Health surveillance is an important part of occupational health (OH) practice. It is defined by the Health and Safety Executive (HSE) as being about implementing systematic, regular and appropriate procedures to detect early signs of work-related ill health among staff exposed to certain risks.
Health surveillance may take many forms, from simple self-assessment or a responsible person making basic checks for signs of disease, to periodic clinical and/or physiological assessments of individuals by specialist OH professionals that involve certain screening procedures.
The decision as to who requires surveillance must be evidence-based according to the nature of the hazard and risk. However, responsibility for implementing safety policies rests with managers and safety officers. It is not the OH department that needs to identify which of the workers require health surveillance, although OH professionals should provide guidance on policies and procedures.
Types of health surveillance
In a practical sense, health surveillance can be divided into planned and ad hoc.
Planned surveillance will vary according to the hazard and risk, and to any statutory imperatives.
Ad hoc surveillance is required when:
- staff under regular surveillance are aware of possible symptoms of concern and report them to their manager or OH specialist
- employers independently become aware of symptoms of concern, either through an individual’s reports or medical certification, and should refer the worker to an OH adviser for assessment
- potential risk/exposure situations change, or an abnormal exposure to a respective hazard occurs. Then OH should be informed.
Complying with legislation
Respiratory surveillance must comply with statutory requirements. In the UK, the main applicable regulation is the Control of Substances Hazardous to Health Regulations 2002 (COSHH). The HSE guidance on this legislation says that an initial eight-step workplace risk assessment must be undertaken. From this, health surveillance procedures can be instigated when an employee is exposed to certain listed substances, or has a known adverse reaction to specific substances.
First, employers must determine the nature of the work, and identify whether an individual might be exposed to a hazard, and then assess the duration of potential exposure. They must be in a position to determine and implement reasonably practicable control measures for substances hazardous to health. These are:
- Implementation of health and safety management systems
- Risk assessments
- Prevention and control of exposure
- Maintenance, examination and testing of controls
- Information, instruction and training
- Health surveillance (if necessary).
Awareness
Before providing respiratory health surveillance to individuals, the individual should be made aware of the reason for and nature of the surveillance. They should also be aware that a statutory health record will be kept for 40 years, that they can have access to that record under the Data Protection Act 1998 , and that feedback will be provided both to themselves and their employers should the results indicate a requirement for further assessment of them or their work. In turn, this may involve modifications to their environment or their job. Properly informed staff must then either comply with this legal requirement or cease working in that environment.
Allergens
The specific concern of respiratory health surveillance is the early detection of adverse reactions to respiratory allergens. Work involving animal handling is known to cause occupational asthma in certain circumstances. This is caused by animal allergens which comprise high molecular weight proteins that are located in animal tissue and serum or in insect carapaces/wings. However, they can also be found in sources external to the animal, such as urine, fur, saliva, and faeces, or in contaminated products, such as bedding materials.
Factors influencing the risk of sensitisation include the species, the route of exposure, the level of exposure, the duration of exposure and personal susceptibility. An individual’s response can vary greatly according to the type of animal.
Generally, large mammals (sheep, cows, pigs, goats, horses, dogs and primates) present a very low risk. Sensitisation to amphibian or fish protein from skin exposure alone is rare and skin irritation can be prevented by using gloves where allowed (ie, when they do not hurt the animal). Reptiles do not normally present a hazard.
In the UK, the reported incidence of occupational asthma and rhinitis is greatest among those working with small mammals (including mice, rats, guinea pigs, hamsters, cats, rabbits and ferrets) and insects. The species most frequently used in research at the university are mice and rats. When considering the need for respiratory health surveillance, it is useful to consider whether an individual will be exposed to more than one species (in such cases, the highest-risk species usually take precedence). Once sensitised, an individual remains so for life.
In assessing the risk of exposure to aeroallergens and the need for health surveillance, the wearing and effectiveness of personal protective equipment and respiratory protective equipment is generally not taken into account (with the exception of the carefully assessed use of powered respirators). Consideration should also be given to individuals who could be exposed to aeroallergens despite not actually working directly with animals (eg, clerical staff within animal facilities).
The risk of sensitisation, and the development of symptoms of occupational asthma, increases with the duration of exposure. The time-course for such events and the influence of individual environmental factors still requires much investigation, but most workers who develop LAA do so within the first three years of exposure.
As a generalisation, the average period between the first exposure and the development of symptoms is shortest for nasal symptoms and longest for respiratory symptoms. However, there is great variation within this. For individuals with a personal or strong family history of atopy (eg, asthma and eczema), the risk of developing occupational asthma occurs at lower levels of duration and intensity of exposure to allergens. A history of atopy may help determine the level of surveillance for an individual (eg, enhanced for a moderately severe asthmatic). This becomes important, for example, if a decision needs to be taken about whether to redeploy an exposed worker who has reported symptoms.
Work-related asthma
When there is an association between symptoms and/or signs of variable airway airflow limitations and/or airway hyper-responsiveness and work, then the asthma can be regarded as ‘work-related’. This type of asthma should be distinguished from pre-existing conditions, since the implications to the worker and the management of the disease differs.
