Human Health Effects of Particulate Human Health Effects of Particulate Matter (PM)Matter (PM)
Nathan Pechacek, M.S.
Toxicology Section
Texas Commission on Environmental Quality
512-239-1336
PM10 ~100 ug/m3
PM2.5 ~20 ug/m3
PM10 ~400-1000 ug/m3, PM2.5 ~60-140 ug/m3
Presentation OutlinePresentation Outline
Background informationHealth effectsChallenges of epidemiological studiesSensitive populationsResearch needsSummary
Background Information on Background Information on PM and the Respiratory PM and the Respiratory
SystemSystem
Particulate MatterParticulate Matter
Complex substance:– Sources– Composition– Size– Travel distance– Time spent airborne
-reference: Brook, et al. 2004
Human Human RespiratoryRespiratory System System
-reference: USEPA, 2004
PM Deposition in the PM Deposition in the Respiratory SystemRespiratory System
-reference: USEPA, 2003
PM Deposition in the PM Deposition in the Respiratory SystemRespiratory 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
PM Clearance MechanismsPM 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
Health Effects of PMHealth Effects of PM
Historical PM Events of Health Historical PM Events of Health SignificanceSignificance
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
Types of PM Health StudiesTypes of PM Health StudiesTypes of studies
– Epidemiological– Controlled human exposures– Animal– Molecular/Cellular/Tissue
Consistency and coherence of data
PM Components/Parameters PM Components/Parameters of Potential Interest For Healthof Potential Interest For Health Size Surface area Number Acidity Metals Elemental and organic
carbon
Mass Size distribution Ions Bioaerosols Other specific toxic
constituents
General Comments on PM General Comments on PM Health EffectsHealth 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 (PM10)– Recent focus on health effects of PM2.5
– Health effects can result from PM PM10 (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
Respiratory Effects of PMRespiratory Effects of PM Acute symptoms: irritation, coughing, wheezing, difficulty
taking deep breaths Inflammation Decreased lung function (FEV1, 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
PM & Cardiac Effects: Challenging PM & Cardiac Effects: Challenging Toxicologists To Think DifferentlyToxicologists To Think Differently
My toxicologists are better trained than this cat!!!
Otto
Cardiac Effects of PMCardiac 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
Cardiac Effects of PM: Cardiac Effects of PM: Change in Blood ChemistryChange in Blood Chemistry
-reference: Nadziejko, et al., 2002
Damage
Repair
Modes of Action forModes of Action for Cardiac Effects Cardiac Effects
Underlying mechanism(s) not known Three proposed modes of action:
– Ultrafine PM (PM0.1 ) 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
Challenges Evaluating Challenges Evaluating Epidemiological StudiesEpidemiological Studies
Association between PM Association between PM and Heart Attacksand Heart Attacks
-reference: Peters, 2001
Association between PM and Association between PM and Hospital Visits/AdmissionsHospital Visits/Admissions
-reference: USEPA, 2004
Association between PM and Association between PM and Respiratory EffectsRespiratory Effects
-reference: USEPA, 2002
Association between PM and Association between PM and Cardiovascular EffectsCardiovascular Effects
-reference: USEPA., 2003
Issues Concerning PM & Issues Concerning PM & Epidemiological StudiesEpidemiological 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?
Who is Sensitive to PMWho 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
Who is Sensitive to PM?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?
Research NeedsResearch 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)
SummarySummary 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
