Dose-dependent effects of submicrometer sulfuric acid aerosol on particle clearance from ciliated human lung airways

Health effects of World Trade Center (WTC) Dust: An unprecedented disaster's inadequate risk management

The World Trade Center (WTC) twin towers in New York City collapsed on 9/11/2001, converting much of the buildings' huge masses into dense dust clouds of particles that settled on the streets and within buildings throughout Lower Manhattan. About 80-90% of the settled WTC Dust, ranging in particle size from ∼2.5 μm upward, was a highly alkaline mixture of crushed concrete, gypsum, and synthetic vitreous fibers (SVFs) that was readily resuspendable by physical disturbance and low-velocity air currents. High concentrations of coarse and supercoarse WTC Dust were inhaled and deposited in the conductive airways in the head and lungs, and subsequently swallowed, causing both physical and chemical irritation to the respiratory and gastroesophageal epithelia. There were both acute and chronic adverse health effects in rescue/recovery workers; cleanup workers; residents; and office workers, especially in those lacking effective personal respiratory protective equipment. The numerous health effects in these people were not those associated with the monitored PM2.5 toxicants, which were present at low concentrations, that is, asbestos fibers, transition and heavy metals, polyaromatic hydrocarbons or PAHs, and dioxins. Attention was never directed at the very high concentrations of the larger-sized and highly alkaline WTC Dust particles that, in retrospect, contained the more likely causal toxicants. Unfortunately, the initial focus of the air quality monitoring and guidance on exposure prevention programs on low-concentration components was never revised. Public agencies need to be better prepared to provide reliable guidance to the public on more appropriate means of exposure assessment, risk assessment, and preventive measures.

Inhalation toxicology methods: the generation and characterization of exposure atmospheres and inhalational exposures

In this unit, the need for laboratory-based inhalation toxicology studies, the historical background on adverse health effects of airborne toxicants, and the benefits of advance planning for the building of analytic options into the study design to maximize the scientific gains to be derived from the investments in the study are outlined. The following methods are described: (1) the generation and characterization of exposure atmospheres for inhalation exposures in humans and laboratory animals; (2) the delivery and distribution into and within whole-body exposure chambers, head-only exposure chambers, face-masks, and mouthpieces or nasal catheters; (3) options for on-line functional assays during and between exposures; and (4) options for serial non-invasive assays of response. In doing so, a description beyond exposures to single agents and simple mixtures is presented, and included are methods for evaluating biological responses to complex environmental mixtures. It is also emphasized that great care should be taken in the design and execution of such studies so that the scientific returns can be maximized both initially, and in follow-up utilization of archived samples of the exposure atmospheres, excreta, and tissues collected for histology.

Toxicological and epidemiological studies of cardiovascular effects of ambient air fine particulate matter (PM2.5) and its chemical components: coherence and public health implications

Recent investigations on PM2.5 constituents' effects in community residents have substantially enhanced our knowledge on the impacts of specific components, especially the HEI-sponsored National Particle Toxicity Component (NPACT) studies at NYU and UW-LRRI that addressed the impact of long-term PM2.5 exposure on cardiovascular disease (CVD) effects. NYU's mouse inhalation studies at five sites showed substantial variations in aortic plaque progression by geographic region that was coherent with the regional variation in annual IHD mortality in the ACS-II cohort, with both the human and mouse responses being primarily attributable to the coal combustion source category. The UW regressions of associations of CVD events and mortality in the WHI cohort, and of CIMT and CAC progression in the MESA cohort, indicated that [Formula: see text] had stronger associations with CVD-related human responses than OC, EC, or Si. The LRRI's mice had CVD-related biomarker responses to [Formula: see text]. NYU also identified components most closely associated with daily hospital admissions (OC, EC, Cu from traffic and Ni and V from residual oil). For daily mortality, they were from coal combustion ([Formula: see text], Se, and As). While the recent NPACT research on PM2.5 components that affect CVD has clearly filled some major knowledge gaps, and helped to define remaining uncertainties, much more knowledge is needed on the effects in other organ systems if we are to identify and characterize the most effective and efficient means for reducing the still considerable adverse health impacts of ambient air PM. More comprehensive speciation data are needed for better definition of human responses.

