The primary hypothesis of the study is that in healthy elderly subjects experimental exposure to air pollutants increases sympathetic nervous system activity compared with sham (clean air) exposure. The secondary hypothesis of the study is that combined experimental exposure to air pollutants (particles + ozone) increases sympathetic nervous system activity to a greater extent than does the exposure to particles alone.

In a randomized, double-blind, and cross-over fashion, the participants will be exposed to clean air, ultrafine particles, or ultrafine particles and ozone in an exposure chamber. The investigators will determine blood pressure, heart rate, respiration as well as cardiac output and directly record sympathetic vasomotor tone using the microneurography technique. To elucidate the underlying mechanisms through which particles and ozone affect the autonomic nervous system, the investigators will assess the local and systemic inflammatory response as well as the changes in neurotrophic factors in sputum and blood. In addition, the activation of inflammatory cells in sputum and blood will be analyzed at different points in time after exposures. Changes in sympathetic activity will be correlated with the degree of airway inflammation and oxidative stress assessed in induced sputum and blood. This study will provide important insight in the mechanisms through which air pollution, particularly ultrafine particle exposure, increases cardiovascular risk in human subjects and generate a human model for mechanistic and therapeutic studies.

Inclusion Criteria:

• Elderly man or postmenopausal woman older than 50 years of age.
• Signed written informed consent.

Exclusion Criteria:

• Smoker.
• Cardiovascular and/or pulmonary disease.
• Medication with relevant impact on autonomic system function, e. g. norepinephrine reuptake inhibitors. Stable medication with slight to moderate autonomic effects is tolerable.
• Subject is the investigator or any sub-investigator, research assistant, pharmacist, study coordinator, other staff or relative thereof directly involved in the conduct of the protocol.
• Mental condition rendering the subject unable to understand the nature, scope, and possible consequences of the study.
• Subject unlikely to comply with protocol, e. g. uncooperative attitude or unlikelihood of completing the study.
• Known hypersensitivity to ozone.
• History of drug or alcohol abuse. Particles Study - Protocol version: October 19, 2012 14
• Blood donation of more than 500 mL during the previous 3 months.