6144r17p4r30546/?p=909e3f62cbea4abfa278338cd85ac25
1&pi=0
Montserrat: Forbes et al. 2003: Asthma in school children on Montserrat – clinically and
anecdotally, there is a strong effect – many have left. Repeating study this year. Unknown if
children more susceptible to disease than adults.
http://oem.bmj.com/cgi/content/abstract/60/3/207?maxtoshow=&HITS=10&hits=10&RESULTF
ORMAT=&author1=Forbes&fulltext=Montserrat&andorexactfulltext=and&searchid=1&FIRSTI
NDEX=0&sortspec=relevance&resourcetype=HWCIT
Summary of Montserrat health studies. Summary of ash risk assessment modelling on
Montserrat.
Acid affect on vegetation.
Podoconiosis – non-philarial elephantiasis. Lava weathered to kaolinite – find kaolin
inflammatory reaction in lymph nodes – blocks lymphatic system so legs swell up.
Ken Donaldson - Particle toxicology
 What makes some particles harmful and some less harmful?
 What makes some people vulnerable and others not?
 What is the mechanism of disease – can we stop its progression?
 All particle exposures are mixed – what is the harmful dose?
 Cardiovascular disease – largest cause of death from air pollution.
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Summary of deposition of particles in the lung. Big doses of particles around terminal
bronchioles because low air movement. Particle has to pass through mucus layer in order to reach
cells. Particles deposit in alveolar duct bifurcation. Alveoli are much bigger than respirable
particles and macrophages are around 20 m diameter. A harmful particle switches on genes that
cause inflammation. Inflammation often studied instead of disease itself because it is a stepping
stone – central to particle induced disease. Amount of surface area is important in driving
inflammation. So is reactivity.
Duffin, Tran, Brown, Stone, Donaldson, Pro inflammogenic effects of nanoparticles in vivo and
in vitro: highlighting the role of particle surface area and surface reactivity. Inhal Tox, in press.
Surface area x surface reactivity gives a measure of ability to cause inflammation.
Hawks Nest Tunnel Disster W Virginia 1930-32. 700 died and half out of 3000 ill – pure silica
sandstone. Gauley Mountain.
Changing quartz surface can change ability to cause inflammation – Duffin, Gilmour, Schins,
Clouter, Guy, Brown , MacNee, Borm, Donaldson and Stone (2001) Aluminium lactate treatment
of dq12 qtz inhibits its ability to cause inflammation.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WXH-45BBYF91W&_user=121711&_coverDate=10%2F01%2F2001&_rdoc=2&_fmt=summary&_orig=browse
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New themes in the field of particle toxicology:
o nanoparticles – get into blood and brain.
o Cardiovascular disease from Pm10
o Biomass burning indoors
o Fibres - making a come back because of nanotubes
Clive Oppenheimer – volcanology
 Frequency magnitude relationship of volcanic eruptions, overview of eruption types.
 Cocktail effect of aerosol, particles and gas.
 Pierre Delmelle (also present at meeting) uses XPS to look at surface composition of explosive
ash compared with bulk composition. Also used AFM to look at coatings of F on the surface of
the ash. Ken Donaldson says that acids and sulphates are low toxicity in the lung because lung is
so well buffered.
Discussion
 Middle eastern dust – little literature regarding its toxicity but thought to be less than Gobi.
 OEM editorial – oxidative potential be used as a metric for PM.
http://oem.bmj.com/cgi/content/extract/64/2/73?maxtoshow=&HITS=10&hits=10&RESULTFO
RMAT=&fulltext=oxidative+stress+PM10&andorexactfulltext=and&searchid=1&FIRSTINDEX
=10&sortspec=relevance&resourcetype=HWCIT
 We (Ken Donaldson) can now carry out inexpensive cell tests to look at inflammation to try and
confirm the ideas we have from the mineralogical analysis. Oxidative stress potential can be
measured by EPR (cell free)
 Differences in toxicity ash collected close to volcano and far away – atmospheric transport issues.
 It would be good to have a panel of particles of different toxicities and characterise every
mineralogical/geological aspect.
 Coarse (2.5-10 m) & ultra-fine particles (<1 m?) haven’t really been looked at. Until now
people have concentrated on the ‘respirable’ fraction (< 4 m).
 Number of people exposed is also crucial and duration of exposure.
 Per Schwarz, Oslo, toxicity of other dusts other than quartz in Norwegian road dust
 Silica in different situations as a proposal for future research
 San Cristobal ash – hydrothermally altered and high surface area.