Year : 2018  |  Volume : 22  |  Issue : 3  |  Page : 117--120

Occupational health surveillance

Damodar Vishnu Lele 
 Occupational Health Physician (Retired), Hindustan Lever Ltd. Bombay Factory, Sewri, Mumbai, Maharashtra, India

Correspondence Address:
Damodar Vishnu Lele
202, Arkade Adornia (Bhagirath Condominium) Plt. No.8, Pahadi School Road No.2, Jayprakash Nagar, Goregaon east, Mumbai 400 063, Maharashtra

How to cite this article:
Lele DV. Occupational health surveillance.Indian J Occup Environ Med 2018;22:117-120

How to cite this URL:
Lele DV. Occupational health surveillance. Indian J Occup Environ Med [serial online] 2018 [cited 2019 May 23 ];22:117-120
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Full Text

“Occupational illness” means a condition that results due to an exposure to risk factors such as physical, chemical, or biological agents in a workplace during work activity to the extent that the normal physiological mechanisms are affected, and the health of the worker is thereby impaired. The term “occupational illness” includes occupational diseases as well.[1]

 Missing the Diagnosis

Physicians do not consider occupation or environment as cause of sickness during the process of differential diagnosis. Lack of curiosity about what people are doing and spending half of their waking hours means that possible subtle influences of work on health are commonly missed by doctors, and the perception that work-related ill health is rare is thus reinforced. High degree of informed suspicion is the principal tool for correct diagnosis of occupational disease.

The term “surveillance” is derived from the French word meaning “to watch over.” In public health, surveillance was originally developed as part of efforts to control infectious diseases, but the principles of surveillance can potentially be applied to other problems such as chronic diseases (diabetes, cancer, or high blood pressure), occupational diseases, or social problems (drug addiction). Health surveillance is a public health methodology, which aims to detect undesired health effects in a given population, with the primary aim to eliminate the source of the problem.

Surveillance is an important core activity in the practice of occupational health. Two broad groups of surveillance are commonly performed – hazard surveillance and health surveillance. Although the focus of the former is hazards at the workplace, the latter type of surveillance pertains to the health of a person from a particular group of workers. Both have important roles in occupational health practice and are complementary.[2],[3],[4]

Surveillance data reveal trends or emerging patterns in workplace hazards and illnesses. To be effective, surveillance has to be followed by preventive corrective action and by evaluation of the effectiveness of intervention.

According to the definition of the International Labor Office at page 22, “Occupational health surveillance is the ongoing systematic collection, analysis, interpretation, and dissemination of data for the purpose of prevention.” It is designed to detect potential workplace hazards before irreversible health effects occur and provide information on where, how, and why workers get sick or hurt on the job.

In contrast to surveillance of the working environment, which examines hazards/factors in the working environment, workers' health surveillance gathers health-related data of and from workers in order to identify and tackle harmful exposures at work. The combination of the two approaches provides the best result to obtain a more accurate picture of the given occupational safety and health situation. The results of health surveillance should be fed into the continuous risk assessment process of the workplace. Similarly, the exposures to hazards identified during risk assessment should guide the scope and measures of health surveillance and screening activities.[3],[5]

 Health Surveillance

A health-surveillance program is composed of a systematic set of procedures that will detect the early signs of work-related health changes that could indicate damage to the individual's well-being. This program may include specific medical surveillance by health professionals which in itself may include clinical examinations or biological/biological effect monitoring to measure and assess both uptake and/or the effects of exposure to certain environments. Health surveillance is an important part of health-risk management and seeks to confirm whether employees are potentially exposed to existing workplace hazards, whether the control measures are effective and the worker is showing no biological or clinical changes that could indicate damaging exposure. Health surveillance needs not be conducted when there is no exposure or reason to expect an exposure unless specifically required by legislation.[6]

 Exposure Monitoring

Exposure monitoring is conducted to evaluate workplace health and safety conditions as they relate to workers' exposures to chemical, physical, and biological hazards during the time they are in the working environment. Monitoring assists management in selecting and implementing effective workplace engineering controls; developing administrative controls; and selecting, using, and determining the limitations of personal protective equipment.[6]

 When is Health Surveillance Needed?

