What Is the Potential Measurement Error in Occupational Exposure Studies?

ABSTRACT

This paper demonstrates statistical methods that estimate measurement error from available industrial hygiene data. Errors in measuring a continuous exposure variable may arise when all individuals in a work area are assigned the same exposure. An example is when the mean of exposure measurements obtained on a sample of individuals is assigned to all workers with similar jobs. This may lead to inaccurate point and interval estimates in exposure-response modeling. A method of simulating the distribution of true (i.e., unobserved) individual exposures is described in order to estimate the mean and variance of measurement error. The minimum variance unbiased estimator approximates the mean of lognormally distributed exposure measurements. The distribution of true individual exposures is approximated by the distribution of simulated estimates of mean exposure. The methodology is illustrated by exposure data from work areas manufacturing refractory ceramic fiber (RCF) and RCF products. Results show that exposure is slightly underestimated in work areas with between 25 and 113 exposure measurements; measurement error variance averages about 1.3% of the total variance.     

Simulation of the daily average PM10 concentrations at Ta-Liao with Box–Jenkins time series models and multivariate analysis

Southern Taiwan has experienced severe PM₁₀ problems for over a decade. The present paper describes the establishment of a simulation model for the daily average PM₁₀ concentrations at Ta-Liao, southern Taiwan. The study used a regression with time series error models (RTSE models) (multivariate ARIMA time series model), including an explanatory variable resulting from principal component analyses to complete the PM₁₀ simulation. Factor 1 estimated from the factor analyses explained the variance of 44–49%, which indicated the important contribution from the neighbor-city PM₁₀ at Mei-Nung, Lin-Yuang, Zuoying, Chao-Chou, local ozone and NOx. Factor 1 can be interpreted with regional PM₁₀ plus photochemical reactions. To improve the predictability of extremely high PM₁₀, different results from the principal component analysis were introduced to the RTSE models. We constructed four kinds of RTSE models: RTSE model without PC, with PC4S (PM₁₀ at Mei-Nung, Lin-Yuang, Zuoying, and Chao-Chou), with PCTL (meteorological variables and co-pollutants at Ta-Liao), and with PCTL4S (the combination of the above two) and evaluated the statistics model performance. Ozone, dew point temperature, NOx, wind speed, wind directions, and the PC trigger were the significant variables in the RTSE models most of time. When the neighbor-city PM₁₀ was included in the PC trigger, the predictability was apparently improved. The closeness of fit with the inclusion of PC4S and PCTL4S was improved by reducing SEE from 0.117 to 0.092. Using the RTSE models with PC4S or PCTL4S, POD was improved by an increase of 33%, FAR was reduced 30%, and CSI was increased 39%, when simulating the daily average PM₁₀ > 150 μg m^?3. Evidently we need to survey source impacts prior to establishing a simulation model. Factor analysis is a useful method to investigate sources that contributed PM₁₀ to a target site prior to establishing a simulation model.     

Laboratory and field evidence of sex-biased movement in the invasive round goby

Activity levels are modulated by trade-offs between reducing predation risk and the need to move in order to find food or mates. Because these trade-offs affect males and females differently, many species show sex-specific movement, dispersal patterns, and spatial navigation capacities, with the sex that gains the most from territory ownership often dispersing less. Unlike mammals and birds, sex differences in movement among fishes remain poorly studied, and the connections between tests of movement propensity in the laboratory and in the field are rarely made. Here, we examine the differences in movement between male and female round goby (Neogobius melanostomus) in both laboratory and field settings. This fish species is invasive in North America and currently undergoing further range expansions. In the laboratory, round goby males were more active and explored a novel environment more readily than did females. A large-scale mark–recapture study in Lake Ontario over two years revealed that males moved more than females between years, but there were no within-year sex differences. Thus, round goby display male-biased movement patterns, providing a comparison point to dispersal patterns in other taxa. Understanding sex-specific movement of round goby in the field will also help predict dispersal and population dynamics, both in areas where round goby have already become established and where they are continuing to invade.     

Errant corporations, diffuse responsibilities, and the environment: ethical issues in the Orica case study

The papers in this volume deal with various aspects of the HCB legacy at the Orica plant at Botany. Whether explicitly or implicitly, they are concerned with questions of ethics; with the just distribution of burdens and benefits; with just processes for disposing of dangerous industrial waste; and with a just custodianship of the Botany environment. These ethical issues illustrate the difficulty of securing corporate accountability, and the elusiveness of responsibility within organisations. This paper reflects on some of the issues for ethics raised by the Orica case and their significance for corporate ethics.     

