OVERVIEW OF INDUSTRIAL HYGIENE PRINCIPLES OFEVALUATING WORKER EXPOSURE
DEFINITIONIndustrial Hygiene (IH) is that sciencedevoted to the anticipation, recognition,measurement, evaluation, and control ofadverse occupational stresses or agentswhich could cause sickness and impairedhealth among workers and thecommunity. The basic goal of IH (i.e.occupational hygiene) is to promote asafe and healthful work environment.
OCCUPATIONAL HYGIENEThe science and art of anticipating,recognizing, evaluating, and controllinghealth hazards in the workplace. Thepurpose of this introduction is to provide anunderstanding of the general principles ofevaluating worker exposures in theindustrial environment.
IH FOCUS1. Hazardous agents in workplace2. Health effects associated with excessive exposures3. Occupational Exposure Limits (OELs) for each agent4. Workforce organization and staffing5. Significant sources of exposure; tasks and work procedures involved6. Control measures
IH ELEMENTS Anticipation Recognition Evaluation Control
ANTICIPATIONExpectation of potential health hazards isgenerally more difficult for the entry-level,inexperienced occupational hygienist since skills inanticipation generally increase with experience.Ability to recognize potential health hazards aswell as knowledge of scientific developments, newtechnologies, and regulatory requirements, etc.
RECOGNITIONRequires knowledge and understanding ofworkplace environmental stresses and effects onhealth of the worker related to processes andcontrol measures; inventory of chemical,biological, and physical hazards; potentialchemical hazards are determined by toxicity andalso conditions of use. Involves collection ofavailable information along with the application ofIH principles.
RECOGNITIONDetailed information to be obtainedregarding types of hazardous materialsused, type of job operation, workerexposures and patterns, levels of aircontaminants, exposure duration, controlmeasures, etc. Consult product information. Develop workplace characterization whichresults in defining “exposure groups” forsame tasks/similar manner.
TOXICITY VS. HAZARD Toxicity is the capacity of a material to produce injury or harm to living tissue when the chemical has reached a sufficient concentration at a certain site in the human body. Hazard is the probability that this concentration will occur within the body; affected by many factor/elements generally related to conditions of use.
EVALUATIONInvolves observation as well as monitoringand use of analytical methods required todetect the extent of exposure; decision-making process resulting in an opinion on thedegree of health hazards and/or stressorsthat exist; determine significance (e.g.subjective/objective judgment); extent ofpotential health hazards based oncomparisons of environmental measurementswith current governmental regulations andrecommended technical guidelines.
EFFECTIVE EVALUATION Utilize a multi-disciplinary approach including knowledge-based technical information. Contributions include: occupational hygiene, chemistry, engineering, health physics, medicine, epidemiology, toxicology, and nursing disciplines as well as management and manufacturing expertise. Integrate knowledge and develop control strategies for potential risk limitation. Consider team-based efforts of personnel.
EVALUATION Exposure assessment: initial qualitative method for prioritization; then, semi-quantitative (i.e. mathematical modeling) or quantitative (i.e. monitoring) methodologies. Air monitoring can be involved for quantitative assessment; breathing zone exposures preferred. On-going process: feedback from multiple sources of information; refine exposure estimates; evaluate control effectiveness; priorities change!
EXPOSURE ASSESSMENT Control exposures Compliance determinations Program management (i.e. respiratory; hearing/noise; medical surveillance, etc.) Epidemiologic studies Health complaint investigations Risk assessment Proposed change evaluations to process
CONTROLInvolves the reduction of environmentalstresses to levels that the worker cantolerate without impairment of health orproductivity; various general controlmethods employed for accomplishments inan efficient and effective manner.
CONTROLDefined as the adjustment or regulation ofan operation to meet a standard orguideline, the reduction or prevention ofcontaminant release, and the ability tocontain a stressor/hazard.
CONTROL METHODS Engineering – remove the hazard; should be primarily considered. Administrative – reduce exposures through scheduling/job rotation; housekeeping; employee training; not generally favored. Personal Protective Equipment (PPE) – use should be secondary to design and implementation of engineering controls.