WHO set the principles of screening for public health (including “industrial health examination”) in 1968. These “Wilson and Jungner principles of early disease detection” are still valid today in the following circumstances:[1]

There is an identifiable disease or other identifiable adverse health outcome which may be related to exposureThere are suitable safe/simple/valid tests/techniques for detecting indications of the disease or health effectsThere should be a recognizable latent or early symptomatic stage (detectable preclinical phase)There should be an agreed policy on criteria of diagnosis for occupational disease.

 Statutory Health Surveillance

The Factories Act, 1948 (as amended in 1987), and the rules framed thereunder provide for preemployment and periodical medical examinations of workers employed in industries with hazardous chemicals/processes and dangerous operations under Section 41-C and Section 87, respectively. A list of 29 notifiable diseases in Schedule III, permissible exposure limit (PEL) values in Schedule II, and list of dangerous operations is given in the Factories Act.

Besides conducting occupational health (OH) surveillance, there is also a requirement that records in Form 7 should be maintained for the duration of employment plus 30 years, and access of the employee to his or her personal records should be granted on request.[7],[8]

A well-run medical surveillance program can aid in:

(1) early recognition of a relationship between exposure to a hazard and disease and is an indicator of the effectiveness of existing control measures by detecting any signs of adverse health changes at early stage and boosts health-promotion activities (2) highlighting lapses in workplace control measures.

Collecting data is merely one step. Critical goal is to prevent diseases. Any data collected must be organized and carefully examined to arrive at actionable conclusion.

It is essential that employers have a health surveillance policy, which should state clearly that why the surveillance is required, and what action will be considered in the event of the employee being unable to continue working with a specific hazard.[2],[3],[4]

 Occupational Health Surveillance is not a General Check-Up

Criteria and tests should match occupational risk-exposure profile of employee, tests must be valid, reliable, and geared for the population at risk and should satisfy statutory/legal requirementsThe disease should be identified in its latent stage, not when symptoms appearScreening techniques include questionnaires, physical examinations, and laboratory evaluations such as chest films, pulmonary function studies, audiometric evaluations, and biological monitoringWhere feasible, tests are noninvasive and cost-effectiveTreatment is effective at an early stageFew tests may be added to screen for life style diseases/ non communicable diseases (NCDs)Medical surveillance is a continuing process and not a “one off” project[2],[3],[4]Management relies on information from OH physician and takes prevention-oriented actions based on information received. Surveillance involves taking information in, analyzing, interpreting it, and disseminating it to those who need it. To be effective, surveillance has to be followed by preventive corrective action, counseling, and evaluation of the effectiveness of intervention.[7],[8]

The starting point of any health surveillance is the hazard identification and risk assessment which can include environmental monitoring, hazardous material registries, industrial hygiene, and engineering controls. Hazard identification and risk assessment help to identify specific need for health surveillance. We should not use health surveillance as a substitute for undertaking a risk assessment or for implementing effective controls.

Steps for conducting OH surveillance

Risk assessment – Exposure assessment and risk assessment for target-organ damage; identify hazardous agents, materials, and processes; find out what health risk are; review work processes and toxicity of materials and prepare risk matrix; identify who might be at risk from exposure to those hazards and how; screenable health effects are those that can be detected during the preclinical phase and where intervention at this stage is more beneficial than during later stages of the diseaseSelection of goals and target population – Identification of the group(s) of workers for which surveillance or screening activities will be appropriate; periodic medical examinations at scheduled intervalsChoice of testing modalities – Selection and standardization of test procedures and quality control for each screenable health effect dependent on target organ; do certain workers need special tests?Collection of data and reconfirmation of abnormal results.

