Integration in human eye irritation

Assessment of Upper Respiratory Tract and Ocular Irritative Effects of Volatile Chemicals in Humans

Accurate assessment of upper respiratory tract and ocular irritation is critical for identifying and remedying problems related to overexposure to volatile chemicals, as well as for establishing parameters of irritation useful for regulatory purposes. This article (a) describes the basic anatomy and physiology of the human upper respiratory tract and ocular mucosae, (b) discusses how airborne chemicals induce irritative sensations, and (c) reviews practical means employed for assessing such phenomena, including psychophysical (e.g., threshold and suprathreshold perceptual measures), physiological (e.g., cardiovascular responses), electrophysiological (e.g., event-related potentials), and imaging (e.g., magnetic resonance imaging) techniques. Although traditionally animal models have been used as the first step in assessing such irritation, they are not addressed here since (a) there are numerous reviews available on this topic and (b) many rodents and rabbits are obligate nose breathers whose nasal passages differ considerably from those of humans, potentially limiting generalization of animal-based data to humans. A major goal of this compendium is to inform the reader of procedures for assessing irritation in humans and to provide information of value in the continued interpretation and development of empirical databases upon which future reasoned regulatory health decisions can be made.

A Proposed Approach for Setting Occupational Exposure Limits for Sensory Irritants Based on Chemosensory Models

OBJECTIVES

Setting occupational exposure limits (OELs) for odorous or irritating chemicals is a global occupational health challenge. However, often there is inadequate knowledge about the toxicology of these chemicals to set an OEL and their irritation potencies are usually not recognized until they are manufactured or used in large quantities.

METHODS

In this paper, the importance of accounting for risk perception and communication; conditioned responses; and interindividual variability in tolerance, detection and susceptibility with respect to setting an OEL are discussed in relation to three chemosensory models. These parameters and models were then used to construct a flowchart-style methodology that can be used to set an OEL for a specific chemical.

RESULTS

The OEL identified for a chemical odorant or irritant will depend on the type of chemosensory effect that the chemical is likely to exhibit. For example, experience has shown that chemicals with a low odor threshold often require low OELs even though many are not toxic or do not cause irritation at those air concentrations.

CONCLUSION

In order to establish the appropriate OEL, organizations need to agree upon the percentage of the workforce that they are attempting to protect and the types of toxicological end points that are sufficiently important to protect against (e.g. transient eye irritation, enzyme induction or other reversible effects). This is particularly true for sensory irritants. The method described in this paper could also be extended to setting limits for ambient air contaminants where risk perception plays a dominant role in whether the public views the exposure as being reasonable or safe.

Eye trigeminal sensitivity, tear film stability and conjunctival epithelium damage in 182 non-allergic, non-smoking Danes

The population distributions of CO(2)-induced irritation sensitivity in the eyes (COI), tear film stability (break-up time, BUT), and epithelium damage (ED) and the relation of these to basic potential confounders were assessed in an age- and gender-stratified random sample of citizens in Aarhus County, Denmark. One hundred eighty-two non-allergic, non-smoking persons participated. A general health questionnaire and an indoor air questionnaire was filled out before the measurements. The BUT was non-normally distributed, as was COI at 16% CO(2) and single ED-scores. However, COI average for all levels was normally distributed and the total score for ED was only marginally deviating. BUT decreased, the threshold to CO(2) increased, and irritation intensity at CO(2) eye exposure decreased with increasing age. ED was increased among women. There were no internal relations between the three measures, but reduced BUT was seen among subjects rating high levels of exposure to dust, electrostatic fields, and dry air. ED decreased by perceived unpleasant odors and increased with experiences of high temperatures. CO(2) sensitivity increased by perceived draught, dry air, and noise exposure prior to measurements. Selection bias cannot be excluded and the results may therefore not be truly representative of the general population. However, the results may be used as reference data for future use of measurements of break-up time, epithelium defects, and CO(2) sensitivity of the eyes in the indoor air.

PRACTICAL IMPLICATIONS

The most direct implication is that results can be used as reference level for measurements in problem buildings and for individual measurements. The reference can also be used in research and the other results as basis for future hypotheses and for support of existing hypotheses.

A critical appraisal of current knowledge and future directions of ergophthalmology: consensus document of the ICOH Committee on 'Work and Vision'

In the past, occupational health gave scant attention to the visual apparatus. Studies on issues relating to 'work and vision' have predominantly addressed industrial accidents and the toxic effects of exposure to chemical and physical agents, with secondary prevention being more common than primary prevention. In recent years, the huge transformations implemented in workplaces, mainly due to computer-based technologies, demand a progressively higher efficiency of the eye and the related nervous system components that co-ordinate eye movements and accommodation. At the moment these aspects are managed by medical, psychosocial and a variety of technical disciplines, without any shared criteria, terminology and method. Objectives of the Committee are: to investigate holistically the many possible hazards associated to the occupational visual performance; to come to a consensus on terminology, risk assessment and health surveillance procedures. The present status of research and practice in ergophthalmology does not allow for clear-cut decision about health risk and nor is there a clear direction on the prevention of work-related ocular and visual disturbances and disorders. Specifically, at least three determinants must be objectively considered, namely: (a) visual effort; (b) environmental agents; (c) individual characteristics. Although criteria exist for the evaluation of some of these determinants, a greater refinement is necessary 'for a good working life' of the visual apparatus. The ICOH Scientific Committee on 'Work and Vision' is seeking to systematically develop this matter, yielding a more rational and complete approach to the relationship between work and vision.