Allergic Sensitization and OELs

[Guest guest]

Speaking of work-related asthma, ALARA vs PELs, EU REACH, allergies not being a significant cause of symptoms, etc., I happened to receive the attached PDF file today from a colleague on another list.

It is a 2008 publication from the He a l t h C o u n c i l o f t h e N e t h e r l a n d s titled,

"Prevention of work-related airway allergies -- Recommended occupational exposure limits and periodic screening"

Sorry for the lost formatting and the attachment (I don't have a link) but here is an excerpt:

"Sensitisation is the best basis for the calculation of toxicology-based OELs. An occupational exposure limit is based on the most ‘critical’ adverse health effect associated with the relevant substance. The critical effect may be the effect that is first observed when exposure increases, or the effect that is most significant in the development of disease.

Where allergic respiratory disorders are concerned, the committee is of the opinion that allergic sensitisation should be regarded as the critical effect. Allergic sensitisation is the best starting point for the calculation of OELs, since it

plays a crucial biological role and is a prerequisite for the development of allergy. Once sensitisation has occurred, continued exposure will lead to allergy in most cases.

An exposure level below which no sensitisation develops can exist Current scientific knowledge regarding the relevant allergic immunological mechanisms leads the committee to believe that it is plausible that a threshold level exists, below which no allergic sensitisation may be expected. This level may be very low: so low, in fact, that little of an allergen is needed to provoke an allergic immune response.

Where a few allergens were concerned, the committee considered whether threshold levels could be deduced from the available epidemiological data. This does appear to be possible where soluble platinum salts are concerned. However,

no evidence of a threshold level was observed for (wheat) flour dust, even at low levels of exposure. More detailed study is needed before conclusions may be drawn regarding other allergens.

Furthermore, the results of animal studies provide a mixed picture. For instance, a threshold level was observed in a few experiments, but in others not. The committee emphasises, however, that the outcomes of the animal experiments

need to be interpreted cautiously, since the experimental exposure conditions tend to differ considerably from workplace exposure conditions. The design of the animal inhalation models could be improved as well. Preferably health-based occupational exposure limit should be derived

Current knowledge suggests that a threshold level does exist for inhaled allergens.

This implies that health-based recommended occupational exposure limits can be calculated for allergens using the same procedures and methods as those used for other non-carcinogenic substances. Hence, the first step towards calculating

such a limit is to determine whether, in the given instance, it is possible to use a method such as the common no-observed-adverse-effect-level method, the benchmark dose method, or another similar statistical model for human data.

However, the committee believes that, where most allergens are concerned, it will not be possible to calculate a reliable health-based recommended occupational exposure limit by any such method. The reason being that, in most cases,

the threshold level will be too low to discern using the techniques presently available.

If that is not possible, a reference value can serve as an alternative

The committee therefore proposes an alternative approach for those allergens for which no reliable health-based recommended OEL can be calculated by the established methods. This approach involves determining reference values, i.e.

concentration levels that correspond to predefined accepted levels of risk of allergic sensitisation.

These reference values can then be used as a basis for assessing occupational exposure limits. The committee recommends that the predefined accepted level of risk should take account of the background prevalence of the allergen in question.

However, the final decision on the predefined accepted level of risk will also depend on policy and social considerations."

Steve Temes

[Guest guest]

Steve:

A few comments

C1: They don't (within the text you provided) do a good job of

explaining prevention of induction versus prevention of elicitation.

Induction is easier to prevent, and better from a health and economic

standpoint (all things equal).

C2: For " The committee recommends that the predefined accepted level of

risk should take account of the background prevalence of the allergen in

question. "

That would tend to indicate using outdoor air as one background basis and

indoor (in a well maintained place) as another basis.

C3: Although I like a lot of the Netherlands' work, for example their

consideration of human data trumping animal data [DECOS, Glutaraldehyde,

Health-based recommended occupational exposure limit, May 2005] the

following has broader representation:

European Commission: Scientific Committee Group on Occupational Exposure

Limits (SCOEL): Methodology for the derivation of occupational exposure

limits: Key documentation. Occupational Health and Hygiene, Plateau du

Kirchberg, Luxembourg. pp. 1-35. 1998

Tony

.......................................................................

" Tony " Havics, CHMM, CIH, PE

pH2, LLC

5250 E US 36, Suite 830

Avon, IN 46123

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