Interpretation of data – Predetermined action level criteria:

Intervention: Decide what to do to prevent harm to health; take corrective measures; removal of employees from further exposure or job transfer if warranted; verify effectiveness of action taken by repeating the tests to confirm that hazard/risk is eliminated or reduced to acceptable levelCommunication, education counseling, and further medical evaluation; evaluation of program and of work environment to reduce the exposure to safe levelRecord keeping of the total activity including modifications carried out; continuation of health surveillance after cessation of exposure, especially for conditions with long latency; determination of whether additional or special surveillance should be started after specific events, for example, following a chemical incident like spills where uncontrolled or nonroutine increase in exposure may occurAt times, the extent of exposure required to produce a health effect may not be well defined, as in exposure to sensitizers like enzymes (sensitizing dose and triggering dose) and to carcinogens. The long-term health effects of the specific carcinogens are unclear in some instances. A current example is the health surveillance of soldiers who were exposed for a short period to depleted uranium during their combat operationsThere may be pressure to initiate health surveillance because of concerns related to unique circumstances of exposure, case reports of clusters of disease, or media and political attention apart from legal requirement.[2],[3],[4],[5]

Notification of occupational diseases as an outcome of health surveillance: Most countries require the statutory notification of prescribed occupational diseases.

 The Sentinel Health Event Approach

“Sentinel health event is a case of unnecessary disease, unnecessary disability, or untimely death whose occurrence is a warning signal that the quality of preventive or medical care may need to be improved.” It warns about inadvertent occupational exposures and serves as a warning signal for immediate interventional activities such as material substitution, control at source by engineering modifications, administrative control like relocating a person, compulsory use of personal protective equipment (PPE), etc. Sentinel case event identifies early cases of harmSuch cases trigger interventional activities. Effective health surveillance program warns about imminent problems where prompt investigations averted disastersIn a petrochemical plant, leak of benzene pipeline under the control room was detected during periodic medical examination of workers of plant and of control room. Pre- and postshift examination of urine samples of control room workers revealed more than 50 mg/L urinary phenol indicating significant exposure to benzene when urine samples of plant workers were negative. Ambient monitoring facility was not available[9],[10],[11],[12],[13],[14],[15],[16]In a fast moving consumer goods (FMCG), there were incidences of contact dermatitis on change of pH of chemical, on switching over to indigenous raw material instead of imported materialThere was incidence of exposure to industrial X-rays during thickness testing of tanksIn a multinational, change in denaturant resulted in respiratory symptoms among workers.

 Examples of Health Surveillance

Biological monitoring

For example, 2,5-hexane dione estimation in urine for workers to exposed in methylene chloride, urinary phenol estimations for benzene, estimation of blood levels for lead and arsenic in hair.

Biological effect monitoring

For example, cholinesterase in blood of workers exposed to certain organophosphorus pesticides.

Enquiries, inspection, or exam by a suitably qualified person

For example, an occupational physician or occupational health nurse administering a questionnaire for symptoms of asthma, or for dermatitis.

Medical surveillance

For example, lung function measurement in workers exposed to substances known to cause occupational asthma, chest X-rays in workers exposed to respirable quartz.

 Clinical and Physiological Assessments

Exposed workers with early subclinical changes may need to be removed from further exposure so as to reverse the early changes. Nonoccupational causes also must be considered in case of peripheral neuropathy in a middle-aged worker could result from occupational exposure to n-hexane, alcoholism, and/or diabetes mellitus.

 Molecular Biomarkers as Indicators of Susceptibility

Technological advances in molecular biology over the past two decades have produced sophisticated techniques and development of newer molecular biomarkers for exposure, response, and genetic susceptibility. They include measurements for structural gene damage, gene variation, and gene products in cells and body fluids, for example, oncogenes and tumor suppressor genes, DNA adducts, gene products and genetic polymorphisms, and metabolic phenotypes in exposed populations.[3],[4],[6],[8]


A workplace medical surveillance program needs to be tailored to the specific circumstances of the enterprise.

Health surveillance techniques should be sensitive, specific, easy to perform and interpret, safe and noninvasive, acceptable, relevant, scientifically valid, and effective.

Does the system do what it is supposed to do?How is operation of the system?Who is reporting? To whom? What information is collected? How is information stored? Who analyzes the data? What are the findings? How often are reports disseminated? To whom? Are actions taken as a result of data?Cost.


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