ADMINISTRATIVE CONTROLSEXAMPLES:- Arranging work schedules and therelated frequence/duration to limitemployee exposures to health hazards.- Transferring employees at PELs to an environment where additional exposure is not anticipated.- Housekeeping; preventive maintenance.
ADMINISTRATIVE CONTROLSAdministrative controls must be designedonly by knowledgeable health and safetyprofessionals, and used cautiously.Not as satisfactory as engineering controlsand have been criticized as a means ofspreading exposures instead of reducing oreliminating personal exposures.
PPEPPE may be used to protect the workerwhen it is not feasible to render the workingenvironment completely safe. Examples:eye/foot/head protection, gloves,respirators.Considered a secondary control method toengineering and administrative controls andshould be used as a last resort.
EFFECTIVE IH PROGRAMApplies knowledge to the anticipation andrecognition of health hazards arising out ofwork operations and processes, evaluationand measurement of the magnitude of thehazard based on past experience andstudy, and control of the occupationalhazards.
OTHER HAZARDS Confined Spaces Waste Management Lab Health and Safety Emergency Planning Etc. . .
EXPOSURE ASSESSMENTDetermination or estimation of the magnitude, frequency, duration, and route of exposure. Determine purpose and scope of survey Become familiar with process operations Perform the preliminary, qualitative survey Conduct workplace monitoring as a quantitative evaluation Interpret the sampling results.
TYPES OF EVALUATIONS Comprehensive exposure assessment to identify and quantify health hazards Assess compliance with regulatory standards and/or technical guidelines Review exposures based on complaints + Exposure assessment for medical and epidemiological studies + Determine effectiveness of engineering and/ or administrative controls +
COMPREHENSIVE EXPOSURE ASSESSMENTPrimary objective is to determine theacceptability of exposures to health hazardsfor all workers in designated work areas orfor specific operations. Based on identification andquantification/estimation of exposures toworkplace stressors, then use of walk-throughsurvey procedures for hazard identification,and subsequently, evaluation techniques toestimate employee exposure levels areemployed.
COMPLIANCE SURVEYExposure to stressors are quantified andevaluated by comparison to published healthstandards, Permissible Exposure Limits(PELs) or technical recommended guidelinessuch as American Conference ofGovernmental Industrial Hygienists (ACGIH)Threshold Limit Values (TLVs).Determine compliance vs. non-compliance.
PROCESS OPERATIONS Physical facility layout Process description and steps Inventory of process stressors/hazards Worker job classifications Worker health status Control measures in place Results from past evaluations Other associated process hazards
PROCESS METHODOLOGYInformation obtained through interviews,personal/visual observations, technicalprocess information, and record reviews.A walk-through survey is an importantmethodology to understand, verify, and/ormodify documentation; look for potentialsources of health hazards and chemical aircontaminants and physical agents.
INVENTORY Hazard/Stressor listing for identification Chemical and physical agents Toxicological information; reference sources Occupational Exposure Limits (OELs) e.g. OSHA PELs, ACGIH TLVs, NIOSH RELs, AIHA WEELs, ANSI, NIOSH Pocket Guide
JOB CLASSIFICATIONS/ WORK HEALTH STATUSFormal job descriptions, and personnelinterviews with employees/supervisors.Worker health status – medical surveillancefor health hazard recognition and workplacelogs of incidents/injuries/illnesses forassistance with stressor identification.
PAST EVALUATIONS/IDENTIFY POTENTIAL HAZARDSReview of past occupational hygiene orrelated evaluations. Determine: timeelapsed; process changes, identification ofsignificant problems, and/or other indicators.Personnel interviews and site review. Getworkers involved in the familiarization stepof a survey to assist with acceptance.
PRELIMINARY ASSESSMENT - QUALITATIVEFamiliarity with process/operation toqualitatively evaluate magnitude ofstressors without benefit of instrumentation.Visual observations; use of senses (i.e.smell); inspection of control measuresimplemented and effectiveness; and, PPE.
WORKPLACE MONITORING - QUANTITATIVE EVALUATIONDocument exposure levels either bymeasurement or use of semi-quantitativemethods. Strategy developed depends onthe reason for evaluation. Purpose isFIRST!Sampling objectives: EITHER engineeringtesting, surveillance, or control; ORcompliance, health research, orepidemiological purposes.
