Conditions for Entitlement – Occupational Diseases Policy 21-111 | Effective Date: January 17, 2019

Purpose

The purpose of this policy is to outline how WorkSafeNB gathers and weighs medical evidence during the adjudication of occupational disease claims. 

Scope

This policy applies to all claims for compensation involving occupational diseases.

Statements

1.0 General Statements

WorkSafeNB uses Section 7 of the Workers’ Compensation Act (WC Act) and Policy 21-100 Conditions for Entitlement – General Principles to adjudicate all claims for compensation involving a personal injury caused by accident arising out of and in the course of employment, including claims for occupational diseases.

The WC Act defines an accident as a: 

• Wilful and intentional act not being the act of the worker who suffers the accident;
• Chance event or incident occasioned by a physical or natural cause;
• Disablement caused by an occupational disease;
• Disablement or disabling condition; or
• Disablement from mental stress that is caused by an acute reaction to a traumatic event.

Occupational diseases are illnesses that an injured worker may develop as a result of certain exposures, and are peculiar to or characteristic of a particular industrial process, trade or occupation. Occupational diseases or related disablements may have occurred over time, and may have resulted from an exposure with one employer or from multiple exposures at various workplaces. Regulation 84-66 outlines some diseases that are known to be work-related, however these diseases are not exempt from WorkSafeNB’s adjudication process to determine if the disease arose out of and in the course of employment.

In order to accept a claim for compensation, WorkSafeNB must determine that the disease is an occupational disease that arose out of and in the course of employment. To determine this, WorkSafeNB:

• Evaluates scientific and medical literature to determine that there is a probable causal association between the exposure reported and the disease (section 2.1); and
• Weighs other information, such as medical evidence specific to the claim, to evaluate if the particular exposure and the disease reported are work-related (section 2.2).

2.0 Medical and Scientific Evidence of Causation

WorkSafeNB considers medical evidence to be the most important factor for establishing if a work-related exposure could have caused the disease. When evaluating medical information, WorkSafeNB uses a method that is:

• Evidence-based;
• Reproducible; and
• Transparent.

This means that WorkSafeNB’s evaluation of medical information and the resulting conclusions:

• Are based upon the most credible scientific literature and studies;
• Can be accurately reproduced by other health care providers; and
• Are easily understood.

For more information on the types of medical and scientific literature WorkSafeNB accepts, see Policy 25-014 Medical Aid Decisions.

To determine any causal association between an exposure and a disease, WorkSafeNB gathers and weighs evidence to answer the following two questions:

1. Does medical and scientific literature show that the diagnosed medical condition is characteristic of the occupation?
2. If yes, does all available evidence establish that the disease in this claim arose out of and in the course of employment?

2.1 Determining Association Between the Exposure and the Disease

WorkSafeNB applies the Bradford Hill criteria to its analysis of medical and scientific literature to determine any causal association between the exposure and the disease. The Bradford Hill criteria is a tool that was developed to interpret epidemiological evidence of a general causal relationship between exposure to an agent and the disease. Specifically, WorkSafeNB uses this criteria to determine:

• Plausibility – is there a biologically plausible relationship between the proposed exposure and the condition?
• Temporal – did the condition occur after a reasonable duration of exposure and latency based on current medical/scientific knowledge?
• Specificity – is the condition being linked to a specific type of exposure as opposed to multiple vague exposures?
• Dose-response – does the exposure exhibit a dose-response gradient in which little exposure gives rise to a mild or sub-clinical condition and heavy exposure to a more severe, overt condition?
• Consistency – is there a consistency across the literature on the relationship between the proposed exposure and the condition?
• Strength of association – the relative incidence of the condition under study between those exposed and those non-exposed.

If the criteria supports a causal association between the exposure and the disease, then WorkSafeNB determines the strength of association in terms of the Attributable Risk Fraction.

An Attributable Risk Fraction of:

• Fifty percent or greater means it is more probable than not that a case of the disease is attributable to the specified agent, exposure, or occupation;
• Between twenty-five and forty-nine percent means a case of the disease could be attributable to the specified agent, exposure, or occupation; but an alternate cause is more likely; or
• Less than twenty-five percent means it is unlikely that a case of the disease is attributable to the specified agent, exposure or occupation.

2.2 Determining If the Specific Exposure Caused the Disease

After WorkSafeNB has analyzed the medical and scientific literature and is satisfied that there is a probable causal association between the exposure and the disease, WorkSafeNB then proceeds to confirm if the:

• Worker was exposed to the substance that was reported to have caused the disease;
• Exposure occurred at work; and
• Exposure caused the disease.

At this stage, WorkSafeNB examines the specific facts and information of the claim to determine if it is reasonable that the worker’s disease arose out of and in the course of employment, including:

• Where the exposure occurred;
• Type, nature, duration, and frequency of exposure;
• Latency period specific to that disease;
• Specificity of exposure;
• Whether or not personal protective equipment was used;
• Confirmation or diagnosis of the disease;
• The worker’s medical history;
• Specialists’ reports;
• Pathology reports; and
• Evidence of alternate causes.

WorkSafeNB analyzes all information related to the claim in order to make a decision. When the preponderance of evidence weighs more heavily toward the disease being work-related, WorkSafeNB accepts the claim.

For more information on the process used to adjudicate claims, see Policy 21-100 Conditions for Entitlement – General Principles.

3.0 Determining the Date of Accident

Date of accident for hearing loss is determined using Policy 21-112 Occupational Hearing Loss.

For other occupation diseases, other than occupational hearing loss, the date of accident is the date when disablement as a result of the occupational disease first occurred. When there is no evidence of disablement, WorkSafeNB uses the date of diagnosis as the date of accident.