human health effects of particulate matter (pm) nathan pechacek, m.s. toxicology section texas...

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  • Human Health Effects of Particulate Matter (PM) Nathan Pechacek, M.S. Toxicology Section Texas Commission on Environmental Quality 512-239-1336 [email protected]
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  • PM 10 ~100 ug/m 3 PM 2.5 ~20 ug/m 3
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  • PM 10 ~400-1000 ug/m 3, PM 2.5 ~60-140 ug/m 3
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  • Presentation Outline Background information Health effects Challenges of epidemiological studies Sensitive populations Research needs Summary
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  • Background Information on PM and the Respiratory System
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  • Particulate Matter Complex substance: Sources Composition Size Travel distance Time spent airborne
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  • -reference: Brook, et al. 2004
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  • Human Respiratory System -reference: USEPA, 2004
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  • PM Deposition in the Respiratory System -reference: USEPA, 2003
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  • PM Deposition in the Respiratory System One of the major determinants for responses Deposited PM can accumulate, translocate, and be removed Acute effects best represented by deposited dose Chronic effects best represented by retained dose Mechanisms: Interception Impaction Electrostatic interaction Sedimentation Diffusion Site of deposition affects: Severity of local damage Potential for systemic effects Clearance mechanisms
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  • PM Clearance Mechanisms Often classified as absorptive or nonabsorptive Mechanisms: Sneezing Nose wiping and blowing Coughing Mucociliary transport Dissolution and absorption in blood/lymph Uptake by cells Time for clearance ranges from minutes to years -reference: modified from Schlesinger, 1995
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  • Health Effects of PM
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  • Historical PM Events of Health Significance Meuse Valley, Belgium 1930 PM from coal combustion 63 dead, 6000 ill Donora, Pennsylvania 1948 PM from zinc smelter 20 dead, 7000 hospitalized out of a town of 14,000 London, UK 1952 PM from combustion, air inversion 3500-4000 deaths estimated originally, revised to 12,000 potential deaths
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  • Types of PM Health Studies Types of studies Epidemiological Controlled human exposures Animal Molecular/Cellular/Tissue Consistency and coherence of data
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  • PM Components/Parameters of Potential Interest For Health Size Surface area Number Acidity Metals Elemental and organic carbon Mass Size distribution Ions Bioaerosols Other specific toxic constituents
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  • General Comments on PM Health Effects Effects may be from the inherent toxicity of the individual components of PM and/or toxicity due to general PM characteristics Emphasis on PM that reaches the lungs ( PM 10 ) Recent focus on health effects of PM 2.5 Health effects can result from PM PM 10 (e.g. TSP) Effects are generally believed to be less severe unless high inherent particle toxicity or overloading occurs Temporary irritation to the eyes, nose, and throat is a common potential effect Both acute and chronic PM exposures are a concern Health effects associated with PM are nonspecific
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  • Respiratory Effects of PM Acute symptoms: irritation, coughing, wheezing, difficulty taking deep breaths Inflammation Decreased lung function (FEV 1, FVC) Aggravate existing respiratory diseases (e.g. asthma, bronchitis, other COPD) Increases airway reactivity (response to stimuli) Increases susceptibility to respiratory infections Chronic exposure to some types of PM may result in an increased risk of respiratory cancers such as lung cancer ex. Diesel exhaust PM
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  • PM & Cardiac Effects: Challenging Toxicologists To Think Differently My toxicologists are better trained than this cat!!! Otto
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  • Cardiac Effects of PM Change in blood chemistry Can increase blood viscosity which may lead to clotting Inflammation disrupts cell function and activates platelets, which can rupture blood vessel plaques Leads to clotting Cardiac arrhythmias abnormal heart beats Change in heart rate variability (HRV) Decrease in HRV is an early warning sign of potential heart attacks Aggravate existing cardiac diseases Can potentially stimulate heart attacks in sensitive individuals
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  • Cardiac Effects of PM: Change in Blood Chemistry -reference: Nadziejko, et al., 2002 Damage Repair
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  • Modes of Action for Cardiac Effects Underlying mechanism(s) not known Three proposed modes of action: Ultrafine PM ( # PM 0.1 ) enters the blood and directly exerts effects on the heart Pro-inflammatory chemicals triggered in the alveolar region that travel in the blood and exert toxicity in the heart Cardiac effects secondary to respiratory system effects PM can alter autonomic nervous system control of the heart Raises the possibility that heart effects are independent of adverse respiratory effects All three modes are biologically plausible Multiple modes may be working or one mode may predominate depending on the PM characterization
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  • Challenges Evaluating Epidemiological Studies
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  • Association between PM and Heart Attacks -reference: Peters, 2001
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  • Association between PM and Hospital Visits/Admissions -reference: USEPA, 2004
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  • Association between PM and Respiratory Effects -reference: USEPA, 2002
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  • Association between PM and Cardiovascular Effects -reference: USEPA., 2003
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  • Issues Concerning PM & Epidemiological Studies Challenge of quantifying exposure-response relationship Consistent finding: Relatively weak positive association that is not always statistically significant A large number of diverse studies conducted (geographical and temporal variety) Underlying biological mechanism to support epidemiological findings not known Progress made on potential modes of action Ambient monitoring may not be an accurate assessment of personal exposure Confounding sources - other air pollutants responsible?
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  • Who is Sensitive to PM It is estimated that approximately 1/3 of U.S. population is potentially sensitive to PM-related health effects However, at ambient PM levels the majority of the population is not likely to experience health effects or experiences temporary, mild effects Risk from PM is a continuum: high early in life low during late childhood and early adulthood rises as one ages and risk of cardiac and/or respiratory disease increases
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  • Who is Sensitive to PM? People with pre-existing cardiac and/or respiratory diseases Severe cardiac effects can be triggered, some effects may be fatal Respiratory diseases can be exacerbated The elderly Greater prevalence of cardiac and respiratory diseases PM deposition and clearance typically with age Time to recover from effects may be extended Young children Developing systems may be more vulnerable PM exposure is often higher (e.g. more active outdoors) Others people active outdoors during elevated PM Pregnant woman?
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  • Research Needs Determine the best PM parameter(s) for health effects Improve understanding of the mode/mechanism of action Concentration-response estimates Emerging effects: developmental effects Role of co-pollutants in eliciting adverse effects Further understanding of sensitive populations Placing risk from ambient PM exposure in context with other PM exposures (e.g. indoor, personal)
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  • Summary PM is complex Historical events highlight that PM generates health effects, some that may be severe Importance of PM size when discussing deposition and health effects Respiratory and cardiac effects emphasized Sensitive populations for health effects Research needs

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