The Interaction of Social Factors With Air Pollution
Condition: Exposure to Environmental Pollution, Non-occupational
Study type: Interventional

Summary: 
      Purpose:

      The purpose of this protocol is to understand how social factors such as psychosocial stress
      may modify how people respond to air pollution. Ultimately this will help us understand
      health disparities from poor air quality.

      Participants:

      Up to 40 healthy adults,18-33 years old with different perception of stress will participate
      and complete this study.

      Procedures (methods):

      Subjects will be exposed to clean air and to ozone ( 300ppb) for 2 hours in a controlled
      environment chamber. Cardiac, vascular, pulmonary and cognitive function will be evaluated
      pre, immediately post and 18 hr post exposure.

      The primary endpoint will be Heart Rate Variability . Secondary endpoints will include
      pulmonary function, analysis of blood clotting/coagulation factors, biomarkers of stress,
      cognitive function, radial artery pulse wave measurements and analysis of soluble factors
      present in plasma.
    

Detailed description: 
      Over the past decades, air quality in the U.S. has improved significantly. Even so, millions
      of people in the U.S. still live in counties that do not meet air quality standards for one
      or more pollutants. Ozone is a major component of photochemical smog and is one of the most
      thoroughly studied gaseous pollutants. Controlled human exposure studies have been critical
      in demonstrating that it can cause airway inflammation 1-3, including increases in neutrophil
      infiltration into the lung and the production of pro-inflammatory mediators 4,5[, and
      ultimately decrements in lung function [reviewed in 6]. More recent studies have shown that
      ozone can also increase vascular inflammation, as well as alter autonomic nervous system
      control of heart rate and cardiac repolarization 7. Numerous epidemiological studies have
      also demonstrated an association between acute and chronic exposure to ambient levels of
      ozone and various health effects most notably asthma 6. These studies have also highlighted a
      need to incorporate social and nonchemical factors into risk assessments 8. Similarly, social
      factors such as psychological stress are now regarded as important contributors to asthma
      outcomes 9,10. This protocol is aimed at investigating how stress impacts health responses to
      air pollutants. Since psychosocial stress-related susceptibility has been proposed to explain
      social disparities, this will help us understand which populations and individuals are at
      increased risk from air pollution.

      This protocol is designed to determine whether nonchemical stressors exacerbate ozone
      effects. In particular we will focus on elevated psychosocial stress as it has been shown to
      contribute to several adverse health outcomes, most notably, to cardiovascular disease. The
      physiological mechanism by which psychosocial stress leads to health effects is due, at least
      in part, to elevated circulating glucocorticoids, or stress hormones, which are regulated by
      the hypothalamic-pituitary-adrenal (HPA). In the last 30 years the concept of allostasis has
      evolved. Allostasis is the process whereby an organism adapts to the demands of the
      environment. An allostatic load model applies this concept to chronic stress11. In this model
      the perception of threat over long time intervals (perceived stress) can cause
      over-activation of the HPA-axis resulting in changes in physiological systems as chemical
      imbalances in autonomic nervous system, central nervous system, neuroendocrine, and immune
      system activity. Factors such as genetics, behavior, life events and diet can impact this
      model. To our knowledge no clinical study has investigated the link between air pollution
      effects on cardiovascular disease and psychosocial stress. However, several studies have now
      shown an association between stress and respiratory outcomes to air pollution. Claugherty and
      colleagues (2007) found an association between traffic-related air pollution and asthma
      solely among children exposed to violence 12. Shankardass and colleagues demonstrated that
      children from stressful households are more susceptible to the effects of traffic-related
      pollution on the development of asthma 13. In that study, stress was evaluated using the
      Perceived Stress Scale (PSS) developed by Dr. Sheldon Cohen of Carnegie Mellon University.
      This is the most widely used psychological instrument for measuring the perception of stress
      and has been validated in multiple studies. We will use this scale to evaluate the degree to
      which subjects appraise situations in their life as stressful. Heart rate variability (HRV)
      is considered to be a reliable biomarker of stress. Chronic stress has been shown to be
      associated with decreases in HRV 14. Since acute ozone exposure can also cause changes in
      HRV, we have chosen HRV as our primary endpoint. We hypothesize that the imbalance between
      the sympathetic and the parasympathetic nervous system caused by chronic stress will result
      in altered responses to ozone exposure that will be reflected by HRV.
    

Intervention name(s): Clean Air; Ozone
Intervention type(s): Other; Other
Intervention description(s): Each subject will be exposed to clean air for 2 hours. Subjects will exercise on a bike or treadmill. Each exercise session will consist of a 15 minute exercise interval at a level of up to 25 L/min/m2BSA followed by a 15 minute rest period.; Each subject will be exposed up to 0.3ppm ozone for 2 hours. Subjects will exercise on a bike or treadmill. Each exercise session will consist of a 15 minute exercise interval at a level of up to 25 L/min/m2BSA followed by a 15 minute rest period.
Other intervention name(s): O3
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Basic Science
Keywords: Controlled Human exposure study; Air Pollution; Cardiovascular; Social factors; Cognitive function