The Air Quality Index (AQI) is a numerical and color-coded system used to report how polluted the air is and what associated health effects may be a concern. It helps people, especially those with heart or lung conditions, decide when to limit outdoor activity. The index measures pollutants like ozone, particle pollution, carbon monoxide, sulfur dioxide, and nitrogen dioxide, and ranges from 0 to 99+.
AQI is measured by taking hourly readings of specific pollutants like PM2.5, PM10, CO, and NO₂, converting each concentration into a sub-index, and then using the highest sub-index value to determine the overall AQI. Each pollutant is measured in a specific unit (e.g., µg/m³) for particulate matter) and compared against breakpoints to convert it into a single AQI value, with the highest of these values being the final reported AQ.
Common sources of air pollution include human activities like vehicle and industrial emissions (from factories and power plants burning fossil fuels) and area sources such as agricultural activities, construction, and waste burning. Natural sources also contribute, including dust storms, wildfires, and volcanic eruptions.
Ideal air quality is considered "Good" (0-25 on the Air Quality Index or AQI), posing little to no risk to health. As the AQI increases, air quality becomes "Fair" (25.1-35), "Unhealthy for Sensitive Groups" (35.1-45), "Very Unhealthy" (45.1-55), "Acutely Unhealthy" (55.1-90), and finally "Hazardous" (90.1 and above), with each level posing progressively greater health risks, especially for sensitive groups.
Poor air quality affects human health by causing a range of issues, from respiratory illnesses like asthma and pneumonia to cardiovascular diseases, strokes, and lung cancer. Small particles can penetrate deep into the lungs and bloodstream, leading to irritation, inflammation, and systemic damage. Vulnerable populations such as children, the elderly, and those with pre-existing health conditions are disproportionately at risk.
Sound level is a logarithmic measurement of sound pressure, expressed in decibels (dB), that indicates how loud a sound is. It reflects the wide range of sound intensities the human ear can perceive, from the quietest audible sound ((0) dB) to the threshold of pain ((120)–(140) dB). For example, normal speech is around (60) dB, while a rock concert is about (120) dB.
Common noise sources range from a quiet room at 30 dB to loud concerts and sirens at 110–130 dB. Sounds like a normal conversation are around 60 dB, while a lawnmower or a power tool can be about 90–100 dB, and events like fireworks or jet engines can reach 140–160 dB or higher. Prolonged exposure to noises above 85 dB can cause hearing damage
Safe exposure limits vary depending on the substance and the context (e.g., workplace, emergency) and are defined by different organizations like OSHA, NIOSH, and ACGIH. Key terms include Time-Weighted Average (TWA), which is the average exposure over an 8-hour workday, and Short-Term Exposure Limit (STEL), a 15-minute limit that should not be exceeded more than four times a day. For emergencies, public guidelines like ERPGs (Emergency Response Planning Guidelines) are used, with different levels for no effects, no serious effects, and not life-threatening situations.
Air and noise pollution together can negatively affect wellbeing by amplifying stress responses, increasing inflammation, and disrupting sleep, which can lead to a greater risk of mental health issues like anxiety and depression, and physical health problems like cardiovascular disease and metabolic syndrome. The combined exposure creates a heightened "allostatic load," where the body's stress-coping systems are overwhelmed.
Both air and noise pollution are stressors that trigger the body's stress response system (e.g., the HPA axis and sympathetic nervous system). When combined, they can accelerate the progression to "allostatic overload," a state where the body's ability to cope is overwhelmed, increasing the risk of disease.
Air pollution induces a persistent, low-grade inflammatory state, while noise pollution can trigger similar inflammatory and oxidative stress responses. Their combined effects can worsen these processes, potentially exacerbating respiratory issues and systemic inflammation.
Studies show that co-exposure to air and noise pollution has stronger associations with negative health outcomes than exposure to either one alone. For example, one study found a stronger association between the combination of high noise and high (NO₂) and an increased risk of ischemic stroke.
• Anxiety and depression: Higher exposure to both air and noise pollution is linked to a greater risk of developing anxiety, depression, and other mental health issues. This is particularly concerning for young people during adolescence, a critical period for psychological development.
• Cognitive impairment: The combined effects can lead to cognitive impairment and distraction, impacting learning and overall cognitive function.
• Cardiovascular and metabolic issues: Co-exposure increases the risk of developing metabolic syndrome (MetS) and its components, such as high blood pressure, high triglycerides, and low HDL cholesterol. Chronic exposure to noise pollution alone is also linked to cardiovascular diseases like ischemic heart disease.
• Sleep disturbance: Sleep disturbance negatively impacts well-being by affecting mental and physical health, leading to issues like poor concentration, mood swings, and increased risk of chronic conditions such as heart disease and diabetes.
• Children and adolescents are particularly vulnerable. For example, aircraft noise has been linked to reading impairment in school children, and both air and noise pollution can have a greater impact on their developing nervous systems and mental wellbeing.
Environmental and urban impacts are the significant, often negative, environmental consequences of urbanization, including increased air and water pollution, habitat loss, and the urban heat island effect. These issues are driven by high population density, resource consumption, and waste generation, which are exacerbated by the concentration of people in cities and their contribution to climate change. Effective urban planning is crucial for mitigating these impacts by addressing issues like resource management, waste disposal, and the integration of green spaces.
• Sustainable urban planning: Implementing thoughtful urban planning is essential for managing growth, preserving natural resources, and protecting residents.
• Resource-efficient technologies: Using technologies that reduce energy consumption, manage waste more effectively, and improve the efficiency of water use can help mitigate environmental strain.
• Green infrastructure: Incorporating more green spaces, such as parks and trees, can help reduce the urban heat island effect, improve air quality, and manage stormwater runoff.
• Climate action: Cities can reduce their contribution to climate change by adopting renewable energy sources and implementing cleaner production techniques.
• Increased vulnerability: Urban expansion and the modification of landscapes make cities more vulnerable to natural hazards like floods and hurricanes.
• Amplified consequences: The high concentration of people in cities amplifies the potential for human and economic loss during natural disasters.
You can monitor air and sound using either smartphone apps or dedicated hardware sensors. For sound, use smartphone apps like Decibel X or NIOSH Sound Level Meter to measure noise levels, or for air, use dedicated air quality monitors like uHoo or Huma-i that measure pollutants like PM2.5, CO₂, and VOCs. You can also build a DIY system with sensors connected to a microcontroller like an Arduino or ESP8266 to create a custom monitoring setup that can send data to a smartphone app or web server.
Individuals and communities can take steps like reducing, reusing, and recycling waste, conserving water and energy, using sustainable transportation, and making conscious purchasing decisions. Community-level actions also include organizing cleanups, planting trees, supporting local and sustainable businesses, and advocating for environmentally friendly policies.
To improve your health and lifestyle, focus on a balanced diet rich in fruits and vegetables, regular physical activity for at least 150 minutes a week, and adequate sleep of 7-9 hours per night. Other key recommendations include managing stress, maintaining social connections, limiting alcohol, and avoiding smoking.