Special Considerations

The dosimetric models described in the previous section apply to the vast majority of radionuclides of interest and may be used to determine their Q values and associated Aj and values. However, in a limited number of cases the models are inappropriate or require modification. The special considerations applying in such 

For alpha emitters it is not in general appropriate to calculate or Qg values for special form material, owing to their relatively weak gamma and beta emissions. In the 1973 edition of the Regulations an arbitrary upper limit for special form alpha 

A radionuclide is defined as an alpha emitter if in greater than 10 of its decays it emits alpha particles or it decays to an alpha emitter. For example, Np-235, which decays by alpha emission in 1.4 x 10 of its decays, is not an alpha emitter for the purpose of the special forms consideration. Similarly Pb-212 is an alpha emitter since its daughter Bi-212 undergoes alpha decay. Overall, the special form limits for alpha emitters have increased with increases in 

Finally, with respect to the ingestion of alpha emitters, arguments analogous to those used for beta emitters in the discussion on apply and the inhalation rather than the ingestion pathway is always more restrictive hence the latter is not 

The Aj and A2 values tabulated in the 1973 edition of the Regulations were subject to an upper cut-off hmit of 1000 Ci in order to protect against possible effects of bremsstrahlung. Within the Q system this cut-off was retained at 40 TBq. It was recognized as an arbitrary cut-off and is not specifically associated with bremsstrahlung radiation or any other dosimetric consideration. It remains unchanged. 

Exposure This term refers to the systemic exposure to drug-related material. It can be expressed as the plasma AUC of administered drug or metabolite within a dosage interval, typically assessed at steady state. The FDA metabolite safety draft guidance also uses the percent of the dose as the measurement of exposure to a metabolite. 

Major Metabolites The MIST document defines a major metabolite as one that accounts for 25% or more of the exposure to circulating drug-related material. The FDA draft guidance defines it as a metabolite in humans that accounts for plasma levels greater than 10% percent of the administered dose or systemic exposure, whichever is less. The major metabolite concept used in the FDA draft guidance refers to two types of metabolites (1) a circulating metabolite that accounts for 10% or more of the total drug-related components in the plasma, and (2) a metabolite that accounts for 10% or more of the administered dose. 

Unique Human Metabolites The FDA draft guidance document defines the term as a metabolite only in humans. The MIST document refers to a unique human metabolite as a metabolite identified in the plasma of humans but not in animals. However, it is very rare to find a truly unique human metabolite that is not formed in any animal species (Davis-Bruno and Atrakchi, 2006). 

Active Metabolites or Pharmacologically Active Metabolites The term refers to a metabolite that has target pharmacological activity greater than, equal to, or less than the parent drug. 

Important Active Metabolites The MIST document defines an important active metabolite as one which is deemed to make a significant contribution to the total known pharmacological activity of a given dose of the parent compound. The FDA draft guidance document does not use this term. 

Not unlike other nongenetic risk factors studied in epidemiological studies, analyses of gene-disease associations are also susceptible to various biases and confounders. Unfortunately, there are too many inconsistent results in the molecular epidemiological literature. We briefly describe below the main factors that contribute to such inconsistencies. 

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All metal parts exposed to the room are made of stainless steel and motors and transmissions are IP 65 to withstand the eflfect of the cleaning agents. The design also takes into account the special considerations necessary for food processing machinery with regards to easy accessibility to all parts and the lack of corners, edges, pockets or other food traps , so that the mechanical system can be easily cleaned. 

The most common types of aryl halides m nucleophilic aromatic substitutions are those that bear o ox p nitro substituents Among other classes of reactive aryl halides a few merit special consideration One class includes highly fluormated aromatic compounds such as hexafluorobenzene which undergoes substitution of one of its fluorines on reac tion with nucleophiles such as sodium methoxide... 

High temperature simulations require special consideration in choosing the sampling interval (see Step size on page 89). 

Avoiding sick building syndrome requires special consideration of building constmction and maintenance material used. Asbestos, organic solvents, paint sprays, dirty filters, moist environment caused by poorly maintained humidifiers, and dirty HVAC machinery have contributed to the deterioration of indoor air quahty. Nonstop quahty maintenance is required at all times. 

Certain apphcations require that the equipment meet FDA and USDA sanitary requirements. These requirements ensure that the products are not contaminated by extractables or microorganisms from the equipment. Special considerations are given to the design of such equipment (41—44) (see... 

Activated carbon generally presents no particular health hazard as defined by NIOSH (62). However, it is a nuisance and mild irritant with respect to inhalation, skin contact, eye exposure, and ingestion. On the other hand, special consideration must be given to the handling of spent carbon that may contain a concentration of toxic compounds. 

Catalysts often require activation or regeneration and their disposal also requires special consideration (56). 

Consteruatiou-applicatiou-specific details and special considerations... 

Y = coefficient naving value in Table 10-50 for ductile ferrous materials, 0.4 for ductile nonferrous materials, and zero for brittle materials such as cast iron t,n = minimum required thickness, in, to which manufacturing tolerance must be added when specifying pipe thickness on purchase orders. [Most ASTM specifications to which mill pipe is normally obtained permit minimum wall to be 12V percent less than nominal. ASTM A155 for fusion-welded pipe permits minimum wall 0.25 mm (0.01 in) less than nominal plate thickness.] Pipe with t equal to or greater than D/6 or P/SE greater than 0.385 reqmres special consideration. 

Some of the special considerations in regard to heat-exchanger corrosion are discussed in this subsection. A more extended presentation in Sec. 23 covers corrosion and its various forms as well as materials of construction. 

Certain corrosive conditions require that special consideration be given to complete drainage when the unit is talcen out of service. Particular consideration is required for the upper surfaces of tube sheets in vertical heat exchangers, for sagging tubes, and for shell-side baffles in horizontal units. 

Although the principles of multicomponent distiUation apply to petroleum, synthetic crude oil, and other complex mixtures, this subject warrants special consideration for the foUowing reasons ... 

An example of procedures found by performing a job task analysis would be rework procedures. Occasionally, out of specification product is produced which can be reworked in the process. This subcategoiy of normal operations phase procedures may require special consideration. While rework can be a straightforward operation, it could have safety consequences if done improperly. 

Tolling presents a special consideration that can make the training step easier. Typically a toller s technical staff, operators and mechanics are knowledgeable in the basic operations and tasks related to the toller s specialty. For example, experienced operators may know operations of the reactors, columns, exchangers, and packaging equipment quite well. The mechanical personnel may be very familiar with the required safe work practices, equipment cleaning procedures and maintenance tasks for standard vessels and piping. 

Special considerations need to be evaluated for decontamination and clean up of difficult materials. Eor example,... 

The same process will hold good for treating effluents from an eleciroplaiing shop should it alsocxi.sl with a paint shop. The effluents from an electroplating shop are strong wastes and need special consideration, as noted in the subsequent text and considered in Figure A 13.12. 

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