Dosing chemicals, notes

The lesion in the duodenum developed even more rapidly (e.g., perforation in 24 h after a single dose) and more predictably than with propionitrile. Acetanilide was the first aryl chemical noted to cause duodenal ulcer ( 18). Subsequently, 3,4-toluenediamine ( ) and 3,4-toluenedithiol (20) were also shown to induce duodenal ulcers and occasionally adrenal necrosis in rats. 

Table 21.1 shows a hypothetical data set for eight chemicals. Note that while some of the compounds affect tissues at very nearly equal doses, others are separated by one to two orders of magnitude. This example makes use of oral reference dose values, but in practice, values for acceptable levels could be TTVs, OETs, RfD, MRTs, or lTDs. In this example the lowest dose identifies the critical target organ and represents the oral RfD for each compound (denoted by ) secondary effects are also listed. Data on multiple effects for a single chemical will be used differently in the HI approaches presented, with differing results. 

Polymers. Ion implantation of polymers has resulted in substantial increases of electrical conductivity (140), surface hardness (141), and surface texturing (142). A four to five order of magnitude increase in the conductivity of polymers after implantation with 2 MeV Ar ions at dose levels ranging from 10 -10 ions/cm has been observed (140). The hardness of polycarbonate was increased to that of steel (141) when using 1 MeV Ar at dose levels between 10 -10 ions/cm. Conductivity, oxidation, and chemical resistance were also improved. Improvements in the adhesion of metallizations to Kapton and Teflon after implantation with argon has been noted (142). 

If there are specific data germane to the assumption of dose-additivity (e g., if two compounds arc present at the same site and it is known that the combination is five times more toxic than the sum of the toxicitics for the two compounds), then tire development of the hazard index should be modified accordingly. The reader can refer to the EPA (1986b) mi.xiure guidelines for discussion of a hazjird index equation that incorporates quantitative interaction data. If data on chemical interactions are available, but arc not adequate to support a quantitative assessment, note the information in the assumptions being documented for the risk assessment. 

Is die material classified as liighly toxic or toxic based upon die results of tests on laboratory animals e.g, LD50 or LC50 data. NOTE as described in Chapter 11, LD50 and LC50 arc referred to as the dose of a chemical that is lethal to 50 percent of laboratory test animals. 

The reader should note tliat since many risk assessments have been conducted on the basis of fatal effects, there are also uncertainties on precisely what constitutes a fatal dose of thennal radiation, blast effect, or a toxic chemical. Where it is desired to estimate injuries as well as fatalities, tlie consequence calculation can be repeated using lower intensities of exposure leading to injury rather titan dcatli. In addition, if the adverse healtli effect (e.g. associated with a chemical release) is delayed, the cause may not be obvious. Tliis applies to both chronic and acute emissions and exposures. 

BSI recommended water characteristics for coil boilers note that it is imperative that the oxygen scavenger used in coil boilers remove all the oxygen in the FW, so the use of a proportionally dosed, fully catalyzed chemical scavenger is essential. Sulfite may decompose at pressures higher than 50 bar and produce hydrogen sulfide or sul-fure dioxide in the steam. 

A method to estimate the optimal dose of a scale inhibitor has been described [1223]. The method starts with noting the chemical composition and temperature of the water. From these parameters a stability index is calculated, allowing for the prediction of the optimal dose of a scale inhibitor. 

It should be noted that automatic dosing and monitoring of dyes and chemicals can be used generally and is not restricted to pH control. 

Notes a. LD50 s are measured in mg/kg of bodyweight and are the dose at which 50% of the experimental animals die after exposure to a chemical. The smaller the number, the more toxic the pesticide. 

It should be noted that these considerations apply strictly to the consumables element. In the operation of a chemical dosing unit there is the additional fixed cost of manning the operation which, as noted above, is negligible for the catalytic reactor and process. 

No studies were located regarding reproductive effects in animals after dermal exposure to mirex. The only animal study that referred to reproductive effects following dermal exposure to chlordecone was conducted in rabbits by Allied Chemical. This study was not available for review. A published review of the study (Epstein 1978) indicated that chlordecone applied to shaved skin at dose levels of 5 or 10 mg/kg for 8 hours/day, 5 days/week, for 3 weeks induced testicular atrophy in two of six rabbits at 5 mg/kg and in one of six rabbits at 10 mg/kg. No other toxic effects were noted. This study is limited by the lack of dose response and lack of a NOAEL for the effect observed. 

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