Feldspar minerals, magnetite and quartz, calcination products of copper mining residues.

Endpoint summary

Description of key information

With regard to toxikokinetics (absorption, metabolism, distribution and elimination) of the pigment, the assessment and corresponding data are primarily based on data on magnetite and on lead. However, as stated in EPA (2003), in Kreamer (2004), Lide (2001) and elsewhere in scientific literature, iron oxides (such as magnetite and hematite) are virtually insoluble in water and the fact that iron is an essential element to humans and to mammals in general, renders it difficult to assess the toxicokinetic properties of the magnetite, while the toxicokinetics of lead is extensively assessed and described in scientific literature. Thus , the toxicokinetic properties of the pigment used for the risk assessment of the pigment is mainly the toxicokinetics of the lead even though this is probably a worst-case scenario. Extraction experiments of the actual pigment in physiologically relevant buffers mimicking the enzymatic composition of the stomach has hitherto failed to show any bioavailability for neither lead nor magnetite (PBET-extraction studies).

The extremely low bioavailability of lead in the pigment, observed in PBET-extraction studies is further corroborated by the data on lead in blood in occupationally exposed workers at the pigment and paint production site. At the site, lead in blood have been systematically monitored since 1990. The same workers both work in the pigment manufacture and in the formulation of the paint (paint production). The regular employees had worked at the factory for 2-10 years when the monitoring program started in 1990, and thus some of them has now (2017) worked at the site for 30-40 years.

For individual regular employees, levels of lead in blood have not increased during the monitoring period (1990-2016), and in some cases been in steady decline.

Iron exist as a redox couple F(II)/Fe(III) and at physiologically relevant pH all Fe(II) is oxidized to Fe(III), which isis virtually insoluble at physiological pH (K_{free Fe(III)}= 10^-18mol/l). The saturation concentration of Fe₃O₄in serum is 68.0-74.5 nmol/ml for a particle size of 0.45-5 µm (nanoparticles – microparticles). In addition, about 95% of the iron of magnetite is bound to plasma proteins mainly transferrin (Frenet, 1983).

Lead is most easily taken up into the body through inhalation or ingestion – dermal uptake makes a negligible contribution to systemic lead levels. Once taken up into the body, lead is not metabolized. However, lead will distribute to a variety of tissue compartments such as blood, bone and soft tissues. The half-life of lead in the body varies as a function of body compartment. Lead in blood has a half life of 30 – 45 days – measurement of lead in blood thus provides an integrated assessment of average lead exposure (via all routes) over the preceding month. Lead is retained far longer in bones. Depending upon bone type, the retention time of lead can vary between 8 and 30 years. Such lead can both serve as a source of endogenous lead exposure and as a cumulative index of exposure over a time frame of years. Lead excretion is primary via urinary and biliary excretion routes.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential