Medical surveillance

June 28, 2002
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Medical surveillance - sounds ominous, but it's a critical safety tool used to detect early signs of work-related illness. In general industry, it's used as a backup to an industrial hygiene assessment. This systematic collection and analysis of data can lead to early detection and sometimes even predict an unidentified exposure.

In addition to early detection, sometimes additional disease and injury risk factors come to light during surveillance. As an added benefit, an intervention may detect a non-work-related disease and promote opportunities for increasing workplace health.

Information gathering

A medical surveillance program begins whenever exposures exceed a chemical's action level, or, if new materials or processes are introduced that raise safety concerns. Proactive safety pros know it's best to study before a potential hazard requires intervention. For some hazards, OSHA requires annual medical surveillance.

To start a medical surveillance you'll get an employee's history, provide a physical examination, do testing and generate an analysis of results. Results are kept confidential so the employee's job isn't at risk, and full documentation is maintained.

As a result of information gathering, you'll do a needs assessment, selecting a target population and proper tests. Test interpretation leads to needed intervention and communication.

Needs assessment - Is the medical surveillance mandated by a regulation? If so, you will find guidance and perhaps letters of interpretation at the OSHA Web site, www.osha.gov.

Basics of a needs assessment are analysis of the potential for exposure, review of material toxicity, guidelines from OSHA, ACGIH and NIOSH to decide whether medical surveillance is needed and the frequency of testing.

Your target population includes current employees who are potentially exposed. A proactive manager should consider adding new employees and new potential hazards to the surveillance before being mandated to do so.

Proper tests - Will you need lab tests on blood and urine? Chest x-rays? Lung function testing? Hearing tests? All these decisions are based on the type of exposure.

In some cases continuous biological monitoring will be required. You will need tests of biological specimens for the presence of the toxin. This monitoring assesses the exposure but may not reveal a disease. While certain heavy metals stay in the blood and urine for a long time, solvents have a short half-life and may not be detectable. For instance, if the solvent exposure occurred on Friday and the employee is tested on Monday, you may not be able to detect the exposure. It tempts the question, "If it goes away, why worry?" Well, the answer is long-term illness and injury.

Protocol - You'll need a protocol for using and interpreting test results. Do you refer this to a primary physician? Is it necessary to remove tested employees from further exposure? What do you do about false positives and false negatives? When will further testing be required? Answers to these questions shape your protocol.

Time to intervene

When test analysis is complete, it's time to intervene. While you're working on intervention you may need to remove the employee from exposure. See if the process or materials can be changed. What about environmental controls? Would ventilation help? Is there a heat or noise hazard that could be reduced?

Finally when you've studied all the engineering control possibilities, you require personal protective equipment. PPE is considered the last line of defense because it relies on employee cooperation and following administrative procedures.

During the communication phase, build empowerment into the new system. Employees are empowered to follow new procedures when they see reasonable, prudent and verifiable guidelines. People accept responsibility and accountability when offered the opportunity to make decisions about their jobs.

Finally, how do you inform the supervisor? Remember that some confidential employee information must not be shared, but respect the supervisor's need to participate and enforce any changes you recommend. Supervisors must reinforce change through example and attitude to support an image of the way the organization responds to health and safety matters.

Knowing the exposures

Let's look at some well-known exposures.

Lead - Present in paint, glazes and stained glass, lead can affect the central nervous system, kidneys, peripheral nerves, blood and reproduction. Some indications are anemia, the wrist drop showing nerves are affected, exposure over the action level and employee history. OSHA's lead standard indicates that a level over 40 ug/100ml is significant overexposure, and worker removal is called for at a blood level of 60 ug.

Mercury - Used as a pesticide, pigment or preservative, mercury can cause central nervous system, behavioral and renal effects. Again, a history, physical examination and urine testing are called for when mercury exposure is suspected.

Arsenic - This can be used in pesticides and affects skin, liver and nervous system. Arsenic is a risk factor for lung cancer. A suspected exposure requires a medical history, physical examination and urine test. Take into consideration that seafood consumption may result in elevated arsenic levels. Arsenic, a heavy metal, stays in the body a long time.

Solvents - Used to clean parts and thin paints, solvents affect the skin, liver, blood, peripheral and central nervous system. Again, a history and physical examination are required as well as a urine test for metabolites. Carbon monoxide in exhaled air or carbonxyhemogloben in blood may show methylene chloride exposure. Solvents are volatile and, therefore, don't stay in the body a long time. They do show up in liver function tests and neuro-system cognitive differences.

Asbestos - Found in plaster, fire retardents and taxidermy, asbestos can cause pulmonary fibrosis and result in lung cancer. The OSHA asbestos standard requires an annual physical examination and a termination examination if the exposed employee leaves the company. An employee history, physical examination, pulmonary function study and periodic chest x-rays are required.

Early recognition

In addition to specific regulatory requirements, OSHA's General Duty Clause requires a workplace free of recognized hazards likely to cause death or serious physical harm to employees. Medical surveillance can help protect your employees through early recognition and treatment. Biological monitoring can also assess potential exposures before anyone works at risk.

Editor's note: This article is based on a presentation given at a museum safety meeting on medical surveillance by Katherine Duvall, MD, MPH, MS, co-director of the Health in the Arts Program, University of Illinois at Chicago, Dept. of Occupational Medicine. Dr. Duvall is the author of "Occupational Medicine State of the Art Reviews: Medical Surveillance in the Workplace," Editor David Rempel MD MPH, Vol. 5, No. 3, July-Sept. 1990, Hanley & Belfus, Inc., Philadelphia.

SIDEBAR: Keeping protocol

In designing your medical surveillance protocol, include:

  • The purpose of medical surveillance and any particular focus on a organ system
  • The type of examination; history items to be included
  • A schedule of surveillance
  • Types of tests to obtain
  • Acceptable test result levels
  • How employees will be notified
  • Follow-up studies
  • Recordkeeping

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