Offending substance

Irritant contact dermatitis is not the result of an immunologic process, but rather occurs from direct injury to the skin. An irritating agent comes into contact with the skin, damages the protective layers of the epidermis and can cause erythema, the formation of vesicles, and pruritus.25,29,30 Symptoms occur within minutes to hours of exposure and begin to heal soon after removal of the offending substance.27... 

External/Skin Decontamination. This entails the complete removal of clothing and gentle washing of the victim with copious amounts of lukewarm water. Mild soaps are often useful and may increase effectiveness of the removal of the offending substance. 

Often the most difficult step follows the identification of the odor substance finding the cause of the presence of this substance in the packaging in order to avoid future quality problems. To do this it is advantageous to have as much information as possible on the chemical composition, treatment, and complete history of the package. With this information, it is sometimes possible to discover a reaction pathway for the offending substance or substances. 

Another characteristic of irritative stimulation of the trigeminal nerve is the defensive reflexes (e.g., sneezing) invoked by the body to remove or dilute the offending substance. In the case of oral chemical heat, the burning sensation from capsaicin invokes sweating, tearing, and copious salivation. Salivary flow... 

The patient with toxic keratitis or medicamentosa generally reports recent exposure to the offending substance or the use of an ophthalmic preparation on a short- or long-term basis. In the case of mild toxic keratitis, the patient may have few or no symptoms. More involved cases may produce very definite symptoms of redness, irritation, burning, tearing, and ocular discomfort upon instillation. 

Differential diagnosis includes irritant contact dermatitis and allergic contact dermatitis. History of exposure to an offending substance assists in making the differential diagnosis. 

Box 27-1 summarizes a variety of offending substances that are involved in contact dermatitis, which include... 

Aristolochic acids (AA) were thus considered as the offending substance because AA induced nephrotoxic effects in experimental animals [44] as well as in human beings [45]. They also induced carcinomas in rodents [46]. 

To protect patients and health care workers, it is essential to determine the responsible hazardous chemical as early in the decontamination process as possible. Based on previous experience with hazardous exposures, the National Institute of Occupational Safety and Health (NIOSH) and the Environmental Protection Agency (EPA) recommend level B protection as a minimal precaution (see Table 3.1) before the offending substance is identified (11). However, if available evidence suggests that the substance involves the skin as a route of exposure or is dangerous by dermal absorption or corrosion, health care workers and others coming in contact with victims require the additional skin protection of Level A PPE (9). 

If the technology is accessible and the cost of applying it is not too great, precombustion removal of potential air pollutants has substantial merit. At this stage the offending substance (or substances) present in the raw material has not as yet been burned or reacted to form the process exhaust gases, which should make recovery easier. 

If the offending substance is an acid or a base, check the pH of the victim s tears after irrigation and continue irrigation if the pH remains abnormal. 

Patients may also be patch tested with a swatch of the suspected fabric, applied dry and/or wet. If the patient is patch-test positive, this identifies the fabric that contains the offending chemical. However, a negative does not rule out the possibility that the fabric does contain the allergen. The conditions may not permit the transfer of the offending substance or may not permit transfer at sufficient concentrations to elicit a response, and without that essential transfer step, a positive will not occur. At one time, it was recommended that the fabric should be steamed prior to application, but that recommendation has been withdrawn (Foussereau 1992). 

Commonly, workers clothes become begrimed with the offending substance, making close contact with the scrotum, the wrinkled skin of which favours the harbouring of the carcinogen. 

Some chemicals act as sensitisers provoking an unpleasant response, usually in the lungs or the skin, from a very small quantity of the offending substance. This process is caused by a response of the body s immune system to foreign material. 

A second application route was discovered when asthma or bronchial reactions were noted by many sufferers. Thus, the offending substances were acting through inhalation. A third method of introducing the toxins was by direct injection the effects of curare and other poisons (68) have been described. Finally, all three possible application routes of intoxication (or a combination of them) may be necessary to cause the development of various cancers (121). 

Illustration 6.3 Discharge of Plant Effluent into a River We consider here the case of process water saturated with benzene being discharged into a river. The question to be addressed is whether the diluting effect of the river flow is sufficient to reduce the effluent concentrahon to within permissible limits and, if not, how much of the offending substance has to be removed to meet environmental standards. A sketch depicting effluent and river flow is shown in Figure 6.3. 

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