Occupational and environmental aerosol exposure assessment: a scientific journey from the past, through the present and into the future.

This paper reviews how aerosol exposure assessment, for people in both working and living environments, has evolved over the years. It charts the main scientific developments that led to progressively improved ways of thinking and methods to assess exposure to airborne particulate matter in a manner more relevant to human health. It has been a long scientific journey as one generation of pioneering contributors has handed off to the next.

Performance study of personal inhalable aerosol samplers at ultra-low wind speeds.

The assessment of personal inhalable aerosol samplers in a controlled laboratory setting has not previously been carried out at the ultra-low wind speed conditions that represent most modern workplaces. There is currently some concern about whether the existing inhalable aerosol convention is appropriate at these low wind speeds and an alternative has been suggested. It was therefore important to assess the performance of the most common personal samplers used to collect the inhalable aerosol fraction, especially those that were designed to match the original curve.

Sampling conventions for estimating ultrafine and fine aerosol particle deposition in the human respiratory tract.

Objectives: To provide targets for personal samplers designed for estimating particle deposition at distinct locations in the body, accounting if necessary for inter- and intra-person variation.

Proposal: Ultrafine and fine aerosol sampling conventions are proposed for approximating the deposition efficiency for five distinct loci of the respiratory tract. The 2 × 5 = 10 conventions represent averages over variation in physical activity level, posture, sex, and breathing mode.

Proposed modification to the inhalable aerosol convention applicable to realistic workplace wind speeds.

The current convention for sampling inhalable aerosols was based on several mannequin studies performed in wind tunnels at wind speeds between 0.5 and 4 m s(-1). In reality, as we now know, the wind speed in most modern indoor working environments is generally at or below ∼0.

Experimental methods to determine inhalability and personal sampler performance for aerosols in ultra-low windspeed environments.

Most previous experiments of aerosol inhalability as it relates to particle aerodynamic diameter were conducted in wind tunnels for windspeeds greater than 0.5 m s(-1). While that body of work was used to establish an inhalable aerosol convention, results from studies in calm air chambers (for essentially zero windspeed) are being discussed as the basis of a modified criterion.

Visualization of the airflow around a life-sized, heated, breathing mannequin at ultralow windspeeds.

During the past two decades, there has been considerable progress in developing particle size-selective criteria for aerosol sampling and exposure assessment that relate more realistically to actual human exposures than previously. An important aspect has been the aspiration efficiency-the 'inhalability'-with which particles enter through the nose and mouth of aerosol-exposed individuals during breathing. Most of the reported experiments to determine inhalability have been conducted in wind tunnels with life-sized, breathing mannequins, for windspeeds from 0.

A modified Marple-type cascade impactor for assessing aerosol particle size distributions in workplaces.

Knowledge of the particle size distributions for workplace aerosols is invaluable in the assessment of aerosol-related health effects. Cascade impactors have been widely used for obtaining such information, including a small number that have been developed as personal samplers of the type that can be used for the assessment of the exposures of individual workers. Common limitations for most samplers of this type have been that (a) the aspiration efficiency has not been well defined (leading to biases in particle size distribution measurement), and (b) the range of particle size has been constrained by particle bounce in impactors for particle sizes beyond about 20 micro m.

Species-specific inhalable exposures in the nickel industry: a new approach for deriving inhalation occupational exposure limits.

The American Conference of Governmental Industrial Hygienists (ACGIH) and some regulatory authorities have revised their exposure limits for nickel and nickel compounds in workplaces based upon new sampling standards for inhalable nickel exposures. Others may be in the process of doing so. Safe standards for workplace exposures should utilize the most up-to-date health data on individual nickel species and should incorporate the principles of new sampling conventions that have been developed over the recent decades.

Testing personal inhalable aerosol samplers: a suggested improved protocol based on new scientific knowledge.

In 2002 the Comité Européen Normalisation (CEN) published its document Workplace atmospheres-assessment of performance of instruments for measurement of airborne particle concentrations (EN 13205) that describes a standard protocol by which to carry out the testing and validation of personal aerosol samplers of the type widely used for occupational aerosol exposure assessment. It emerged from more than a decade of discussion and a large body of research experience involving several laboratories. The protocol that is described, however, still poses significant technical and economic challenges, not least because it involves laborious-and hence costly-procedures in large, specialized wind tunnel facilities.

Health-related aerosol measurement: a review of existing sampling criteria and proposals for new ones.

