Guidelines for Metals and Metalloids in Ambient ... - ARCHIVE: Defra

Arsenic
2.2.3 Tissue distribution and excretion
71. Most forms of inhaled arsenic are excreted within a few days via the
kidney as MMA and DMA. Urinary excretion accounts for 30 – 60% of
the inhaled dose (Vahter, 1986). Since the deposition fraction of an
inhaled dose ranges from 30 – 60% for most respirable particulate
matter, this suggests that nearly all arsenic that is deposited in the lung
is excreted in the urine. The relative proportions of arsenic, MMA, and
DMA in urine vary depending upon the chemical administered, the time
after exposure, the route of exposure, the dose level, and the exposed
species of animal. Increased MMA/DMA ratios have also been
observed in mice, but only at much higher doses (Hughes et al., 1994).
72. Several pharmacokinetic models have been developed for evaluating
the kinetic behaviour of arsenic (Clewell et al., 1999). However they
focus on the prediction of the urinary elimination of arsenic species
under different exposure conditions, rather than estimation of arsenic
species concentrations in the various target tissues associated with
arsenic’s adverse effects.
73. Although no studies on the distribution of organic arsenic in animals
after inhalation exposure were identified, DMA administered to rats
via the trachea was distributed throughout the body suggesting that
inhalation of organic arsenic compounds also leads to widespread
distribution. Where excretion of organic arsenic compounds is
concerned it appears to be prompt, rats exposed to DMA via the
trachea excreted 60% in the urine and about 8% in the faeces within
24 hours (Stevens et al., 1977).
2.3 Health effects
2.3.1 Acute effects
2.3.1.1 Animals
74. Aqueous solutions of arsenic are ten times more toxic than arsenic
administered dry by the same route. Rats appear more susceptible to
arsenic in solution than mice of a similar age, although no difference
in acute toxicity was found between males and females of the same
species. There are, however, considerable differences in arsenic toxicity
among different strains of mice. Following acute administration
marked haemorrhage of the stomach and intestine has been reported
(Satterlee, 1958) as well as fatty degeneration of the liver with cell
necrosis and reparative changes (Rossing, 1941). No reports have been
found showing that metallic arsenic has appreciable acute toxicity.
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