Average body burden

Comparison of Estimated Body Burdens Associated with Effects in Experimental Animals and Humans. Estimated average body burdens of 2,3,7,8-TCDD in human populations in which various health effects of 2,3,7,8-TCDD are suspected range from 31 to 6,600 ng/kg (estimated body burdens at the time of exposure termination). See Table 2-1 for more information. The human body burden expected in populations exposed to background environmental levels of 2,3,7,8-TCDD has been estimated to be 1 ng TCDD/kg body weight (DeVito et al. 1995 Orban et al. 1994). This would suggest that effects of 2,3,7,8-TCDD in humans may occur at body burdens that are 30 to 6,600 times greater than background burdens for 2,3,7,8-TCDD. 

The present average body burden of strontium-90 in the world s population is about 0.0002 uc. per person. This corresponds, with Dr. Finkel s conversion factor (5 to 10 /tc. per 70-kg man equivalent to 1 /xc. retained per kg for mice) to a retained dose a = 0.00002 to 0.00004 /xc/kg in mice. Hence in order to justify Dr. Finkel s statement evidence would be needed that the mouse threshold is as great as about 0.00004 /xc/kg that is, we must place a in equation (28) equal to 0.00004 gc/kg. From the values of the constant v in Table 2 (we use the values for v = 170 days, which we believe to be better than those for a = 284 days) we find M = 1 X 10 for the minimal test and 3.4 X 10 for the most powerful test with 10 per cent type-II error, and 3.3 X 10 and 13.5 X 10, respectively, with 1 per cent type-II... 

The body excretes tritium with a biological half-life of 8—14 d (10.5 d average) (75), which can be reduced significantly with forced fluid intake. For humans, the estimated maximum permissible total body burden is 37 MBq (1 mCi). The median lethal dose (LD q) of tritium assimilated by the body is estimated to be 370 GBq (10 Ci). Higher doses can be tolerated with forced fluid intake to reduce the biological half-life. 

Blood lead levels, urinary lead levels, serum creatinine, blood urea nitrogen (BUN), creatinine clearance (CCT), and NAG were measured in 158 male and 51 female workers in a lead battery factory or a lead smelting plant in Japan (Ong et al. 1987). Controls consisted of 30 professional and laboratory staff members with no history of renal disease or lead exposure. The length of exposure to lead averaged 10.8 8.0 years with a range of 1-36 years. Exposure levels were not available, but indicators of lead body burden in the exposed workers were PbB level = 3.0-80.0 pg/dL and urinary lead level =... 

Substantial progress in reducing lead body burdens has been made in the past three decades (e.g., by programs to eliminate leaded gasoline and to prevent children s exposure to leaded paints present in many older homes), and the most recent nationwide surveys have revealed that average blood levels in children are now near 2 pg/dl. There are still subpopulations showing excessive exposure, probably related to paint found in older homes. In some areas of the world, particularly where leaded gasoline is still used, the problem remains serious. The problem is complicated by the fact that, as we have worked to reduce lead exposures, health scientists have uncovered new concerns. 

In a similar study, Levesque et al. (1994) attempted to quantitate the body burden of chloroform following exposure in an indoor pool. Scuba divers were exposed to chloroform-laden water and air on each of seven days. On each exposure day, the subjects exercised for a 55-minute period alveolar air samples were collected before exercise and after 35 or 55 minutes of exercise. Pre-exercise alveolar levels of chloroform averaged 52.6 ppb this was attributed to air contamination in the locker room. Alveolar air concentrations of chloroform after 35 and 55 minutes of exercise increased steadily through day 5, averaging 100-950 and 104-1,093 ppb, respectively. On day 6, when scuba gear was worn by the subjects, alveolar air concentrations after 35 and 55 minutes of exercise were 196 and 209 ppb, respectively. The authors concluded from this data that the average proportion of body burden due to inhalation after 35 and 55 minutes exercise was 76 and 78%, respectively. 

Muller et al. 1975). Pavlovskaia et al. (1974a) determined that the excretion of intratracheally-administered thorium-228 (as thorium dioxide or thorium chloride) in the feces occurred in two phases in the rat in the first phase, up to 60% of the thorium-228 contained in the body was eliminated, and in the second phase, the rate of thorium-228 excretion in the feces averaged 0.25% of the body burden daily. 

Polybrominated Biphenyls. Body burden data indicate that low-level exposures to PBBs have occurred for people in the state of Michigan. No recent information about average daily intake of PBBs was located. The levels of PBBs in human tissue and body fluids, such as blood, serum, adipose tissue, breast milk, feces, cord blood, biliary fluid, and placenta, of people in the state of Michigan have been extensively studied (Brilliant et al. 1978 Cordle et al. 1978 Eyster et al. 1983 Humphrey and Hayner 1975 Lambert et al. 1990 Landrigan et al. 1979 Wolff et al. 1982). However, no recent data are available. Data on the levels of PBBs in tissues and body fluids of residents who live in the vicinity of sites of industrial discharge of PBB wastes were not located. Updated infonnation would be useful to understand current exposure levels of people in the state of Michigan to PBBs. This information is necessary for assessing the need to conduct health studies on these populations. 

It is particularly interesting to evaluate the contribution of a major nuclear facility, such as the Savannah River Plant, to the radiation dose to the population. Inasmuch as Beaufort, S. C., receives its drinking water primarily from the Savannah River, the expected body burdens may be extrapolated from tritium concentrations of the river at Beaufort. As mentioned previously, the difference between the concentrations at Augusta, Ga., and Beaufort, S. C., may be attributed to the operation of the Savannah River Plant. The difference averages approximately 4 nCi/liter and corresponds to 0.8 mrem./a. This represents 0.5% of the radiation protection guide for an average dose to a suitable sample of the population. 

POPs in the environment can enter the food chain, bio-accumulate and bio-magnify as they move up the trophic levels and ultimately end up in the human body. It is expected that POPs will continue to accumulate in the body fat and their average concentrations will increase with age. The level of POPs contamination in human blood/serum and breast milk can serve as a good indicator of their body burden. 

TCDD in serum lipid is in equilibrium with total body lipid 2,3,7,8-TCDD concentrations and that in an average adult 22% of the body weight is lipid. Body burdens were calculated (see Table 2-1) for the human studies reporting serum (or tissue) lipid 2,3,7,8-TCDD concentrations. If only current serum... 

As a result of the transfer of CDDs through the placenta to the fetus, by breast milk to infants and young children, and by lifelong dietary intakes from the consumption of meat, milk and dairy products, and fish, CDDs are found to be widespread in the adipose tissue of members of the general population (Orban et al. 1994). Human adipose samples from the recent 1987 NHATS Study provide a representative sample of CDD body burden in the general U.S. population (see Section 5.5.1). The average concentration of 2,3,7,8-TCDD in the U.S. population was estimated to be 5.38 pg/g ( 6%). The 1987 survey data clearly... 

The available sample size for kidney, brain, liver, and gut varied from 20 to 100 grams. Replicate assays of these samples did not agree and recovery studies indicated that these assays were not quantitative. Assays of one whole kidney showed significant differences between the concentrations of DDT plus DDE in the cortex and the medulla. The precision and the accuracy, as measured by recovery studies of replicate samples from homogenized portions of either the cortex or the medulla, were within the limits considered acceptable for this method. With the realization that it was impossible to obtain reliable data on the samples as they had been collected, an arithmetic average of all replicate assays for the organs from four cadavers was used to estimate the total body burden. Cadavers 3, 10, 14, and 18 were studied. 

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