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Metabolic data for magnesium
REPORT OF COMMITTEE 2
METABOLIC
DATA FOR MAGNESIUM 1. Metabolism
Data from Reference Man (ICRP, 1975) Magnesium content of the body of soft tissue of the skeleton Daily intake in food and fluids
19g 7.8 g 11 g 0.34 g
2. Metabolic Model (a) Uptake to blood The fractional gastrointestinal absorption of dietary forms of magnesium is typically 0.2-0.7 (Wacker and Vallee, 1962; Shils, 1973; Schwartz, Spencer and Wentworth, 1978). Recent studies have shown that almost all this variation can be attributed to different levels of magnesium in the diet. Absorption varies from 0.70f0.11 for ingestion of 0.3 mmol of magnesium to 0.14+_0.04 for ingestion of 41.7 mmol (Roth and Werner, 1979). In this reportf, is taken to be 0.5 for all compounds of magnesium. (b) Inhalation classes The ICRP Task Group on Lung Dynamics (1966) assigned oxides, hydroxides, carbides, halides and nitrates of magnesium to inhalation class W and all other compounds of the element to inhalation class D. In the absence of any relevant experimental data this classification is adopted here. Inhalation class
fi
D W Y
0.5 0.5 -
(c) Distribution and retention
Stable magnesium is known to be concentrated in mineral bone (Wacker and Vallee, 1962; ICRP, 1975), this tissue being thought to act as a long-term reservoir for soft tissue requirements during deficiency (Wacker and Vallee, 1962). Studies in man (Silver et al., 1960; Yun et al., 1966; Roessler, 1972) indicate components of retention of magnesium in man with biological half-lives of between 0.25 and 35 days. However, long-term retention probably depends on the level of stable magnesium in the diet (Shils, 1973). In this report it is assumed that of magnesium leaving the transfer compartment 0.2 goes directly to excretion, 0.4 to mineral bone and 0.4 is distributed uniformly throughout all other organs and tissues of the body. Magnesium translocated to any organ or tissue of the body including mineral bone is assumed to be retained there with a biological half-life of 100 days.
11
LIMITS FOR INTAKES OF RADIONUCLIDES BY WORKERS
3. Clas&kation of Isotopes for Bone Dosimetry Since none of the isotopes of magnesium considered in this report has a radioactive half-lifeof more than 1 day it is appropriate to assume that magnesium is uniformly distributed over the surfaces of mineral bone at all times following its deposition in that tissue. References ICRP Task Group on Lung Dynamics (1966). Deposition and retention models for internal dosimetry of the human respiratory tract. Healrh Phys. 12, 173-207. ICRP Publication 23. Report of the Task Group on Reference Man. Pergamon Press, Oxford, 1975. Roessler, G. M. S. (1972). Whole-body retention and excretion of magnesium in humans, Ph.D. Thesis, University of Florida, University Microfilms Order No. 73965. Roth, P. and Werner, E. (1979). Intestinal absorption of magnesium in man. ht. J. Appl. Radial. Isotopes 30,523-526. Schwartz, R., Spencer, H. and Wentworth, R. A. (1978). Measurement of magnesium absorption in man using stable 26Mg as a tracer. Clin. Chim. Acta 87, 265-273. Shils, M. E. Magnesium. In: Modern Nutrition in Health and Disease-Dietotherapy, 5th edn, Part B, Chap. 6 (eds. Goodhart, R. S. and Shils, M. E.). Lea and Febiger, Philadelphia, 1973. Silver, L., Robertson, J. S., Dahl, L. K., Heine, M. and Tassinari, L. (1960). Magnesium turnover in the human studied with *sMg. J. Clin. Invest. 39, 420-425. Wacker, W. E. C. and Vallee, B. L. Magnesium. In: Mineral Metabolism, Vol. II, Part A, Chap. 22, pp. 483521 (eds. Conuu, C. L. and Bronner, F.). /.cademic Press, New York and London, 1962. Yun, T. K., Lazzara, R., Black, W. C., Walsh, J. J. and Burch, G. E. (1966). The turnover of magnesium in control subjects and in patients with idiopathic cardiomyopathy and congestive heart failure studied with magnesium-28. J. Nucl. Med. 7, 177-187.
Annual limits on intake, ALI
and derived air concentrations, isotopes of magnesium
DAC(Bq rnm3) (40 h wk) for
Inhalation Oral Radionuclide 2SMg
fi,=5X 10-l AL1 DAC
2 x 10’ -
Class D j,=5x
10-r
6x 10’ 3x lo4
Class W f,=5xlO_’ 5 x 10’ 2x lo*
METABOLIC
DATA FOR MAGNESIUM 1. Metabolism
Data from Reference Man (ICRP, 1975) Magnesium content of the body of soft tissue of the skeleton Daily intake in food and fluids
19g 7.8 g 11 g 0.34 g
2. Metabolic Model (a) Uptake to blood The fractional gastrointestinal absorption of dietary forms of magnesium is typically 0.2-0.7 (Wacker and Vallee, 1962; Shils, 1973; Schwartz, Spencer and Wentworth, 1978). Recent studies have shown that almost all this variation can be attributed to different levels of magnesium in the diet. Absorption varies from 0.70f0.11 for ingestion of 0.3 mmol of magnesium to 0.14+_0.04 for ingestion of 41.7 mmol (Roth and Werner, 1979). In this reportf, is taken to be 0.5 for all compounds of magnesium. (b) Inhalation classes The ICRP Task Group on Lung Dynamics (1966) assigned oxides, hydroxides, carbides, halides and nitrates of magnesium to inhalation class W and all other compounds of the element to inhalation class D. In the absence of any relevant experimental data this classification is adopted here. Inhalation class
fi
D W Y
0.5 0.5 -
(c) Distribution and retention
Stable magnesium is known to be concentrated in mineral bone (Wacker and Vallee, 1962; ICRP, 1975), this tissue being thought to act as a long-term reservoir for soft tissue requirements during deficiency (Wacker and Vallee, 1962). Studies in man (Silver et al., 1960; Yun et al., 1966; Roessler, 1972) indicate components of retention of magnesium in man with biological half-lives of between 0.25 and 35 days. However, long-term retention probably depends on the level of stable magnesium in the diet (Shils, 1973). In this report it is assumed that of magnesium leaving the transfer compartment 0.2 goes directly to excretion, 0.4 to mineral bone and 0.4 is distributed uniformly throughout all other organs and tissues of the body. Magnesium translocated to any organ or tissue of the body including mineral bone is assumed to be retained there with a biological half-life of 100 days.
11
LIMITS FOR INTAKES OF RADIONUCLIDES BY WORKERS
3. Clas&kation of Isotopes for Bone Dosimetry Since none of the isotopes of magnesium considered in this report has a radioactive half-lifeof more than 1 day it is appropriate to assume that magnesium is uniformly distributed over the surfaces of mineral bone at all times following its deposition in that tissue. References ICRP Task Group on Lung Dynamics (1966). Deposition and retention models for internal dosimetry of the human respiratory tract. Healrh Phys. 12, 173-207. ICRP Publication 23. Report of the Task Group on Reference Man. Pergamon Press, Oxford, 1975. Roessler, G. M. S. (1972). Whole-body retention and excretion of magnesium in humans, Ph.D. Thesis, University of Florida, University Microfilms Order No. 73965. Roth, P. and Werner, E. (1979). Intestinal absorption of magnesium in man. ht. J. Appl. Radial. Isotopes 30,523-526. Schwartz, R., Spencer, H. and Wentworth, R. A. (1978). Measurement of magnesium absorption in man using stable 26Mg as a tracer. Clin. Chim. Acta 87, 265-273. Shils, M. E. Magnesium. In: Modern Nutrition in Health and Disease-Dietotherapy, 5th edn, Part B, Chap. 6 (eds. Goodhart, R. S. and Shils, M. E.). Lea and Febiger, Philadelphia, 1973. Silver, L., Robertson, J. S., Dahl, L. K., Heine, M. and Tassinari, L. (1960). Magnesium turnover in the human studied with *sMg. J. Clin. Invest. 39, 420-425. Wacker, W. E. C. and Vallee, B. L. Magnesium. In: Mineral Metabolism, Vol. II, Part A, Chap. 22, pp. 483521 (eds. Conuu, C. L. and Bronner, F.). /.cademic Press, New York and London, 1962. Yun, T. K., Lazzara, R., Black, W. C., Walsh, J. J. and Burch, G. E. (1966). The turnover of magnesium in control subjects and in patients with idiopathic cardiomyopathy and congestive heart failure studied with magnesium-28. J. Nucl. Med. 7, 177-187.
Annual limits on intake, ALI
and derived air concentrations, isotopes of magnesium
DAC(Bq rnm3) (40 h wk) for
Inhalation Oral Radionuclide 2SMg
fi,=5X 10-l AL1 DAC
2 x 10’ -
Class D j,=5x
10-r
6x 10’ 3x lo4
Class W f,=5xlO_’ 5 x 10’ 2x lo*