Biological damage

Ozone, which occurs in the stratosphere (15—50 km) in concentrations of 1—10 ppm, is formed by the action of solar radiation on molecular oxygen. It absorbs biologically damaging ultraviolet radiation (200—300 nm), prevents the radiation from reaching the surface of the earth, and contributes to thermal equiHbrium on earth. 

Fig. 2. Sources of potential biological damage in the immediate vicinity of a power station cooling system where the condenser may sustain mechanical...

One potential risk that formulators run when using cosolvents as drug solubilizers is the possibility of vehicle toxicity. Each cosolvent is characterized by an acceptable concentration range, which cannot be exceeded without incurring biological damage. To avoid the requirement for in vivo testing, several in vitro models have been advanced to evaluate the relative safety of cosolvent excipients. The most useful in vitro procedure follows the hemolysis of red blood cells, which has been correlated with in vivo animal tests [87,88]. 

Linear hypothesis The assumption that any radiation causes biological damage in direct proportion of dose to effect. 

It is well established that both ozone and PAN can cause damage to. biologic ems (see Chapters 8 and 11). The possibility that the reactive intermediates in smog could directly cause biologic damage has been suggested, but experiments are seldom designed to test this possibility. 

It is known that free radicals are formed when ozone reacts with carbon-carbon double bonds. Recently, it has been suggested that PAN probably forms free radicals when it reacts with aldehydes. Because hydroperoxy radicals are free radicals, they may have biologic effects similar to those of ozone and PAN. Certainly, for experiments in which the observed biologic damage cannot be attributed to the measured concentrations of ozone and PAN, free radicals or unstable compounds should be considered. 

No internalization of E. coli 0157 H7 in spinach plants when subjected to physical or biological damage 2000 ppm sodium hypochlorite Hora et al. (2005)... 

The volumetric power deposition calculated for bound water was appreciably greater—up to about five times—than that for free water the maximum difference occurs near the bound water relaxation frequency. This enhanced energy deposition is localized in the bound water shell and therefore may cause more damage than if it were distributed uniformly throughout the medium. But Dawkins et al. consider the enhancement of biological damage by localiza-... 

Because the ground state of the sensitizer Is regenerated the reaction is catalytic. Once formed the activated species of oxygen, 02 from type II reactions 0 from type 1 mechanisms cause biological damage by oxidation of biological molecules. 

Nitrogen dioxide s claim to fame comes from two major sources, environmental pollution (214) and the possibility that NO2 is responsible for some of the biological damage attributed to peroxynitrite (215,216) from which it is formally derived by 0-0 bond homolysis. 

Gray LH (1954) Conditions which affect the biologic damage resulting from exposure to ionizing radiation. Acta Radiol 41 63-83... 

K.I. Morton, G.R. Ter Haar, I.J. Stratford and C.R. Hill, Subharmonic emission as an indicator of ultrasonically-induced biological damage, Ultrasound Med. Biol. 9 (1983) 629-633. 

Various refinements of the REC concept have been suggested, such as the use of rad-equivalents.111 The chemical dose would be determined from the chemical damage to the DNA or other macromolecules and related to the radiation dose that causes a corresponding degree of biologic damage. However, despite its novelty and theoretical attractiveness, the procedure suffers from most of the difficulties that make the REC concept inapplicable for risk estimation. 

Sometimes terms pathological and physiological resin are used. Pathological resin, located in resin canals, is mainly composed of resin acids and monoterpenes and protects the wood against biological damage. Physiological resin, located in the ray parenchyma cells, is rich in fats and constitutes a supply of reserve food. Hardwoods contain only this type of resin. 

Another unit that appears in some texts is the rad which is 10 J of energy deposited per kilogram of tissue. Because different particles and radiations produce different damage, both the type and dose of radiation and effectiveness to produce biological damage must be considered. The unit rem is sometimes used ... 

---