Absorption Mechanisms by Exposure Route

Each of these storage depots is further discussed to illustrate the relative importance of these two factors in determining where chemiccds will go in the body. 

Organ Total Blood Flow (ml/min) Organ Mass (% of body weight) Percent of Heart Output Relative Blood Flow (ml/min/lOOg) Percent Lipid Relative DDT Concentration (mg/kg)  

To do this efficiently, the blood flow through the kidneys must be high in order to filter a lot of blood very quickly. As a result of this high blood flow and the types of activities that occur in these organs, the liver and kidneys are primary sites of chemical storage. 

Fat has low blood flow. For example, five times more blood flows to the skin than to fat reserves (table 6.1). However, many chemicals are stored primarily in fatty tissues because they are lipophilic (fat-loving). For example, the distribution of DDT administered to laboratory rabbits through the diet was examined by chemically analyzing the organs. The results of this study indicated that roughly similar DDT concentrations were found in the brain and fat tissues, even though the brain receives 55 times higher blood flow than fat (table 6.1). 

However, because blood flow to the fat is very low, distribution into fat takes time. Therefore, a chemical like dioxin may first be distributed to the liver, but the amount in the liver will decrease with time as some reenters the blood supply and reaches fat cells. Some will also be metabolized by and interact with the liver, but the dioxin not affected by the liver will likely reach the fat cells. This phenomenon of a chemical having two different destinations over time is known as redistribution. 

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