Presentation on theme: "The toxicology of NMP (What adverse effects might we expect from exposure to NMP) Professor Ken Donaldson ELEGI Colt Laboratory."— Presentation transcript:
The toxicology of NMP (What adverse effects might we expect from exposure to NMP) Professor Ken Donaldson ELEGI Colt Laboratory Centre for Inflammation Research, Edinburgh University, Medical School, Edinburgh, Scotland
SiteSettingDiseaseExemplar particles AirwaysOcc/EnvBronchitisCoalmine dust, organic dust, PM10 OccSmall airways diseaseCoalmine dust, quartz OccSensitisation/asthmaMetals, organic dusts Occ/EnvLung cancerQuartz, metals, asbestos, PM10 Env Exacerbations of airways disease – COPD and asthma PM 2.5 ParenchymaOccEmphysemaCoalmine dust, quartz Occ Silicosis (pneumoconiosis)- nodular fibrosis Quartz, coalmine dust Occ Asbestosis (pneumoconiosis)- interstitial fibrosis Fibres Occ Progressive massive fibrosis Silicosis (pneumoconiosis)- nodular fibrosis coalmine dust Pleura, peritoneumOccMesotheliomaFibres Cardiovascular systemEnvAtherothrombosisPM 2.5 What diseases do particle cause or worsen? Parenchyma – pink alveoli Airways – white bronchial tubes Pleura – outside surface lung surface and chest wall surface Cardiovascular system – blood vessels and heart
Typical particles - Silica, asbestos, welding fume, nuisance dusts Exposure – High (mg/m 3 analogous to workplace) –peaks during shifts, zero at other times Exposed population - Predominantly healthy males <65 years old – no susceptibles due to healthy worker effect Typical responses - Pneumoconiosis, COPD, cancer, asthma If NMP have effects based on the occupational paradigm?
If NMP had effects based on the environmental (PM 10 ) paradigm? Exposure to - urban PM 10 containing combustion-derived nanoparticles Exposed population - Everyone but acute effects are only seen in susceptible and aged, ill populations with pre-existing oxidative stress and inflammation = susceptibility Exposure - Low (tens of ug/m3 as per urban environment) constant with peaks Typical responses – In susceptible populations - Exacerbations of COPD/asthma, exacerbations of cardiovascular disease, cancer In normals – very little except likely contribution to chronic disease
Factors contributing to toxic response to particles in the lungs Intrinsic toxicity of the material i.e. hazard Exposure concentration Length of exposure Contribute to dose Variable but low for NMP?? For NMP could be chronic or brief Generally low for NMP but exceptions e.g. quartz, metals
General scheme for what happens when harmful particles deposit in the lungs That fraction of the total dose that actually delivers toxicity
Current metricBiologically effective dose Particle Nuisance dust standard of respirable mass Surface area Carbon black (NP) Respirable massArea of reactive (unblocked or unpassivated) surface Quartz Fibres longer then 5 m, >3 m diameter and Aspect Ratio>3 Biopersistent fibres longer than ~ 20 m Asbestos Respirable massSoluble transition metals Welding fume (NP) Contained in PM 10 Organics/metals/surfaces Diesel soot Mass by PM 10 conventionOrganics/metals/surfaces PM 10 We are not good at measuring the BED in our metrics
The central hypothetical role of inflammation in the occupational paradigm Inflammation Occupational particles COPD, Airways inflammation Pneumoconiosis, Stimulation of fibroblast growth and ECM secretion Cancer Oxidative adducts of DNA Asthma Airways inflammation/ adjuvant effect
Inflammation PM 10 Superimposed on Airways inflammation of Asthma, COPD Exacerbation Hospitalisation Death (COPD) Increased inflammatory activity in plaques Atheromatous plaque formation is an inflammatory process Plaque rupture Myocardial infarction thrombosis Mortality The central hypothetical role of inflammation in the environmental paradigm Endothelial dysfunction Pro-thrombotic state
The ubiquitous role of oxidative stress in particle effects
Toxicology testing approaches Approach depends on aim - screening, mechanisms, regulatory NMP studies will be screening and mechanisms 1)Characterising the physico-chemistry – surface area, size etc, metals – aiming towards a structure:activity paradigm? 2)In vitro cell-free – e,g detecting free radical –generation, complement activation etc 3)In vitro cells – huge number of endpoints but should be pathophysiologically-relevant i.e. tells us about something we already understand as having a role in disease e.g. ability to cause a pro- inflammatory effect 4)In vivo- particle are instilled into or inhaled by rodents - lungs are then examined for effects (huge number of potential endpoints)
Example of an inhalation study with a NMP – Montserrat ash The importance of using controls to contextualise the response Rats inhaled ash along with a control dust TiO2 that is low in toxicity – at the same mass burden the ash was more inflammogenic as shown by more PMN in the lavage However, when plotted alongside particles of known toxicity, the ash was less than coalmine dust and quartz (see vertical axes).
Summing up- toxicology of NMP Particle toxicology is a mature science- we know what to do …but… Does NMP as a grouping make sense? Coalmine dust, quartz and asbestos are NMP but they are looked on as occupational diseases Do we have a disease from environmental exposures to NMP? How many people are at risk – in UK?, in Europe? In the world? What is the documented burden of ill-health due to environmental exposures to NMP? Only if there is a recognition that environmental exposures to NMP constitute a substantial health risk will funding be diverted from other known substantial heath risks …….Discuss