Functional genomics of chlorine-induced acute lung injury in mice

Acute lung injury can be induced indirectly (e.g., sepsis) or directly (e.g., chlorine inhalation). Because treatment is still limited to supportive measures, mortality remains high ( approximately 74,500 deaths/yr). In the past, accidental (railroad derailments) and intentional (Iraq terrorism) chlorine exposures have led to deaths and hospitalizations from acute lung injury. To better understand the molecular events controlling chlorine-induced acute lung injury, we have developed a functional genomics approach using inbred mice strains. Various mouse strains were exposed to chlorine (45 ppm x 24 h) and survival was monitored. The most divergent strains varied by more than threefold in mean survival time, supporting the likelihood of an underlying genetic basis of susceptibility. These divergent strains are excellent models for additional genetic analysis to identify critical candidate genes controlling chlorine-induced acute lung injury. Gene-targeted mice then could be used to test the functional significance of susceptibility candidate genes, which could be valuable in revealing novel insights into the biology of acute lung injury.

The Kilauea Volcano adult health study

BACKGROUND

Millions of people reside near active volcanoes, yet data are limited on effects to human health. The Kilauea Volcano is the largest point source for sulfur dioxide in the United States, releasing air pollution on nearby communities since 1983.

OBJECTIVE

: The objectives of this study were to provide the first population-based epidemiological estimates and qualitative descriptions of cardiorespiratory health effects associated with volcanic air pollution.

METHODS

An environmental-epidemiological design was used. Exposure levels of Kilauea's air pollutants were determined by environmental sampling. Prevalence estimates of cardiorespiratory health effects in adults were measured (N = 335) and compared between an exposed and nonexposed reference community. Descriptions of the human-environment interaction with the long-standing eruption were recorded from informants in the natural setting.

RESULTS

Ambient and indoor concentrations of volcanic air pollution were above the World Health Organization's recommended exposure levels. There were statistically significant increased odds associated with exposure for self-reported cough, phlegm, rhinorrhea, sore and dry throat, sinus congestion, wheezing, eye irritation, and diagnosed bronchitis. Thirty-five percent of the informants perceived that their health was affected by the eruption, mainly current and former smokers and those with chronic respiratory disease.

DISCUSSION

Hypotheses were supported regarding particulate air pollution and the association with adverse cardiovascular functioning. This emerging environmental health issue is under continuing investigation.

Classification of carcinogenic chemicals in the work area by the German MAK Commission: current examples for the new categories

The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK Commission) introduced an extended classification scheme in 1998. In addition to the traditional three categories still used to date, now called: Category 1 (human carcinogen); Category 2 (animal carcinogen); and Category 3 (suspected carcinogen), two new Categories (4 and 5) were added. Classification of substances into the new Categories 4 and 5 is based on the knowledge of mode of action and the potency of carcinogens. The essential feature of substances classified in the new Categories 4 and 5 is that exposure to these chemicals does not contribute significantly to the risk of cancer to man, provided that an appropriate exposure limit (MAK value) is observed. Chemicals known to act typically by non-genotoxic mechanisms are classified in Category 4. Genotoxic chemicals for which low carcinogenic potency can be assessed on the basis of dose-response relationships and toxicokinetics are classified in Category 5. Since the use of this scheme for 3 years, various chemicals have been classified in one of the new categories. However, in several cases data to sufficiently substantiate a MAK value are missing. Such substances are now classified in a subcategory of Category 3, called Category 3 A, which indicates that further data are required for final classification. Examples are given for classification of dichloromethane into Category 3 A, chloroform and sulfuric acid into Category 4 and ethanol into Category 5.