STRESSOR IDENTIFICATION/CONCENTRATION ESTIMATIONHazard information by familiarization andthen prioritization (probability/consequenceof overexposure) based on significance formonitoring.Probable range of contaminantconcentrations to assist with samplingstrategy development and facilitateselection of monitoring methods and/orspecific equipment for assessment.
SAMPLING AND ANALYTICAL METHOD SELECTIONUse of accurate, sensitive, specific, andreproducible analytical methods and propercalibrated sampling equipment. Knowledgeof interferences and detection limits.Principles – validated methods (OSHA,NIOSH).Specificity, selectivity, and otherconsiderations for direct-reading instruments.Limitations - combine workplaceobservations with measurements for resultinterpretation.
EQUIPMENT DECISIONS Type of analysis or information required Efficiency of the instrument Reliability of the instrument under various field use conditions Exposure assessment for medical and epidemiological studies Portability and ease of instrument use Personal choice of IH based on past experience and other factors
EQUIPMENT SELECTION Calibration – necessary to insure data representative of field exposures; results based on accuracy of instruments (i.e. direct-reading) and/or sampling and analytical methods; pre- and post-calibration to determine air sample volume; temperature/pressure adjustments IH use of proper PPE during field assessments
SAMPLING STRATEGYOverall plan or framework for sampling thatmay include the type and number ofsamples to be collected; the methods to beused, and their accuracy, and the objectivesfor monitoring.Decision made with confidence andminimum cost and effort.Complicated by numerous variables.
SAMPLNG STRATEGY WHAT and WHY? Where to sample? When to sample? How long to sample? Whom to sample? How many samples to collect? How should the samples be obtained?
WHERE??? Personal or area Breathing zone Location(s) are dictated by Need Source of contaminants by Area
WHEN??? Determined by information required Type of operation assessed Multiple shifts Geographic/climatologic conditions
HOW LONG??? Minimum time is usually determined by the time interval necessary to obtain a sufficient amount of the contaminant on the sample media for laboratory analysis. Sensitivity of analytical procedure Dependent on contamination concentration Full work shift for compliance Work tasks; partial periods; multiple samples to measure entire work shift
WHOM??? Depends on purpose of monitoring. For compliance, then sample maximum risk employees with highest exposures. Random sample of employee by exposure group for a comprehensive assessment
HOW MANY??? Dependent on the purpose of workplace monitoring. For comprehensive assessment, a minimum of six samples for each exposure group may be needed for a decision of acceptability. With time and budget constraints, semi- quantitative methods may be used. No set rule! Use personal experience to collect optimal sample number given budgetary constraints.
HOW??? Instrument choice depends on: - Portability and ease of use - Efficiency and analytical method - Reliability under various conditions of field use - Type of analysis or information required The choice of instrumentation and testing and analytical procedures is ultimately dependent on the capabilities of the analytical laboratory.
SAMPLE COLLECTION Follow strategy so as not to bias results or compromise the integrity of the conclusions. Adjustments or modifications as needed Phased sampling strategy as an option Understand procedures; equipment/supplies Understand impact on the work environment Recordkeeping – extensive notes and INFO
SAMPLING AND ANALYTICAL PROCEDURESSelection of measurement method dependson sampling strategy requirements andpurpose of workplace monitoring based on: – duration of sampling [TWA vs. STEL], – sensitivity of the method/detection limit, – freedom from interferences/result bias, – time to reporting of results, – accuracy.
INTERPRETATION OF SAMPLING RESULTS Concentrations Calculations based on time periods Test statistics Professional judgment – acute/chronic Information for data interpretation - Precise nature of material/agent - Intensity/magnitude of exposure - Reliable knowledge of frequency/duration
COMPARISONS TWAs vs. STELS Best sampling strategy for full shift integrated personal sampling; short-term tasks add more variability [peak/ceiling - instantaneous]; general area samples are not specifically recommended. OELs – direct result comparison with OSHA PELs, ACGIH TLVs, NIOSH RELs, AIHA WEELs, etc.