Benzene is a volatile organic compound (VOC) on the State of California's "Prop 65" list of known chemical carcinogens. Benzene is a neurotoxin and can be found at low detections in ambient air.

Signs of benzene exposure can be dizziness, headaches, nausea, irritation to eyes and mucous membranes. Benzene is a constituent of crude oil and is associated to refinery emissions, petroleum product storage, vehicle tailpipe emissions, gas stations, other industrial emission sources, solvents, woodsmoke, tobacco smoking tobacco and cigarette smoke.

Long-term exposures to airborne benzene can be a cause of blood cancers and developmental/reproductive problems. Acute benzene poisoning can lead to heart arrhythmias, respiratory tract inflammation, pulmonary blood clots and hemorrhages, and affect kidneys and brain function.

When inhaled, particles of soot (such as from tailpipe emissions and burning charcoal), may lead to increased breathing difficulty and asthma attacks, and affect heart and circulatory system functions, including blood pressure/hypertension. Repeated exposures may require emergency room visits (Scientists have not yet concluded how black carbon affects health).

Depending on the level of exposure, ozone can make lungs more susceptible to infection and aggravate lung diseases such as asthma, emphysema, and chronic bronchitis. Ozone can increase the frequency of asthma attacks. Ozone can cause coughing, a sore or scratchy throat, make it difficult to breathe deeply, and inflame and damage the airways.

Tiniest, invisible particles, at 2.5 microns or less (“PM2.5”) are most dangerous for health. PM2.5 can't be expelled by coughing, because the particulates travel deep into the lungs, lodging in tissues and releasing into the bloodstream other air toxins attached to them. Chronic exposure to PM2.5 can lead to blood clots, stroke and heart attacks. People with compromised immune systems may be more susceptible to viruses and bacterial infections, which can lead to pneumonia in children and older people.

Short term exposure can cause lung problems, burning of nose and throat. Longer term effects of chronic exposures are decreased lung function and chronic asthma.

Short term exposure can cause eye and nose irritation, confusion, headaches, anxiety, dizziness, and insomnia. More serious effects from chronic exposures may include kidney and liver damage, and possibly infertility.

Exposure for any amount of time can cause headaches, lack of coordination, confusion and dizziness. Exposure to high concentrations can cause skin, eye, nose, throat irritation, lung problems, breathing difficulty, memory loss, liver and kidney changes.

PM10 includes dust from construction sites, landfills and agriculture, wildfires and brush/waste burning, industrial sources, wind-blown dust from open lands, pollen and fragments of bacteria.

Short-term exposures to PM10 have been associated primarily with worsening of respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD), leading to hospitalization and emergency department visits.

Hydrogen sulfide can usually be smelled at low levels of concentration with immediate symptoms such as burning eyes, coughing, fatigue, and shortness of breath. At moderate levels of concentration, exposure can cause severe eye and respiratory irritation, including fluid in the lungs, nausea and staggering. The results of exposure to high levels of concentration can be life threatening with effects such as the inability to breathe, convulsions, unconsciousness, coma, and death.

As prolonged exposure may result in the inability to distinguish the odor at all, measuring levels of concentration is invaluable in providing early detection to mitigate long-term health effects.