View
225
Download
4
Category
Tags:
Preview:
Citation preview
ASBESTOSASBESTOS
Francine Lortie-Monette, MD, MSc, CSPQ, MBA
Department of Epidemiology and Biostatistics
University of Western Ontario
2003
AsbestosisAsbestosis
Asbestosis is a model for other dust diseases as well as other forms of pulmonary fibrosis
Some dust diseases take years for clinical symptoms to develop
Dust DiseasesDust Diseases
Following removal from exposure, coal pneumoconioses may stop progressing but
Silicosis and asbestosis often do progress
AsbestosisAsbestosis
Model for:– Restrictive ventilatory impairment (vs
obstructive)– Interstitial lung disease
Why Study Asbestosis?Why Study Asbestosis?
Exposure has continued in European construction industry till the mid-1970s
What about developing countries?
Why Study Asbestosis?Why Study Asbestosis?
The resulting epidemic of mesothelioma in building workers born after 1940 did not become apparent until the 1990s owing to the long latency of the disease
Incidence rates are still rising
ASBESTOSASBESTOS
A broad term for a group of naturally occurring fibrous mineral silicates of magnesium and iron.
Asbestos-containing rock is mined, crushed and milled to obtain fibrous material, processed further into finer fibers.
ASBESTOSASBESTOS
Asbestos fibers are categorized into 2 groups:
Amphiboles Serpentines
ASBESTOS: ASBESTOS: Amphiboles (straight fibers)Amphiboles (straight fibers)
Those used commercially include:Amosite (brown)AnthophyliteCrocidolite (blue)
Others (e.g. tremolite and actinolite) are frequent contaminants of other silicates, including some vermiculites and talcs.
ASBESTOS: ASBESTOS: SerpentinesSerpentines
Used commercially:Chrysotile (3MgO-2SiO2-2H2O)
(the most common)
The Characteristics of ASBESTOSThe Characteristics of ASBESTOS
Natural resistance to heat and acid Tensile strength Remarkable thermal, electrical and sound
insulating properties
Have resulted in thousands of commercial applications, including floor tiles, boiler and pipe insulation, roofing materials, brake linings, and cement pipes.
Routes of ExposureRoutes of Exposure
Some ingestion (e.g. contaminated water)
Mostly inhalation:Aerosols generated by mining, milling,
product-manufacture, end use of product, and disturbance of asbestos-containing materials (e.g. renovations)
PathogenesisPathogenesis
Fibers provoke the accumulation of macrophages in alveolar ducts and peribronchial regions, which become thickened.
This fibrotic process progresses, leading to a stiffened, smaller lung with diminished capacity for gas exchange.
Progression can occur after exposure has ceased, due to the retention of fibers in the lung and persistent inflammatory response.
EffectsEffects
Pulmonary Fibrosis Pleural Thickening Pleural Effusion Cancer
Pulmonary FibrosisPulmonary Fibrosis
Results in restrictive lung disease that generally becomes manifest clinically 15-20 years after the onset of exposure.
Pulmonary Fibrosis (Cont’d)Pulmonary Fibrosis (Cont’d)
Most Prominent Symptom: Insidious onset of dyspnea on exertion
Signs: End-inspiratory basilar rales which persist after cough Decreased forced vital capacity (FVC), total lung
capacity (TLC) and diffusing capacity (DLCO)
Eventually, extensive fibrosis obstructs the blood flow throughout the pulmonary bed, causing pulmonary hypertension and compensatory right ventricular hypertrophy.
May occur within the first 10 years of exposure, and may be the first manifestation of illness.
Diagnosis by exclusion, i.e.: negative cultures of pleural fluid and pathological examination showing no malignant cells.
Patients may be asymptomatic; spontaneous resorption may occur within several weeks.
Benign Pleural EffusionBenign Pleural Effusion
Pleural Thickening Pleural Thickening (localized or diffuse)(localized or diffuse)
The most common consequence of occupational exposure to asbestos.
Latency: 20, and up to 40 years.
Associated with reduced FVC
Latency of 20 years.
Same cell types and histological features as other primary lung cancers.
Lung CancerLung Cancer
Considered a “signal neoplasm” because of its rarity in the absence of exposure to asbestos.
Latency: 20 years
Presenting symptoms often are chest pain and dyspnea, due to pleural effusions.
At high concentrations: cancer of the gastrointestinal tract, kidney, pancreas and larynx (also post ingestion).
Malignant Mesothelioma Malignant Mesothelioma of the pleura and peritoneumof the pleura and peritoneum
AsbestosAsbestos
Summary of a typical case:– Severe restrictive pulmonary impairment with
progressive dyspnea on exertion– No response to steroids– Deteriorates without ongoing exposure;
hypoxemia develops– Severe exercise limitation, with arterial
desaturation– Ultimately terminal respiratory failure
SilicosisSilicosis
Silica: hard crystalling mineral, silicon dioxide (SiO2), known as quartz
Commonly found in most igneous rocks and most types of sand
SilicosisSilicosis
Persons at risk:– Hard rock miners (gold, iron, uranium)– Smelter workers– Sand-blasters
SilicosisSilicosis
Most silicosis results from chronic exposure over years
Acute silicosis can occur from high exposure (sand-blasters), and can cause death from massive pulmonary fibrosis.
Silicosis: Silicosis: recommended readingrecommended readingFinkelstein MM: Silica, silicosis, and
lung cancers: a risk assessment. – Am J Ind Med 2000; 38: 8-18
– Copies will be available at LRC on February 10, 2003
Recommended