Acute exposure to acid fog. Effects on mucociliary clearance

Submicrometric sulfuric acid (H2SO4) aerosol can affect mucociliary clearance without eliciting irritative symptoms or changes in pulmonary function. The effect of larger fog droplets containing H2SO4 on mucociliary clearance is unknown. We quantified mucociliary clearance from the trachea (n = 4) and small airways (n = 7) of young healthy male adults after an acute exposure to H2SO4 fog (MMAD = 10.3 microns; pH = 2.0; liquid water content = 481 +/- 65 mg/m3; osmolarity = 30 mOsm). Acid fog (AF) or saline fog (SF) (10.9 microns; 492 +/- 116 mg/m3; 30 mOsm) was administered for 40 min of unencumbered breathing (no mouth-piece) at rest and for 20 min of exercise sufficient to produce oronasal breathing. Fog exposures were followed by a methacholine (MCh) challenge (a measure of airway reactivity) or inhalation of technetium-99M radioaerosol (MMAD = 3.4 microns) on 2 study days each. Changes in symptoms and forced ventilatory function were also assessed. Clearance was quantified from computer-assisted analyses of gamma camera images of the lower respiratory tract in terms of %removal/min of the radiolabel from the trachea 25 min after inhalation and from the outer zone of the right lung after 1.9 to 3 h. Symptoms, forced ventilatory function, and MCh response were unaffected by either fog. Tracheal clearance was more rapid in four of four subjects after AF (0.83 +/- 1.58% removal/min) compared with that after SF (-0.54 +/- 0.85% removal/min). Outer zone clearance was more rapid in six of seven subjects after AF (0.22 +/- 0.15% removal/min) compared with that after SF (0.01 +/- 0.09% removal/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Epidemiologic and toxicologic evidence for chronic health effects and the underlying biologic mechanisms involved in sub-lethal exposures to acidic pollutants

Since the 1880s, a disparate and extensive literature has evolved examining the biologic effects of acidification on cells. More recently, effects on the health of human and other species of acidic agents contained, for example, in pollutants have been suggested, particularly relating to long-term exposures. This paper provides a review of the epidemiologic and toxicologic evidence concerning health effects--particularly carcinogenicity--attributable to sub-lethal acid exposure. Underlying biologic mechanisms that explain adverse health outcomes include pH modulation of toxicity for a number of xenobiotics (including carcinogens, genotoxins, and teratogens), and low-pH-induced changes of cells involving, for example, alterations in mitotic and enzyme regulation. More focused research is recommended to test the relationship between long-term exposures to acidic agents (with a consequent lowered cellular pH) and various health effects.

Airborne particles, their use in the respiratory system to measure air flow, function, and clearance

Nonhygroscopic monodisperse particles can be used to estimate airway dimensions within chosen regions of the respiratory tract. These dimensions correspond well with those measured in inflation-fixed lungs. The dispersion of a bolus of airborne particles on inhalation and exhalation is very sensitive to the dimensions of the airways through which the bolus passes, yielding indices of dispersion that provide sensitive indicators of changes in airway dimensions, eg, with smoking. The rates of clearance of particles from the lungs are determined using gamma-labelled particles whose lung retention is determined by external measurements. There are major differences between the deep lung and the ciliated airways. Changes in clearance rates are caused by disease or inhaled intoxicants such as cigarette smoke. At lower levels of irritant exposure, an acceleration of clearance rate is observed, while higher doses and longer periods of exposure produce decreased rates. It is suggested that aerosol techniques may have useful clinical applications; approaches are suggested for such applications.

Exposure-response relationship of bronchial mucociliary clearance in rabbits following acute inhalations of sulfuric acid mist

Eight rabbits underwent 1 h oral inhalations of submicrometer sulfuric acid mist at concentrations ranging from approx. 100-1084 micrograms/m3, followed by measurement of the mucociliary clearance of a tracer aerosol from the bronchial tree. These data, plus those from a previous study, were used to construct an exposure concentration-response relationship for alterations in clearance produced by H2SO4. The response pattern is characterized by transient acceleration of clearance at low concentration exposures, and retardation at higher concentrations. In addition, comparison of these results with those from a similar study using human volunteers supports use of the rabbit as an appropriate model for studying mucociliary clearance alterations produced by inhaled irritants.