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Accident Prevention Manual for Business & Industry: Engineering & Technology 13th edition National Safety Council. Compiled by Dr. S.D. Allen Iske, Associate Professor University of Central Missouri. CHAPTER 9. OCCUPATIONAL MEDICAL SURVEILLANCE. What is Occupational Surveillance?.
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Accident Prevention Manual for Business & Industry: Engineering & Technology 13th edition National Safety Council Compiled by Dr. S.D. Allen Iske, Associate Professor University of Central Missouri
CHAPTER 9 OCCUPATIONAL MEDICAL SURVEILLANCE
What is Occupational Surveillance? • Epidemiological surveillance is the systematic collection and analysis of health data for planning, implementing, and evaluating public health programs • The ultimate goal of surveillance is prevention of illness or injury. • Focus is on monitoring the health of working populations and the exposure to hazards in the workplace.
The Four Components of an Occupational Surveillance System • Gathering information on adverse health events and exposure circumstances • Distill and analyze the data • Disseminating data to interested parties • Intervening on the basis of the evidence provided by the data to alter the factors that produced the hazards and adverse health outcomes
Occupational Surveillance • How can occupational surveillance be applied? • Working populations as well as individuals workers • Federal, state, and local officials may use the results to monitor and set policy to mitigate workplace risk. • In individual workplaces, employers may use surveillance to establish and monitor prevention programs specific to processes and conditions.
Combined Effects of Exposure • OSHA has medical screening requirements for certain chemical exposures and working populations. • Hazardous waste workers, noise-exposed workers, those who wear respiratory protection • Healthcare professionals generally consider the effects of a chemical independently, but exposure to a single chemical rarely occurs. • Many chemical exposures occur as part of a hazardous mixture. • As chemicals or substances combine in the body the potential for injury or disease increases significantly.
Combined Effects of Exposure (Cont.) • OSHA permissible exposure levels (PELs) and ACGIH threshold limit values (TLVs) were developed under the assumption that workers are exposed to one chemical at a time. • To determine overexposure for a mixture: • Add concentrations of substances as a fraction of their respective TLV • If the total exceeds one, an overexposure has been detected • This is known as the mixture rule published by ACGIH. • The underlying assumption is that “combined” chemicals act on the same end-organ.
Combined Effects of Exposure (Cont.) Example: If an employee is exposed to air that contains 400 ppm of acetone (TLV, 750 ppm), 150 ppm of sec-butyl acetate (TLV 200 ppm) and 100 ppm of methyl ethyl ketone (TLV 200 ppm) during an 8-hour workday, has the exposure exceeded the threshold limit? The formula for additive effects is: C1 + C2 + C3 + … = 1 T1 + T2 + T3 +… Where C = the observed atmospheric concentration, and T = the corresponding TLV. If the sum of the fractions is greater than 1, then the TLV has been exceeded. 400 + 150 + 100 = 0.53 + 0.75 + 0.5 = 1.78 750 200 200
Surveillance of Working Populations • Data collection systems for occupational surveillance: • What illness and injuries are occurring (occupational sentinels) • Why they are occurring (workplace conditions) • How they are occurring (mechanism of injury) • Where they are occurring (industry type, economic sector, establishment size) • When they are occurring (day of the week, time of day, seasonal variations, changes over time)
What: Occupational Sentinel Health Events • An occupational sentinel health event is a disease, disability, or untimely death which is occupationally related and whose occurrence may: • provide the impetus for epidemiologic or industrial hygiene studies • serve as a warning signal that materials substitution, engineering control, personal protection, or medical care may be required • It is useful for managers, healthcare workers, and public health personnel to review health data for individuals or populations to look for patterns that may be related to occupational exposure.
Why/How: Occupational Sentinel Exposures • Hazard surveillance and remediation is a more effective approach to prevention of illness and injury. • Characterization of chemical, physical, biological, biomechanical, and psychosocial hazards associated with work is essential to protect workers from harm. • Hazards may be evaluated on an industry-wide scale or in an individual company. • In addition to exposure hazards that lead to illness, injury mechanisms may be coded in certain health surveillance systems to that mechanisms and circumstances of injury may be determined.
Where: Economic Sector, Industry Type, Job Titles • The Standard Industrial Classification (SIC) codes are used in most workers’ compensation reporting systems. • The North American Industrial Classification System is being used more frequently today. • It breaks down industry and job tasks more finely. • Gives a clearer picture of the work tasks leading to injury.
