The effects of nanoparticles and ambient particles on brain function using quantitative electro-encephalography (QEEG) in healthy volunteers

Particulate matter (PM) is a complex mixture of different particle types, much
of which are unlikely to cause any adverse effects and so the hypothesis has
arisen that a subcomponent(s) of PM drives the adverse effects. Combustion has
been recognized as an important source of particle imission (Avakian et al,
2002) and several epidemiological studies have been able to identify
combustion-derived particles as an important component in driving adverse
effects of PM (Pope et al, 1999; Laden et al, 1999). In addition there is now
a considerable amount of toxicological research demonstrating the toxicity of
combustion-derived particles that are below 100 nm size, and accordingly
denominated as combustion-derived nanoparticles (CDNP). Combustion is
ubiquitous in the modern world and the generation of CDNP is correspondingly
omnipresent. Much research emphasis has been placed on traffic derived CDNP in
PM such as diesel exhaust particles (DEP), which are the source of most CDNP in
our cities where the greatest potential for human exposure exists (Donaldson et
al, 2005). A considerable amount of research has demonstrated the toxicity of
CDNP such as diesel soot (e.g. Diaz-Sanchez & Riedl, 2005;Sydbom et al, 2001),
welding fumes (Antonini et al, 2004) or fly-ashes (Borm, 1997; Ghio, 2004), and
the molecular toxicology of these materials include a common pathway such as
oxidative stress mediated inflammation, which is considered to be crucial in
both pulmonary and systemic effects of environmental PM exposure (Donaldson et
al, 2003). These effects include increased mortality and morbidity in patients
with COPD, asthma, cardiovascular disease or diabetes (Pope et al, 2004)
A relative new finding is the fact that nanoparticles are able to translocate
to the brain after deposition in the nose(Oberdorster et al, 2004) and maybe
are associated to inflammatory changes at sites of deposition (Campbell et al,
2005). The passage to the brain is of particular concern since nanoparticles
are active in causing oxidative stress (Nel et al, 2006; Donaldson et al, 2005)
and the brain is very sensitive to damage caused by oxidative stress
(Halliwell, 2006) . Oxidative stress has been implicated in the pathogenesis of
neurodegenerative diseases such as Parkinson*s and Alzheimer*s disease. It is
conceivable that the long term effects might include a decrease in cognitive
function. Evidence for such effects is presented by studies in biopsies from
city dwellers and Alzheimer's like pathology has been demonstrated through
increased markers of inflammation and AB42-accumulation in frontal cortex and
hippocampus in association with the presence of Nanoparticles (Calderon et al,
2004). Recently, also inhalation exposure of BALB/c mice to with particulate
matter showed that activation of pro-inflammatory cytokines in the brain of
exposed mice (Campbell et al, 2005).

To investigate whether exposure to nanoparticles is able to induce short-term
functional changes in the brain, we previously exposed human volunteers for one
hour to diesel exhaust particulates (300 ug/m3) and followed their brain
activity during exposure and up to one hour after exposure.
The aims of the current study are:
• To investigate the response in QEEG in response to different concentrations
and times (product is dose) of spark generated carbon nanoparticles as a source
of pure, uncontaminated nanoparticles.
• To investigate changes and regulation of microcirculation in subjects exposed
to real life PM by exposing them to concentrated nanoparticles, diesel exhaust
and concentrated air particles (CAPS) on different days and comparison to
clean, filtered air.
• To investigate whether systemic oxidative stress is associated to particulate
exposure and or changes in microcirculation.

This is a cohort study with double blind randomized controlled cross-over
design. Twenty non-smoking volunteers with normal lung function and no history
of respiratory disease will be invited to attend on three separate days at
least two weeks apart and receive a double-blind randomized cross-over exposure
to filtered clean air, *pure* carbon particles and concencrated ambient air
particles (CAPs). Each subject will be exposed for 1 hour in the special mobile
laboratory equipped with a body box. During and after exposure, subjects will
remain in the body box and their QEEG and will be followed up to 1 hour
post-exposure. EEG and CO-exhalation will be continuously recorded during both
hours while subjects are sitting in an upright position.
Previous to and after exposure in the body-box the following measurements will
be done:
- resting brain activity outside the exposure chamber in a 3-minute eyes
open and 3-minute eyes closed condition.
- Measurement of finger blood-flow with laser-doppler
- a spot sample of urine needs to be collected and frozen.

Exposure (1 hour) to carbon naoparticles at a concentration of 40 and 80 ug/m3
or to diesel particles (150 ug/m3) and CAPS (150-300 ug/m3) at different
occasions.

The burden of separate outcome measures is without significant discomfort or
risk. The major discomfort will be caused by sitting 2 hours in a body-box.