Aluminum zirconium chloride hydroxide

Endpoint summary

Description of key information

"Aluminium":
Absorption rate - oral: 1%
Absorption rate - dermal: 1%
Absorption rate - inhalation: 2%
"Zirconium":
Absorption rate - oral: 1%
Absorption rate - dermal: 1%
Absorption rate - inhalation: 2%

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

1

Absorption rate - dermal (%):

1

Absorption rate - inhalation (%):

2

Additional information

Aluminium

Aluminium is poorly absorbed following either oral or inhalation exposure and is essentially not absorbed dermally. Approximately 0.1–0.6% of ingested aluminium is usually absorbed, although absorption of less bioavailable forms, such as aluminium hydroxide, can be on the order of 0.1%.The main mechanism of absorption is probably passive diffusion through paracellular pathways. Aluminium binds to various ligands in the blood and distributes to every organ, with highest concentrations found in bone and lung tissues. Absorbed aluminium is excreted principally in the urine and, to a lesser extent, in the bile; unabsorbed aluminium is excreted via faeces. Only under certain atypical conditions such as renal dysfunction with concurrent high aluminium intakes, can levels of aluminium in the body rise high enough to cause toxicity in humans; the main target organs under these conditions appear to be the central nervous system and bone (source: ATSDR, 2008).

Oral absorption: based on the above, a conservative default oral absorption of 1% will be assumed for risk assessment purposes.

Dermal absorption of aluminium (test substance: aluminium chlorohydrate) has been shown experimentally to be very low with approx. 0.1-0.2% (Flarend, 2001). In the absence of substance-specific data, the HERAG default value of 1% will be assumed as a conservative assumption for risk assessment purposes.

Inhalation absorption: the percentage of aluminium absorbed following inhalation exposure was not reported in occupational toxicokinetic studies, but a fractional absorption of 1.5–2% was estimated based on the relationship between urinary aluminium excretion and the airborne soluble aluminium to which workers were exposed (Yokel and McNamara 2001, cited in ATSDR, 2008). Given that systemic absorption of airborne aluminium occurs partly via the lungs but also partly via the gastrointestinal tract after mucociliary clearance from the respiratory tract, the above stated value of 2% will be taken forward for risk assessment purposes.

 

Zirconium

Data on toxicokinetics of zirconium in the public domain are sparse. Nevertheless, the following conclusions are useful for orientating risk assessment purposes:

Oral absorption: in a study with rats, the maximal uptake of various zirconium compounds from the gastrointestinal tract was found to be 0.2 % of the elemental zirconium dose (Fletcher 1969). In another study, the uptake of only 0.001 % of the zirconium dose (ZrCl4) from the gastrointestinal tract into the bloodstream was demonstrated (Clayton and Clayton 1981, cited in MAK, 1999) Based on the above, a conservative default oral absorption of 1% will be assumed for risk assessment purposes.

Dermal absorption: in the absence of substance-specific data, the HERAG default value of 1% will be assumed as a conservative assumption for risk assessment purposes.

Inhalation absorption: data specifically for zirconium absorption form the lungs are not available. However, in view of the similarly low systemic availability of zirconium when compared to aluminium (estimated inhalation absorption 1.5–2%), the reasonable assumption that systemic absorption will occur via lungs and also gastrointestinal tract after mucociliary clearance and any inhalation exposure to “aluminium zirconium chloride hydrate” will intrinsically yield the same deposition pattern in the respiratory tract, the above stated value of 2% is also considered appropriate to be taken forward for risk assessment purposes of zirconium.

 

References

ATSDR, 2008: Agency for Toxic Substances and Disease Registry (ATSDR). 2008. Toxicological profile for Aluminum. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service.

Clayton and Clayton, 1981 (Ed.): The metals (Chapter authored by Stockinger, E.). In: Patty's industrial hygiene and toxicology. New York, NY: John Wiley Sons, 1493-1505.

Flarend, 2001: A preliminary study of the dermal absorption of aluminum from antiperspirants using aluminum-26. Food Chem Toxicol 39(2):163-168.

Fletcher,1969: The radiological hazards of zirconium-95 and niobium-95. Health Phys16:209–220

MAK, 1999: Zirconium and its compounds [MAK Value Documentation, 1999]. The MAK Collection for Occupational Health and Safety. 224–236.

HERAG: Health Risk Assessment Guidance for Metals. Fact Sheet 01: Assessment of occupational dermal exposure and dermal absorption for metals and inorganic metal compounds. http://www.icmm.com/page/1213/health-risk-assessment-guidance-for-metals-herag [link accessed 2013-02-05]

Yokel and McNamara, 2001: Aluminium Toxicokinetics: An Updated MiniReview. Pharmacology & Toxicology 2001, 88, 159-167