Establishing and explaining a baseline of octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) in end-exhaled air and urine.

Humans are regularly exposed to different consumer products that contain
siloxanes. Siloxanes make up a class of synthetic silicon-containing compounds
characterized by alternating atoms of silicon and oxygen. Exposure to
octamethylcyclotetrasiloxane (D4) or decamethylcyclopentasiloxane (D5) occurs
daily in 200 million individuals in the general population and hundreds of
individuals in the workplace.

Baseline concentrations in end-exhaled air and urine from daily exposure to
octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5), due to
use of personal care products (PCPs), has not been established as far as we
know. This study will give information about the dermal absorption of D4/D5 by
use of PCPs.

Biomonitoring of healthy volunteers in order to establish a baseline for D4 or
D5 exposure in the general population and response to dermal exposure in an
experiment under controlled exposure conditions.

Observational exposure study

The volunteers will be exposed to:
- 2 g pure substance D4
- 2 g pure substance D5
- a crème containing D4 or D5
- a deodorant containing D4 or D5
- a crème + deodorant containing D4 or D5

The study subjects will be asked to refrain from using personal care products
for 24 hours. They will be exposed to D4 as a pure substance, D5 as a pure
substance, a deodorant containing D4 or D5, a skin crème containing D4 or D5
and a combination of deodorant + crème. The administered dose will be in the
same range as occuring in normal daily use by consumers. Adverse events are
therefore not expected.
For the exposures and the measurements the study subjects will have to visit
the laboratory. First, will visit to give one urine sample and an end-exhaled
air sample in triplicate, to create a baseline. This will take approximately
half a hour. After that the exposure studies will take place, for which the
study subjects will have to come to the laboratory five times for approximately
8 hours per time. During these 8 hours end-exhaled samples will be collected in
triplicate, which leads to a total number of 51 samples. At the same time urine
samples will be collected in those 8 hours. The number of samples will depend
on the study subject, but be approximately between 4 and 6 samples. The study
subjects will also be asked to complete a questionnaire, to describe conditions
of the use of personal care products. To get a detailed overview of the use of
personal care products, the study subjects will be asked to complete a 24 hour
diary.
If the concentration of D4 or D5 in the end-exhaled air samples are much higher
than the concentrations in end-exhaled air samples from other study subject,
the involved study subject will be contacted to provide a buccal smear sample
for genotyping. This procedure will be discussed with the study subjects, prior
to the start of the experiments.