Mercury accumulation in surface sediments of salt marshes of the Bay of Fundy

Mercury contamination in Canada's Bay of Fundy is a priority concern because of elevated levels observed in fish, birds and wildlife. Salt marshes constitute an important part of the Bay's coastline and are potential stores of mercury for the region. We measured the amount of mercury accumulated over a 5-yr period from 1997 to 2002 in surface sediments of seven salt marshes along the New Brunswick coast of the Bay. The seven study sites extended from outer to inner Bay, spanning a gradient in tidal range (6-12 m) and sediment characteristics such as %LOI (4-29%) and sediment deposition rate (0.27-1.76 cm yr(-1)). In each study site, mercury was measured in low and high marsh areas. Sediment mercury concentrations ranged from 7 to 79 ng g(-1) and loading rates ranged from 0.1 to 1.1 mg m(-2). Total estimated 5-yr storage of mercury in salt marsh sediments of the Bay is 854+/-465 kg. We also compared sediment mercury loading to atmospheric inputs measured at a deposition monitoring station operating in New Brunswick from 1997 to 2002 and found that direct atmospheric deposition appears to be a minor input of mercury to these sediments. We are unaware of documentation of mercury loading in salt marshes on a bay-wide scale and over a constrained (5-yr) time period elsewhere.     

UNMIX modeling of ambient PM(2.5) near an interstate highway in Cincinnati, OH, USA

The "Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS)" is underway to determine if infants who are exposed to diesel engine exhaust particles are at an increased risk for atopy and atopic respiratory disorders, and to determine if this effect is magnified in a genetically at risk population. In support of this study, a methodology has been developed to allocate local traffic source contributions to ambient PM(2.5) in the Cincinnati airshed. As a first step towards this allocation, UNMIX was used to generate factors for ambient PM(2.5) at two sites near at interstate highway. Procedures adopted to collect, analyze and prepare the data sets to run UNMIX are described. The factors attributed to traffic sources were similar for the two sites. These factors were also similar to locally measured truck engine-exhaust enriched ambient profiles. The temporal variation of the factors was analyzed with clear differences observed between factors attributed to traffic sources and combustion-related regional secondary sources.     

Electrostatic enhancement of moving-bed granular filtration

The electrostatic granular filter developed by Combustion Power Company combines a moving-bed filter with an electrostatic grid for high-efficiency collection of particulate. The coulomb charge occurring naturally on particulate from combustion or other processes in which tribocharging occurs is sufficient such that imposition of an electric field substantially enhances mechanical collection in the packed filter. A mathematical model is presented which accounts for the major parameters affecting electrostatic performance. Experimental data developed in an industrial unit retrofitted with electrostatic equipment and a pilot-scale filter demonstrates dramatic improvement in opacity and outlet loading; the industrial unit achieved 99% collection efficiency with less that 4 Iwd (1kPa) pressure drop. Data from the pilot-scale filter has shown that collection of micron-size particulate is especially enhanced with the electric field and has confirmed the 99% overall collection capability demonstrated in the industrial unit. The design of a 420,000 acfm (1200 m³/min) system being installed at Weyerhaeuser Company's Longview, Washington plant is also discussed.     

Applying a TQM framework to the public policy process: Part I—the framework

In Part I of this article, a TQM framework is described that can be used to analyze as well as manage the public policy process. Key elements of the framework include leadership, issues analysis, goal and policy development, strategic vehicles, implementation, indicators and outcomes, and stakeholder review. The framework can be used to analyze public policy cycles, predict future issues and outcomes, and develop more sustainable approaches to manage linked economic, environmental, and societal issues. In Part II, the framework is used to examine the effectiveness of management of environmental issues in the Great Lakes region over the past three decades and to demonstrate the need for a more integrated approach to regional management.     

Engaging your networks

The following is an excerpt form Grace Wever's new book Strategic Environment Management: Using TQEM and ISO 14000 for Competitive Advantage (John Wiley & Sons Inc., 1996). In this chapter entitled “Engaging Your Networks,” she shows how companies can “design-in” satisfaction through supply chain partnerships and join hands productively with customers and stakeholders to address EHS issues of mutual concern. Guidelines for value-added partnering are included as well as many illustrative company samples.     

Secondary materials and international trade

The paper develops the international trade dimensions of recycling. It begins by outlining the sources of demand and supply that determine the volume, composition and direction of trade in waste materials. The model is intended to describe factors affecting international flows of any type of secondary material, although its usefulness in an empirical context is restricted in many cases by data limitations and complex lag structures on the supply side. Parts of the model are then applied to the case of waste paper, focusing on observed differences in national recycling rates and the role of trade in reconciling those differences.