Malodorants exposure

Many malodorous compoimds are not only nuisance, but also a health threat under prolonged exposure [1]. Ammonia (NH3) is emitted from landfill and sewage treatment plant and associated with many agricultural activities (e.g. poultry and piggery). Ammonia is also a problem in public toilets, hospitals and nursing homes. Selective eatalytie oxidation (SCO) can convert NH3 to N2 at mild temperature (i.e. 473-673 K) as shown in equation 1, however nitrous oxides (N2O) and nitrogen oxides (NOj) are often produced cf. Eqn. 2 3). 

In a report comparing community responses to low-level exposure to a mixture of air pollutants from pulp mills, Jaakkola et al. (1990) reported significant differences in respiratory symptoms between polluted and unpolluted communities. The pollutant mixture associated with the pulp mills included particulates, sulfur dioxide, and a series of malodorous sulfur compounds. Major contributors in the latter mixture include hydrogen sulfide, methyl mercaptan, and methyl sulfides. In this study the responses of populations from three communities were compared, a nonpolluted community, a moderately polluted community, and a severely polluted community. Initial exposure estimates were derived from dispersion modeling these estimates were subsequently confirmed with measurements taken from monitoring stations located in the two polluted communities. These measurements indicated that both the mean and the maximum 4-hour concentrations of hydrogen sulfide were higher in the more severely polluted community (4 and 56 g/m3 2.9 and 40 ppb) than in the moderately polluted one (2 and 22 g/m3 1.4 and 16 ppb). Particulate measurements made concurrently, and sulfur dioxide measurements made subsequently, showed a similar difference in the concentrations of these two pollutants between the two polluted communities. 

A subsequent report by Marttila et al. (1994b) examined the impact of long-term exposure to the same mixture of malodorous sulfur compounds on children from these same three communities. The findings in children, i.e., nasal symptoms and cough, in the most severely polluted community were similar to those reported above and showed increased risks both for the 4-week and the 12-month intervals, although none of these risks reached statistical significance. 

Marttila et al. (1995) also examined the relationship between daily exposure to malodorous sulfur compounds (measured as total reduced sulfur [TRS]) from pulp production and experience of symptoms in a small population living in the vicinity of a pulp mill. The major components of the malodorous sulfur compounds are hydrogen sulfide, methyl mercaptan, and methyl sulfides. This work was initiated due to the observation that an unusually high short-term exposure to malodorous sulfur compounds (maximum 4-hour concentrations of hydrogen sulfide at 135 g/m3 [96 ppb]) led to a considerable increase in the occurrence of ocular, respiratory, and neuropsychological symptoms (Haahtela et al. 

Martilla O, Jaakola JJK, Partti-Pellinen K, et al. 1995. South Karelia air pollution study Daily symptom intensity in relation to exposure levels of malodorous sulfur compounds from pulp mills. 

Partti-Pellinen K, Martilla O, Vilkka V, et al. 1996. The South Karelia air pollution study Effects of low-level exposure to malodorous sulfur compounds on symptoms. Arch Environ Health 51 315-320. 

Malodorants are primarily an inhalation hazard. Aerosols and vapors are extremely foul smelling at low concentrations but are otherwise relatively nontoxic. However, exposure to bulk liquid or solid agents may be hazardous through skin absorption, ingestion, and introduction through abraded skin (e.g., breaks in the skin or penetration of skin by debris). 

Malodorants do not seriously endanger life except at exposures greatly exceeding an effective dose, usually only achieved in a confined or enclosed space. 

Casualties will usually recover from exposure to malodorants shortly after removal from the contaminated atmosphere. Most patients can be discharged safely. Rarely a patient with significant respiratory findings may merit admission. 

At concentrations below those necessary to produce toxic effects, ethyl mercaptan is extremely malodorous and voluntary exposure to high concentrations is unlikely to occur. Observations on humans are limited to a single brief report of exposure of workers to 4 ppm for 3 hours daily over 5-10 days the workers experienced headache, nausea, fatigue, and irritation of mucous membranes. ... 

A word of caution about toxicity. Many of these compounds are so malodorous it is unlikely anyone could tolerate lethal concentrations of them. Just the same, one should remember that they are toxic and that exposure to them should be minimized. They should only be handled in hoods with good drafts. On human skin, poly(thioformaldehyde) causes dermatitis. Its LDS0 in rats is 365 11 mg/kg (21). 

New polymer-supported reagents for sulfide transfer have been developed to avoid exposure to malodorous and toxic sulfur reagents. Ley et al.15 prepared a stable aminothiophosphate polystyrene resin for the conversion of secondary and tertiary amides to thioamides in high conversion and purity (Table III, entry 11). This procedure is extremely clean and affords the desired product with short reaction times in comparison to Law-esson s reagent. In addition, the aminothiophosphate resin dehydrates primary amides to nitriles. 

Figure 17 During 5 min subjects were exposed to the E-isomer of the ethyl ester of 3-methyl-2-pentenoic acid (E-EE3M2PA), which has a floral odor. Every 15 sec they were asked to rate the intensity of either E-EE3M2PA or mercaptoethanol (a sulfurous malodor) across 11 min (except for the 1 min between adaptation to E-EE3M2PA and recovery from adaptation). Relative to estimates of perceived intensity that were obtained before adaptation, the perceived intensity of E-EE3M2PA decreased during repeated exposures to the odorant (adaptation). There also was a significant decrease in the perceived intensity of mercaptoethanol during exposure to E-EE3M2PA (cross-adaptation).

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