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

Beryllium
185. It is generally believed that there are two phases – one rapid, one slow
– of beryllium removal from lungs, probably corresponding to the
removal of soluble and insoluble components respectively. In animal
models the half-life for rapid removal is between 1-60 days, while for
the slow phase it is in the range of 0.6-2.3 years (WHO/IPCS, 2001).
Rosenman et al. (2005) found that exposed workers without chronic
beryllium disease had been exposed to higher concentrations of
soluble beryllium – and thus had had a lower retained body burden –
than those with disease.
4.2.2 Distribution
186. Beryllium that is absorbed after inhalation is transferred to tracheal
lymph nodes and ultimately to the skeleton, the main site for storage
(WHO/IPCMS, 2001). In a rodent model where rats were exposed by
inhalation to radioactively labelled beryllium in the form of soluble
salts, measurements after 408 hours exposure suggested that 92% of
the total body radioactivity was in excreta with 6.8% retained in the
skeleton. Small amounts are transferred to the liver and other organs
(ASTDR, 2002). Beryllium may bind to the iron-transport protein
ferritin and be transported back to the lung where it can be taken up
by lung macrophages so promoting beryllium-antigen formation
(Sawyer et al., 2004); it is postulated that this action is the cause of
chronic beryllium disease many years after exposure has ceased.
187. Beryllium can form complexes with both adenosine triphosphate
(ATP) and adenosine diphosphate (ADP) (Boukhalfa et al., 2004),
as well as with endogenous proteins such as ferritin and transferrin
(Price and Joshi, 1983; Sawyer et al., 2004). Sawyer et al. (2002)
quote literature data suggesting that beryllium interacts with nuclear
acidic proteins, G proteins and protein kinases and interferes with
protein phosphorylation; in addition it inhibits the activities of
regulatory enzymes.
4.2.3 Metabolism
188. Beryllium and its compounds seem not to be biotransformed,
although it is likely that soluble salts can in part be converted to
insoluble forms in the lung (Reeves and Vorwald, 1967).
4.2.4 Elimination
189. Almost all (98%) ingested beryllium is excreted via faeces; much
inhaled low-solubility beryllium is transferred from the lung to the
gastrointestinal tract and similarly excreted. Renal excretion also
occurs after inhalation and is probably important for soluble
beryllium, and that solubilised in the lung; workers exposed to elevated
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