Lead absorber

An average adult breathes about 8.50 X 103 L of air per day. The concentration of lead in highly polluted urban air is 7.0 X 10 6 g of lead per one m3 of air. Assume that 75% of die lead is present as particles less than 1.0 X 10 6 m in diameter, and that 50% of die particles below that size are retained in the lungs. Calculate the mass of lead absorbed in this manner in 1 year by an average adult living in this environment... 

Infants from birth to 2 years of age have been shown to retain 31.7% of the total amount of lead absorbed (Ziegler et al. 1978), whereas adults retained only 1% of an absorbed dose of lead (Rabinowitz et al. 1977). 

Example Problem Estimate the fraction of 1.0 MeV photons that will be transmitted through a lead absorber that is 5 cm thick (the thickness of lead bricks commonly used in radiation shields). 

Ingestion. Absorption influenced by form, particle size, and iron and calcium absorption. More ingested lead absorbed in children than adults Percutaneous. Orgartic lead compounds readily absorbed. 

The effect of Pb on freshwater fish varies depending on the species of fish. Goldfish, for example, are relatively resistant to lead, presumably due to their abundant gill secretion. As mentioned above, following the ingestion of expended lead shots in lakes or in the field, more than one million birds are estimated to be killed each year in the U.S. Lead absorbed by the bird paralyzes the gizzard leading to starvation, and death usually follows within several weeks after the exposure. 

Graphically verify Eq. (1-13) for a lead absorber and Mo Kv., Rh Ka., and Ag Ka radiation. (The mass absorption coefficients of lead for these radiations are 122.8, 84.13, and 66.14 cm /gm, respectively.) From the curve, determine the mass absorption coefficient of lead for the shortest wavelength radiation from a tube operated at 30,000 volts. 

Exposure. This reflects the amount of lead in the environment to which the particular individual is exposed. Any effects will depend upon the amount of lead absorbed, which will depend upon the intensity and duration of exposure. 

Absorption. Lead can be absorbed either from the air or from ingested food or fluid [2]. The amount of lead absorbed by inhalation increases with increasing particle size. Much lead, however, is absorbed from the alimentary tract where food and water may contain lead or be contaminated with lead-containing soil or dust. The lead content of food will depend upon the environment in which it is grown. Most ingested lead traverses the alimentary tract and is excreted in the faeces, the amount absorbed depending upon the amount ingested. 

Determination of Mo Impurity. Determination of Mo should be performed with a sample of the fresh eluate (37 MBq) by y-spectrometry. A lead absorber 6-mm thick is placed between the sample and the Nal-detector. The fraction of y-radiation measured at 740 keV ( Mo) should not exceed the reading obtained with a reference... 

The amount of lead absorbed from the gastrointestinal tract of adults is typically 10 to 15% of the ingested quantity for pregnant women and children, the amount absorbed can increase to as much as 50% (Agency for Toxic Substances and Disease Registry, 1992). 

Experimenters could use these rare but extremely radioactive elements in particle guns. Lead absorbs the radiation. If a bit of material containing one of these elements is placed in a lead-lined box with a hole in it, almost all the particles that come flying off are absorbed by the lead. Some, however, make their way through the hole to compose a thin stream of very many, very energetic particles which can be directed at some target. 

The amount of lead absorbed can be affected by nutrition. More lead is absorbed with inadequate intake of iron, calcium, vitamin C, or zinc. 

The medical surveillance section of the standard also contains provisions dealing with chelation. Chelation is the use of certain drugs (administered in pill form or injected into the body) to reduce the amount of lead absorbed in body tissues. Experience accumulated by the medical and scientific communities has largely confirmed the effectiveness of this type of therapy for the treatment of very severe lead poisoning. On the other hand, it has... 

I n fact, considering the scattering of nonresonant gamma quanta (in region Ey = 14.4 keV) from lead absorber, which increases this increase of lifetime r is even greater. 

Using classic balance study techniques, Kehoe (1961) established that gastrointestinal absorption of lead by adult males was 5-10% of ingested lead at typical and elevated levels of lead exposure. More recently these values for percentage lead absorbed by the adult male under circumstances of normal dietary intake were confirmed using either shortlived radioisotopes (Hursh and Suomela 1968) or stable isotopes of lead (Rabinowitz et al. 1980). 

Alpha radiation is produced by a radioactive source and formed into a beam by a lead plate with a hole in it. (Lead absorbs the radiation.) Scattered alpha particles are made visible by a zinc sulfide screen, which emits tiny flashes where particles strike it.A movable microscope is used for viewing the flashes. 

Experiments were made on the lead-dissolving power of cassia oil. 10 c.c. of the lead-free cassia oil was introduced into each of 22 test tubes, together with a strip of bright lead about 1 cm. broad and 6 cm. long. The tubes were then closed with clean corks, shaken at intervals, and tested at intervals. The amount of lead absorbed increased with the time, and reached a mammum of 0 074 per cent, after one month, and then seemed to remain constant. It is noteworthy that after that period the lead content exceeds the percentage found in commercial samples, which is, as a role, from 0 04 to 0 06 per cent. 

A 4 cm thick lead absorber is placed between the sample and the detector... 

The conditions for the determination of nitrogen in niobium and tantalum (42)(45)(46) using the N(p,n) 0 reaction are similar to those described under 2.3 except for the irradiation (12 MeV protons, 0.5 lA for Nb and 3 to 4 /.A for Ta) and measuring conditions (No lead absorber needed, detector with 5 % relative detection efficiency). 

Replace the aluminium absorber (1335 mg cm ) by a copper absorber of the same thickness on the second shelf and count for 200 seconds. Repeat using instead of copper, lead absorbers of the same thickness. Repeat using an iron absorber instead. 

Change the position of the Sr source by moving it to alter the angle of scatter and place the lead absorber used previously and count for 200 seconds. 

It has been shown that there is little translocation of absorbed lead in terrestrial plants, with lead being obtained both through the leaves and the roots [49]. Atmospheric lead was found not to accumulate in the edible portions of most plants, with strawberries and leaf lettuce being notable exceptions [61, 69]. The amount of lead absorbed through the roots of plants located near highways was found to be insignificant in the edible portions of plants. 

---