Work-related asthma includes two distinct categories:
Work-aggravated asthma – pre-existing or coincidental new onset adult asthma, which is made worse by non-specific factors in the workplace
Occupational asthma – adult asthma caused by workplace exposure, and not by factors outside the workplace. Occupational asthma can occur in workers with or without prior asthma.
Periodic respiratory health surveillance for occupational asthma aims to identify sensitised workers or cases of asthma at an early and reversible stage of the disease. Methods commonly used in surveillance to identify cases of occupational asthma are respiratory questionnaires, spirometry (to measure forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) and, where appropriate, identification of a specific protein by skin-prick test or serology.
Communication opportunity
Notwithstanding some of the problems with questionnaires, there is no significant evidence that spirometry detects cases of occupational asthma that would not be detected by a respiratory questionnaire. Spirometry may also identify false positives due to poor effort during the testing, and also may not identify additional cases of asthma. However, it is arguable that spirometry does allow an opportunity for better communication with an OH professional.
Assuming all other controls are in place, no individual should be potentially exposed to allergens as part of their work without an appropriate referral from their employer, an OH baseline assessment and consideration for low- or high-level health surveillance. The initial assessment should be based on information gained from questionnaires resulting from referrals from employers at the time of pre-employment, redeployment or pre-placement.
The animals or substances to which it is known a potential employee may be exposed must be identified by the employer at this time. Where pre-employment/pre-placement assessment indicates a known sensitivity, or highly likely sensitivity, to an animal or substance, then the OH practitioner must recommend that the individual is not exposed to that work.
Some individuals with non-respiratory health problems, such as severe heart disease, may also be cautioned against working in some areas. This is not because they are more likely to develop asthma, but because if they did, the consequences for them could may be greater than for a ‘fit’ individual.
Some individuals are cross-allergenic and, if allergic individuals are employed in the low-level handling of animals or substances to which they have no known allergy, a higher level of surveillance may still be prudent. Similarly, individuals with severe atopy or asthma may benefit from higher levels of surveillance, at least in the first 12 months of employment. Where staff may be exposed to allergens from more than one source, then exposure to the highest-risk source should take precedence when determining health surveillance requirements.
An individual’s requirements for health surveillance should be reviewed if exposure circumstances change, and should be reassessed annually, if not more often.
Finally, should an informed individual identified as requiring only low-level health surveillance ask for a higher level of surveillance, the individual’s request should normally be granted.
It would be appropriate to categorise the requirement for ongoing health surveillance into low- and high-level, where low-level is divided into ‘baseline only’ and ‘standard’, while high-level health surveillance is called ‘enhanced’ (see box).
Results of surveillance
After each planned episode, a verbal report should be given to the individual. The health record should be created or updated, and a report should be provided to the referring manager/employer. Where possible, grouped data to help monitor the effectiveness of controls should also be provided.
Ad hoc surveillance results should initially be dealt with in the same manner as standard self-referrals and management referrals to the OH service. However, in addition to clinical considerations, results may have implications for hazard control and personnel management.
Indicated health issues
Where surveillance indicates the need for further assessment, this should be undertaken on a case-by-case basis. In the first instance, the employee and the employer should be notified verbally and in writing. At this stage, it should be established, as far as possible, that symptoms or signs are indeed work-related.
For the individual, the initial priority is to keep people at work wherever reasonable. However, to reduce the risk of exacerbating the problem, they should not return to an environment where the same exposure to allergens exists. The employer will need to review exposure controls and there will need to be regular reviews of the situation. If symptoms cannot be controlled and/or eliminated, then redeployment or termination of employment of the worker will need to be considered as a last resort.
Robert Dunn is senior occupational health adviser at the University of Oxford
Respiratory health surveillance requirements
Low-level surveillance required
When some workplace exposure to allergens will occur, but the exposure will be less than significant (see standard health surveillance, below), and where individuals might otherwise be enrolled into standard or high-level surveillance, but will be at risk for less than six cumulative weeks.
- Baseline only
Standard surveillance required
Where significant exposure is for less than 15 hours per week. ‘Significant exposure’ could be defined as where a staff member is required to work with animals or substances for at least three hours in a day, at least one day a week, for at least two months.
- A baseline assessment by verbal questionnaire and lung function test
- Then a written questionnaire surveillance after six, 12 and 52 weeks.
- Annual surveillance thereafter.
High-level surveillance required
Where there is exposure to animals or substances for equal to or greater than 15 hours per week, or where exposure to allergens is judged to be particularly intense, then a shorter time than 15 hours should be set. Staff who have been in a low-level surveillance programme, and who develop symptoms consistent with allergy or asthma may be put on a high-level health surveillance programme (unless it is recommended that they no longer work where exposure is possible).
- A baseline assessment by verbal questionnaire plus lung function test
- Then an interview assessment and lung function test at six, 12 and 52 weeks
- Thereafter, an interview assessment and lung function test is to be undertaken annually.
