Assessing and managing workplace exposure to chemicals

The 17th century Italian physician Ramazzini invited doctors to extend their interrogatory questions of their patients to include “What is your occupation?” This invitation is still relevant today.

Many people present to their General Practitioner concerned about the possible health consequences of chemical exposures. Despite this, the health effects of the commonest workplace chemical exposures are often overlooked.

Assessment of patients with such exposures, and their clinical outcomes, is complex and difficult, with many cases presenting as more conventional illnesses. Failure to recognise a problematic exposure, coupled with on-going exposure, can lead to medical conditions that are difficult to manage.

Effective evaluation of possible chemical exposures contributing to a health concern requires consideration of a person’s occupation as part of their clinical history, as well as some knowledge about the effects of specific chemical exposures.

The potential medical consequences of workplace chemical exposures

Workplace chemical exposures can result in the development of a new medical condition, however, the more common consequence is a worsening of a pre-existing condition. For example, a welder who has asthma may develop more brittle asthma as a result of exposure to welding fume.

The impact of adverse workplace exposures on a person with compromised health is often under-recognised. In such situations, the workplace exposure initiates the “illness cascade”. For example, a worker who is obese, with poorly controlled diabetes, who smokes, and who works in an enclosed environment with petrol/ diesel powered equipment without adequate ventilation (carbon monoxide exposure), is suddenly required to undertake some excess physical activity (emergency response); this can lead to angina or collapse.

Assessing a patient’s concerns

In order to detect health consequences from any exposure of concern, it is necessary to identify which substances are involved, and understand the likely effects of these chemicals. Patients who present with concerns about hazardous substance exposure without any particular exposure history (or specific substance of concern) are particularly challenging to assess.

Once the substance of concern has been identified, a clinical history should identify the patient’s occupation and in particular what the tasks and likely exposures are. The health consequences of chemical exposures depend not only on the material that people are exposed to but the route of exposure, metabolism and excretion. An important concept is “dose” – how much for how long?

The timing of symptoms is important. Symptoms that persist during an absence from work tend not to be related to the workplace. Ask about chronic effects of the exposure, but also try to identify episodes of acute toxicity around the exposure time. For example, pesticide spray exposures are often blamed for low grade chronic “unwellness” but a history of symptoms, such as acute malaise, skin rashes or shortness of breath, around peak exposure times (e.g. mixing concentrate, unexpected soakings) would suggest a more significant exposure.

Identifying health consequences of chemical exposure is only occasionally aided by specific testing of the patient or the workplace. These measurements are either of:

1. Exposure assessment, e.g. static sampling in a workplace or personal sampling of the worker (e.g. dust/fume measurements in the breathing zone of a welder). There are specific “acceptable” concentration limits for known hazardous chemicals (in New Zealand called Workplace Exposure Standards). However, measurement against these Standards is usually only done by concerned companies.
2. Effect assessment, e.g. peak flow measurements at work or away from work
3. Specific biological monitoring (very occasionally), e.g. blood lead levels

If physiological or laboratory measurements are possible, they might be taken both during and away from exposures.

In reality, there are few exposure assessment services available to General Practitioners, and physiological measurements (“effect assessments”) are usually the only accessible tests in primary care.

There are currently few New Zealand governmental resources to assist General Practitioners with advice on assessment of workplace exposure to chemicals and illness this may cause. Potential sources of information/contacts include:

• The University of Otago Department of Preventive and Social Medicine
• The National Poisons Centre
• Occupational medical specialists
• Local occupational health services
• Medical literature

Other considerations

Many people at work fear that they place their job security at risk if they report their concerns about workplace conditions.

General Practitioners may be involved in a patient’s dispute with their employer or the workplace insurer, e.g. providing a medical certificate. Such circumstances often complicate determining whether a workplace chemical exposure may be affecting their patient’s health, confirming the suspected relationship, and advising on appropriate treatment or protection.

Management of occupational exposure

General Practitioners have two main roles in management of workplace exposure related illness: treating the symptoms, and providing the patient with appropriate information about preventing further exposures. An overall goal is to help the patient to maintain their work.

Many conditions are either self-limiting (the symptoms resolve when exposure ceases or shortly after) or can be attributed to historical exposures. Controlling the exposure at the source (e.g. ventilation, substitution with less toxic products) is optimal because it controls the symptoms and benefits employer and employee. In general, recommending “safety gear” (Personal Protective Equipment) is not a useful way to provide protection.

Where workplace chemical exposures cannot be reduced, or the health consequences of these are significant, advice about seeking suitable alternative work may be necessary. For example, when people develop allergies to workplace chemical exposures, they usually have to abandon that work.

The important message is that control of symptoms caused or worsened by workplace exposures becomes very difficult where the linkage between those symptoms and that exposure remains undetected. Enquire about a patient’s occupation, and consider if workplace exposure to chemicals is causing or contributing to their symptoms.