Interest in particle size-selective sampling for aerosols in working and ambient living environments began in the early 1900s when it became apparent that the penetration into-and deposition in-the respiratory tract of aerosol-exposed humans of inhaled particles was dependent on particle size. Coarse particles tended to be filtered out during inhalation and in the upper parts of the respiratory tract, so only progressively smaller particles penetrated down to the deep regions of the lung. Over time, following experimental studies with 'breathing' mannequins in wind tunnels and with human volunteer subjects in the laboratory, a clear picture has emerged of the physical, physiological and anatomical factors that control the extent to which particles may or may not reach certain parts of the respiratory tract.

Graduate education in occupational hygiene: a rational framework.

Occupational hygiene has been an important part of occupational health since it first emerged after World War II as the science and art that deals with the anticipation, recognition, evaluation and control of human exposures to hazards in the working environment. A need exists for well-qualified professionals who can not only respond to hazards that are currently known and understood, but also to ones that are not yet known or understood. For this, graduate-level academic programs in occupational hygiene must go beyond the training of skills and imparting of facts.

Environmental health implications of global climate change.

This paper reviews the background that has led to the now almost-universally held opinion in the scientific community that global climate change is occurring and is inescapably linked with anthropogenic activity. The potential implications to human health are considerable and very diverse. These include, for example, the increased direct impacts of heat and of rises in sea level, exacerbated air and water-borne harmful agents, and--associated with all the preceding--the emergence of environmental refugees.

An exploratory study of changing occupational injury risk during the closure of industrial operations.

Companies go out of business on a regular basis, and industrial plants close as a result. Various social, economic and interpersonal dynamics accompany such events. Environmental health and safety (EH&S) aspects are not exempt from those dynamics during a programmed closing of a manufacturing operation.

The orientation-averaged aspiration efficiency of IOM-like personal aerosol samplers mounted on bluff bodies.

This paper describes two sets of experiments that were intended to characterize the orientation-averaged aspiration efficiencies of IOM samplers mounted on rotating bluff bodies. IOM samplers were mounted on simplified, three-dimensional rectangular bluff bodies that were rotated horizontally at a constant rate. Orientation-averaged aspiration efficiencies (A360) were measured as a function of Stokes' number (St), velocity ratio (R) and dimension ratio (r).

Expert judgment and occupational hygiene: application to aerosol speciation in the nickel primary production industry.

In many situations characterized by sparse data, occupational hygienists have used subjective judgments that are claimed to be derived from their experience and knowledge. While this practice is widespread, there has been no systematic study of 'expert judgment' or the 'art' of occupational hygiene. Indeed, there is a need to address the question of whether there is such a thing as 'expert opinion' in occupational hygiene that is broadly shared by practicing professionals.

Filter and cassette mass instability in ascertaining the limit of detection of inhalable airborne particulates.

In the gravimetric assessment of workplace aerosols, there is an increasing need to confidently measure smaller and smaller collected masses. To do this, it is important to know both the limit of detection (LOD) and limit of quantification (LOQ) of the analysis performed, determined by the weighing imprecision of blank samples. Of particular current interest is the measurement of inhalable aerosols, as defined for many substances in the American Conference of Governmental Industrial Hygienists threshold limit values list.

Critical evaluation of historical occupational aerosol exposure records: applications to nickel and lead.

Published or unpublished data sets on individual occupational exposure situations are frequently combined and used for some wider purpose, either hazard evaluation or standards setting. This paper describes a model by which such individual data sets for occupational aerosol exposures might be evaluated in terms of their usefulness in this regard. For workplace aerosols, the model is centered around the particle size-selective framework for aerosol exposure assessment that has emerged in recent years as a rational basis for standards setting.

New experimental methods for the development and evaluation of aerosol samplers.

An understanding of the scaling laws governing aerosol sampler performance leads to new options for testing aerosol samplers at small scale in a small laboratory wind tunnel. Two methods are described in this paper. The first involves an extension of what is referred to as the "conventional" approach, in which scaled aerosol sampler systems are tested in a small wind tunnel while exposed to relatively monodisperse aerosols.

Personal sampling for inhalable aerosol exposures of carbon black manufacturing industry workers.

The study was concerned with the measurement of inhalable aerosol exposures in the carbon black production industry. The primary goal of the study was to determine the extent to which inhalable aerosol exposure, as measured by the Institute of Occupational Medicine (IOM) personal inhalable sampling head, compared to "total" aerosol exposure, as measured by traditional methodology. A secondary objective was the evaluation of another inhalable aerosol sampler for carbon black aerosol measurement.