Nitrate, estimating exposures

In some cases it is possible to differentiate between the various alkyl substituents. Primary, secondary and tertiary nitrates and nitrites all show clearly different infrared absorptions. The spectra of acid fluorides can be used to differentiate chain-end groups from pendant acid groups. Furthermore, the loss of all -OH species upon sulfur tetrafluoride exposure allows the reliable estimation of ketones, esters and lactones without the complication of hydrogen-bonding induced shifts in the spectra. Preliminary results from the use of these reactions to characterize y-ray oxidized polyethylene and polypropylene are used to illustrate the scope of the methods. 

None of the exposures produced changes in clinical chemistry values (blood count, blood nitrate, blood urea nitrogen, serum enzymes, and serum electrolytes or urinalysis and nitrate and nitrite urinary excretion), spontaneous electrical activity of the cortex of the brain (detected by EEG), pulse rate and sinus rhythm, or pulmonary function. Visual and auditory acuity, exercise EKG, and time estimation tests did not differ from control values for any of the exposures. Only one of several cognitive tests was affected by exposure and the change occurred only in the four subjects exposed at 1.5 ppm. The test was taken during the time the subjects were experiencing severe headaches. 

Gastrointestinal Effects. Abdominal pain has also been reported by workers exposed to silver nitrate and oxide in the workplace (Rosenman et al. 1979). The pain was described as "burning in quality and relieved by antacids" and was reported in 10 out of 30 workers examined. Exposure levels were estimated to be between 0.039 and 0.378 mg silver/m. No information on chemical form or particle size was provided. Duration of employment ranged from less than one, to greater than ten years. 

Absorption of silver nitrate across intact skin has been demonstrated in guinea pigs and is similar to that of intact human skin (Wahlberg 1965). The amount absorbed was estimated to be approximately 1 % of the applied dose within 5 hours of exposure. Silver administered in the form of silver sulphadiazine cream was minimally absorbed through both the intact and burned skin of rats and distributed throughout the body (Sano et al. 1982). The absorption of silver increased through burned skin after blister removal. The authors did not determine the percentage of the applied dose that was absorbed (Sano et al. 1982). 

As with the metals and metalloids mentioned earlier, the dietary exposure to nitrate in the UK has been monitored for a number of years. A Total Diet Study (TDS) carried out for samples purchased in 1997 found that dietary exposures for the general population were lower than for the comparable study carried out in 1994.48 The population average dietary exposure for 1997 was 52 mg/day compared with 68 mg/day in 1994, the decrease being partly explained by lower nitrate concentrations found in green vegetables. From the same study, the mean and 97.5th percentile exposures were 57 mg/day and 136 mg day respectively. The estimate for a mean consumer in 1997 was considerably lower than the ADI for nitrate of 219 mg/day for a 60 kg person, even allowing for additional exposure from water and beer, giving a total of 88 mg/day. 

The most common route of exposure is by oral ingestion of nitrosamines in food. It has been estimated that the general population consumes approximately 0.1 (ig of nitrosamines per day in their diet. Nitrosamines can be found in foods preserved with nitrates as well as in untreated foods such as mushrooms, alcoholic beverages, smoked fish, bacon. 

Suh (USA) 2004 Determination of concentrations of and exposures to pollutants in Los Angeles homes Black carbon, nitrate Exposure estimate ranges (Hg/m )... 

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