Establishing the Exposure Assessment Strategy

Transcription

1 Establishing the Exposure Assessment Strategy 1

2 Professional Judgment of Industrial Hygienists To apply knowledge learned from formal education, observation, experimentation, inference, and analogy to estimate exposure in nearly any scenario, and to set a working exposure limit. Professional judgment is vital to identifying SEGs. It is also essential for making judgments, in planning monitoring campaigns, and in recommending changes needed to reduce exposures to acceptable levels through health hazards and control. 2

3 Nonroutine Operation Features of nonroutine operations are: Short lead time Short duration Transient work force Nonrepetitiveness Variable work sites Poorly defined tasks Variable work practices Multiple environmental agents Limited health effects data on the environmental agents For application to nonroutine operations, the exposure assessment strategy must be recognized as a flexible tool. 3

4 Goals of Exposure Assessment Two general exposure assessment strategies comprehensive exposure assessment strategy compliance exposure assessment strategy Organizations are encouraged to adopt the comprehensive strategy. To assess all exposures for all workers on all days. In addition to ensure compliance with existing occupational exposure limits (OELs), it also provides an understanding of the day-to-day distribution of exposures. 4

5 Goals of Comprehensive Exposure Assessment Characterize exposure to all potentially hazardous chemical, physical and biological agents, including those without formal OELs. Characterize the exposure intensity and temporal (hour-tohour/day-to-day) variability faced by all workers. Assess the potential risks (harmful effects and noncompliance). Prioritize and control exposures that present unacceptable risks. Identify exposures that need additional information gathering (e.g., baseline monitoring). Document exposures and control efforts, and communicate exposure assessment findings to all relevant workers and personnel. Maintain a historical record of exposures for all workers. Accomplish the preceding steps with efficient and effective allocation of time and resources. 5

6 Goal of Compliance Exposure Assessment To assess whether workers exposures are in compliance with OELs. Worst-case exposure monitoring The compliance strategy provide little insight into the day-to-day variation in exposure levels and is not useful for the development of exposure histories that accurately reflect exposures and health risk. 6

7 Written Exposure Assessment Program A written exposure assessment program is an important reference tool for documenting how an organization will administer occupational exposure assessments. To specify the strategies, methods, and criteria used in conducting the assessments. 7

8 Key Things Addressed in a Written Exposure Assessment Program Goals of the occupational exposure assessment program; Role and responsibilities of the industrial hygienists and other technical support staff; Methods for systematized information gathering to form a basic characterization of the workplace, work force, and environmental agents; Methods for defining SEGs and the exposure profile for each group; Criteria for making a judgment as to whether the exposure profile for a SEG is acceptable, unacceptable, or uncertain; Systems for prioritizing and gathering the additional information needed to better characterize uncertain exposures and make a more confident judgment about their acceptability; Exposure thresholds and criteria for conducting monitoring; A system for ensuring that unacceptable exposures are prioritized and controlled; Systems for communicating and documenting exposure assessment findings and hazard control recommendation; systems and criteria for periodic reassessment of workplace exposures. 8

9 Introduction to Exposure Assessment Approaches 9

10 Basic Information Required for Conducting Exposure Assessment Questions needed to be answered: What are the agents used in the work environment? What are the occupational exposures limits (OELs) for each agent? What are the health effects associated with excessive exposure to the agents? How are workers in the work environment involved with each of the agents? What are the key operations and activities that pose the greatest potential for exposure to the agents? Basic information needed: workplace characterization workforce characterization agent characterization 10

11 Workplace Characterization Workplace layout to identify the sources of potential exposure, locations of chemicals and tasks, and ventilation and other control methods. Written descriptions of processes and activities to explain what takes place in the work area. 11

12 Workforce Characterization Job classifications (job categories or work groups) job titles operating units work departments number of workers included Job descriptions work duties task analysis specific process areas work activities work frequency time duration Demographic information work history outside occupation life-style information (smoking habit, alcohol drinking, etc.) 12

13 Agent Characterization Agent inventory Quantity used Chemical and physical properties Health effects at least obtain the Material Safety Data Sheets ( MSDS) for agents other toxicological information 13

14 Exposure Assessment Approaches Direct approaches direct measurements of exposure concerns to take a representative sample of the study population for exposure measurements (statistical sampling technique) routes of exposure (multimedia monitoring) to select an appropriate exposure metric (air samples, biological markers, etc.) to characterize exposure time Indirect approaches to understand the basic relationship between causative variables (or factors) and resulting exposures. to use exposure modeling approaches to characterize individual or population exposure profiles and distributions. 14

15 Direct Approaches Exposure distribution lognormal distribution Exposure sampling Exposure variability Environmental versus analytical variability Homogeneous exposure grouping between- and within-individual variability Exposure correlation in time and space time series spatial analysis Uncertainty and sensitivity analysis 15

16 Indirect Approaches Microenvironment defined as a location of homogeneous pollutant concentration that a person occupies for some finite period of time. Exposure dispersion models Time-activity patterns Source-receptor models Job-exposure matrix 16