Air Pollution Measurement Methods and Exposure Assessment Study Notes

Air Pollution Measurement Methods and Exposure Assessment

Introduction

• Overview of the lecture on air pollution measurement methods and exposure assessment.

• Objectives of the lecture:

  • Describe the main measurement methods for air pollution.

  • Understand the strengths and limitations of these methods.

  • Differentiate exposure from mere concentration measurements.

  • Practice calculations related to air pollution exposure and concentration.

Module Outline

• The course module on Air Quality and Noise, currently in Lecture 7.

• Upcoming lecture by Dr. Shannon Lim on dispersion modelling and emissions.

Air Pollution Measurement Methods

• Presentation of real-time air quality indices and wind patterns from the IQ Air Earth site using satellite observations and fixed air quality monitoring stations.

• Importance of colour scales used to express air quality to the public.

• Example: Air quality levels in New Zealand are marked as safe (green).

Impact of COVID-19 on Air Quality

• Comparative analysis of air quality data over three years (2019-2021) that show:

  • A clear drop in pollution levels in 2020 attributed to COVID-19 lockdown and reduced vehicle emissions.

  • Rebound of pollution levels in 2021 once restrictions were lifted.

Importance for Civil Engineers

• Understanding air quality is crucial for civil engineers involved in:

  • Urban planning.

  • Transport systems.

  • Infrastructure projects.

• Example of Christchurch: Implementation of low-emission signs led to improved air quality due to effective traffic planning.

• Evidence: A clear drop in nitrogen dioxide (NO₂) concentrations post traffic changes on Riccarton Road.

Classification of Measurement Methods

Types of Measurement Methods

• Passive vs. Active Methods:

  • Passive methods require no power (e.g., rainwater collection) and allow pollutants to diffuse naturally.

  • Active methods involve powered devices (e.g., pumps) to draw air for analysis.

• Direct vs. Indirect Methods:

  • Direct: Measure the actual pollutant concentration (e.g., weighing collected samples).

  • Indirect: Estimate concentration based on signals from other measurements (e.g., light scattering to infer particulate matter levels).

Reference vs. Sensor-Based Methods

• Reference Methods:

  • Approved by the U.S. Environmental Protection Agency (EPA).

  • Highly accurate but expensive to install, operate, and maintain. Limited to specific locations.

• Sensor-Based Methods:

  • Less expensive and capable of higher spatial resolution with extensive deployment across cities.

  • Can be fixed or portable. Suitable for personal exposure assessments.

Fixed Air Quality Monitoring Stations

• Functionality of traditional fixed monitoring stations:

  • Continuous analysis for pollutants (sulfur dioxide, nitrogen oxides, PM) using EPA-approved methods.

  • High accuracy regulatory-quality data, but limited in number and location.

• Example: Auckland has 10 fixed stations measuring various pollutants, crucial for tracking spatial and temporal trends.

• Importance of these stations in policy interventions aimed at emission reduction.

Air Quality Guidelines and Standards

• Regulatory framework under the Resource Management Act (New Zealand).

  • Establishes monitoring requirements for areas exceeding national environmental standards.

• World Health Organization (WHO) Guidelines:

  • Revised in 2021, reducing safe pollutant levels based on health research.

  • Non-legally binding yet serves as benchmarks for air quality management.

• Compliance monitoring is facilitated through fixed air quality monitoring stations comparing pollutant concentrations against these standards.

New Measurement Techniques

Passive Sampling Techniques

• Passive samplers, like diffusion tubes:

  • Used to gauge gases (e.g., nitrogen dioxide, volatile organic compounds).

  • Collect samples through diffusion over a specified exposure time (e.g., two weeks).

Low-Cost Air Pollution Monitoring Technologies

• Use of low-cost sensors gaining popularity for air quality monitoring:

  • Track particulate matter and gases.

  • Require calibration and regular maintenance for accuracy.

• Highlights the community engagement aspect of using low-cost sensors and real-time monitoring systems.

Mobile Air Quality Monitoring

• Rise of portable air quality monitors (e.g., blood oxygen monitors, wearable sensors):

  • Used for citizen science and urban pollution mapping.

  • Cost-effective, providing real-time data but requires careful calibration.

Filter-Based Sampling

• Traditional method using filters for particulate matter:

  • Measure concentration by comparing filter weight before and after exposure.

  • Can analyze chemical composition through advanced techniques (e.g., gas chromatography).

Exposure Assessment

Distinction between Concentration and Exposure

• Concentration: Level of a pollutant in the air at a given location.

• Exposure: Amount of pollutant inhaled by a person, influenced by:

  • Location and duration spent there.

  • Activities performed (e.g., indoor air purifier vs. outdoor exposure).

Factors Affecting Exposure

• Sources of air pollution:

  • Indoor sources (cooking, cleaning) vs. outdoor sources (traffic emissions).

• Building design, ventilation, and urban planning can mediate exposure levels.

• Human factors (age, activity level) impact actual exposure dosage and health responses.

Study Examples on Exposure Assessment

• Illustrative diagrams showing how urban layout affects pollution exposure for pedestrians and cyclists.

• Differentiation of carbon monoxide uptake across age and weight shows how individual characteristics affect health impacts.

Conclusions

• Final thoughts on the importance of understanding both measurement methods and exposure assessment in urban planning.

• Encouragement to engage with ongoing air quality studies and monitoring systems for effective policy development.