Secondary contamination effects

Respiratory Effects. One study suggested increased respiratory disorders (asthma, bronchitis, pneumonia) in children with chronic exposure to a solvent-contaminated water supply (Byers et al. 1988). Two municipal wells in eastern Woburn, Massachusetts, were found to contain several solvents including trichloroethylene (267 ppb) and tetrachloroethylene (21 ppb). The increased susceptibility to infection may be secondary to effects on the immune system. Accurate chemical-specific exposure levels for individuals could not be determined because the water distribution system was designed to use water from different wells at different rates and times. Other limitations of this study are described in Section 2.2.2.8. 

If only some of the peaks tail, secondary retention effects, such as residual silanol interactions, may take place. Another possibility is that a small peak is eluting on the tail of a larger peak. If all peaks tail, this may be due to a bad column or build up of contamination on the column inlet frit. 

Rapid rescue from the hot zone represents the mostpractical and effective operational approach and in most major releases the most effective health response is likely to be focused in the more lightly contaminated ( warm ) and uncontaminated ( cold ) zones. There - and at receiving hospitals - the main emphasis should be on providing the type of respiratory and physical protection for staff so that secondary contamination is prevented. Unprotected staff should not come into contact with undecontaminated patients. 

Commercially available silicas differ in their physical (specific surface area, mean pore diameter, pore volume, etc.) and chemical (contamination of different metals such as Al, Mg, Fe) characteristics. These metal contaminations can cause secondary retention effects (e.g., strong tailing of basic solutes). Additionally, commercial silicas differ widely in their Na content. The higher the Na content of the silica, the more alkaline its behavior in contact with water. This often acts as a catalyst for the hydrolysis of the Si -C bonds of chemically modified silica phases (see Section 12.4.3). Good silicas have an Na content of < 30 ppm. Excessively high contents of metal contaminants could easily be removed by the manufacturer by means of a thorough acid-washing... 

This depends on the concentration and inherent toxicity of the chemical with which a patient is contaminated and the proximity and duration of contact with the staff. Chemical agents can be present on the patient s skin, hair and clothes, all of which can be reduced by external decontamination. However, certain volatile agents may also be present in exhaled breath ( respiratory off-gassing ) and ingested chemicals may be present in vomitus, neither of which is removed by external decontamination. In these circumstances, regular rotation of staff away from the clinical areas may reduce the effects of secondary contamination. 

Avitrol [504-24-5] (4-anHnopyridine) (24), mp 155—158°C, bp 273°C, has repeUent—toxicant properties for birds and is classed as a severe poison and irritant. This secondary bird repeUent can be used as a broadcast bait, causing uncoordinated flight and distress caUs and escape responses in nearby birds (57). A reevaluation shows lack of effectiveness of 1% baits but better control of blackbirds with 3% baits (58). Suspected contamination of drinking water with 4-aminopyridine has been reported in toxicosis of Brahman catde and horses (59). 

Color can be removed effectively and economically with either alum or ferric sulfate at pH values of 5—6 and 3—4, respectively. The reaction is stoichiometric and is a specific reaction of the coagulant with the color to form an insoluble compound (17). The dosage required may be as high as 100—150 mg/L (380—570 mg/gal). Raw-water colors may be as high as 450—500 units on the APHA color scale. The secondary MCL (maximum contaminant level) for color in the finished water is 15 units, although most municipal treatment plants produce water that seldom exceeds 5 units. 

A SSIMS spectrum, like any other mass spectrum, consists of a series of peaks of dif ferent intensity (i. e. ion current) occurring at certain mass numbers. The masses can be allocated on the basis of atomic or molecular mass-to-charge ratio. Many of the more prominent secondary ions from metal and semiconductor surfaces are singly charged atomic ions, which makes allocation of mass numbers slightly easier. Masses can be identified as arising either from the substrate material itself from deliberately introduced molecular or other species on the surface, or from contaminations and impurities on the surface. Complications in allocation often arise from isotopic effects. Although some elements have only one principal isotope, for many others the natural isotopic abundance can make identification difficult. 

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