Particulate Matter, Blood Pressure, and the Sympathetic Nervous System

Inclusion Criteria: * 1\. Age 18-65 years old. People older than 65 years are excluded as the impact of PM2.5 on their BP is not known from our prior studies (which included younger individuals) and they have age-related increases in BP and SNS activity which may alter their associations with PM2.5 exposures and thus produce too heterogeneous a population to evaluate the linkages between PM2.5 and health outcomes. * 2\. Self-reported nonsmoker (100% abstinence for at least 1 year) living in non-smoking households (no one living in the household that smokes indoors) and no known routine exposures to air pollutants by known point sources at home, travel or occupationally (e.g., fumes, dust, secondhand smoke). Smoking and other exposures may alter any effect that ambient PM2.5 has on the health outcomes. * 3\. Able to understand the informed consent, legally provide informed consent, and able to participate for the entire duration of the study. Exclusion Criteria: * 1\. Any facial hair (beard or mustache) that does not allow for proper fitting and air tight seal of the N95 facemask during the study that would compromise the ability of the mask to prevent exposures. * 2\. Any prior cardiovascular diseases (coronary artery disease (CAD), congestive heart failure (CHF), stroke, peripheral arterial disease (PAD), aneurysms, any revascularization)\* * 3\. Prior diagnosis of hypertension, diabetes, sleep apnea\* * 4\. Prior diagnosis of chronic lung diseases (asthma, chronic obstructive lung disease (COPD))\* * 5\. Prior diagnosis of neurological disorders (Parkinson's disease, autonomic failure, peripheral neuropathy, seizure disorder) or other conditions at discretion of investigators\* * 6\. Prior diagnosis of chronic kidney disease, any type of dialysis\* * 7\. Active or history of any known cancer\* * 8\. History of HIV\* * 9\. Being treated for any infection with antibiotics within past month\* * 10\. Mental health issue(s) including anxiety disorders, mood disorders, schizophrenia, or other conditions at discretion of investigators\* * 11\. Prior diagnosis of any other chronic or acute medical condition(s) at discretion of investigators that may lead to alteration of baseline SNS activity, BP, or insulin sensitivity and thereby potentially impact the association of PM2.5 with study outcomes. * 12\. Medications for high BP or that alter BP. Any medications for cholesterol (e.g., statins). Any medications that alter blood glucose (e.g., diabetes medication)\*. * 13\. Any medications or over the counter pills that may alter the association between ambient PM2.5 and the health outcomes of BP, SNS activity and insulin sensitivity by discretion of investigators\*. No over the counter pills taken on routine basis (\>2 times per week as standing dosage) including: anti-oxidants (vitamin C, E), NSAIDS, fish oil supplements, folic acid supplements, multivitamins, or other over the counter pills, herbs, or complimentary therapies under the discretion of the investigators. These pills can be stopped for 3 months on an elective basis and then the individual can enter the study. Other medications for chronic stable conditions that are not listed in exclusion criteria and that are not likely to influence the study results can be taken or continued as long as their doses have been stable for 3 months prior to entering the study. Estrogen or birth control can be used (any type) as long as the dosing has been stable for past 3 months. Medications or over the counter drugs used on an as needed basis (such as Tylenol or aspirin) are fine as long as not routinely taken \>2 times per week)\* Planned major change in lifestyle including work, activity, exercise, diet, weight during course of study\* * 14\. Screening visit BP ≥140/90 mm Hg (as measured by the automated office BP device- BpTru) * 15\. Screening visit arm circumference ≥17 inches (makes home BP monitoring inaccurate as the cuff of the commercially-available devices will not fit). * 16\. Screening visit pregnancy (positive urine pregnancy test in women \<50 years of age) and any plan to become pregnant during the study period