When: Day, Date, Time of Injury • Systems that record information on when an injury occurred may give clues to reasons for certain types of injuries and provide a focus for preventive activities. • Example: Outdoor construction and agricultural work take place during warmer seasons, and injuries in those sectors are more likely to occur in the summer. • The time of day that injuries occur can give clues about the impact of shiftwork on workplace health and safety.
Types of Surveillance Systems • Active—An agency selects a sample of workplaces, surveys the workplaces, analyzes the data, and extrapolates the results to the U.S. industry as a whole. • OSHA 300 logs and National Health Interview Survey • Passive—Data that are collected for purposes other than occupational surveillance may be used to inform understanding of occupational illness and injury. • Clinics and hospital records, emergency room visits, and workers’ compensation reports
Occupational Medical Screening • Screening—performance of medical testing for the purpose of detecting organ dysfunction or disease before an employee would seek medical care • The main goal of screening is to benefit the individual worker. • May provide surveillance information on populations and identify sentinel cases • OSHA has screening requirements for employees exposed to specific hazards. • Medical screening programs require a systematic approach to data collection and require an understanding of many disciplines in order to be accurate informative and preventive.
Occupational Medical Screening • Prevention • Optimally, the workplace should be monitored for hazardous conditions on an ongoing basis. • Industrial hygiene hierarchy of controls • It is most effective to implement engineering controls or substitute hazardous agents with less hazardous agents. • Removing hazards before exposure occurs is an example of primary prevention. • Medical surveillance can be used for primary prevention if it entails detecting hazardous agents in the tissues of workers before irreversible clinical effects occur. • Example: An employee exposed to lead has elevated blood levels, but he is removed from work before he becomes ill.
Occupational Medical Screening (Cont.) • Prevention (cont.) • Clinical testing may be done for secondary prevention as well: • Example: Workers exposed to solvents, detection of abnormal elevations in liver enzymes in the blood stream, signaling adverse effect of solvents on the liver • Tertiary prevention is undertaken when an irreversible injury or illness has occurred • Goal is to limit damage • Example: An individual who developed asthma as a result of an occupational exposure can be removed from the exposure and treated to prevent exacerbations and limit disease progression.
Occupational Medical Screening (Cont.) • Biomarkers • Biological markers are substances, structures, or processes than can be measured in human tissues that may predict disease. • Biomarkers of exposuremeasure internal dose. • Blood lead level is one of more than 100 such laboratory tests. • Biomarkers may also be used to determine susceptibility to disease. • DNA tests, immunological response, or specific gene sequences associated with certain diseases
Occupational Medical Screening (Cont.) • Biological monitoring limitations • difficulty correlating a health risk with exposure once the exposure information is known • short biological half-lives of some substances • ineffective monitoring for surface active agents • interference of tobacco, alcohol, and other agents with some test results • measurement that may reflect multiple exposure sources (air, food, water, soil, and skin contact), preventing accurate determination of occupational exposure
Occupational Medical Screening (Cont.) • Ethical and legal issues • Markers of susceptibility involving genetic screening in the worksite provoked serious debate over who has a right to the information and for what purpose. • Concerns: potential for discrimination against workers on the basis of racial or cultural characteristics and acquired or inherited genetic susceptibility • Central legal issues address the rights of those monitored and the use of monitoring as a primary control strategy. • Before companies approve the use of biomarkers in health surveillance, they must carefully consider how they will handle and communicate personal health data beyond the physician-patient relationship. • Occupational medical surveillance raises difficult issues related to labor-management relations, labor law, and discrimination.
Medical Screening Programs • 13 steps to design and conduct a screening program • Assess the hazards: evaluate routes of absorption and exposure levels, quantitatively or qualitatively • Identify target organ toxicity: review toxicology literature • Select tests: those which detect disease at an early stage to limit or prevent disease/injury • Develop action criteria: plan for how to interpret data and act on results • Standardize the testing process: a quality-control protocol and standardization of testing to ensure reliability and comparability • Perform the test: informed consent should be obtained from workers and results kept confidential • Interpret the results: utilize predetermined action criteria
Medical Screening Programs (Cont.) • Confirm results: abnormal tests should be confirmed by performing a second test before rendering a decision about removal from work. • Determine work fitness: appropriate tests should be used before recommending removal from the job; retention of salary and benefits may be of concern • Notify workers: notification of results of screening tests should be delivered to the worker promptly and in strict confidence, with an interpretation by a health professional • Diagnostic evaluation: abnormal results should result in a sound, medical evaluation • Evaluate and control exposure: if an occupational health sentinel is detected, the work environment should be evaluated and hazardous exposures controlled • Record keeping: medical records should contain all testing results, interpretation, and copies of employee/employer notification