Air Monitoring Q&A

The main purpose of the website is to provide the current Community Air-Quality Level (CAL) at each monitor location within the community air monitoring network. The CAL is an estimate of the particulate matter air quality at that location and is linked to health recommendations. The CAL reported for each monitor is updated every 5 minutes to reflect current conditions.

Each monitor has a detailed data webpage that provides more information about what air quality is usually like at that location. For example, for each location, you can see the average air quality for the past 24 hours, past 30 days, and past 90 days. Air quality data are provided as CALs and as particulate matter (PM) concentrations. The data on this website are automatically reported from the monitors and have not been verified or validated, so should be considered preliminary and used with discretion.

The monitors have undergone validity checks under both lab and field conditions, and our network has quality control checks in place. Additionally, the monitors used by our network perform well in comparison to government monitors and in laboratory studies. However, the data on this website have not been additionally verified or validated. Therefore, the data should be considered preliminary and used with discretion.

Data from IVAN Air Monitoring can be used in a variety of ways, including:

• Find out the current air quality at one of the many monitor locations
• Take action as needed to reduce air pollution exposure for yourself and your loved ones
• Examine how particulate matter (PM) air pollution varies within the county

Data from IVAN Air Monitoring cannot be used to determine if air quality standards are being met. Only data from government regulatory monitors can be used to determine if air quality standards are being met.

The air monitors used for IVAN Air Monitoring are different from those used by the government for air quality regulation and measure particulate matter (PM) pollution differently. While our monitors have been shown to perform very similarly to government monitors when located next to each other, they will not produce the exact same measurements. Government regulatory monitors are considered to be the most reliable, yet their very high cost and large size make their use in a community air monitoring network unfeasible.

Aside from differences between the monitors themselves, there are a number of other reasons that data from IVAN Air Monitoring may differ from the government regulatory network, such as:

• Air quality can vary within short distances, so data from the larger number of community monitors may measure and show these differences better than the relatively few government monitors.
• Government monitors may measure other air pollutants besides PM, such as ozone, which may influence the overall air quality levels reported for these monitors. The community monitors used in Imperial only measure PM.
• While we do our best to ensure that the community monitors are functioning, from time to time a community monitor may require maintenance or stop reporting data.
• IVAN Air Monitoring reports data as Community Air-Quality Levels (CALs), which are slightly different from the Air Quality Index (AQI) reported by government monitors.

We recommend that users of IVAN Air Monitoring also look at the regional air quality reported by the government network.

For data requests, please email the project team’s scientific staff describing what data you would like, how you plan to use it, and how this will benefit the residents of Imperial County.

Air quality data for Imperial County is also available at the following websites:

• http://www.co.imperial.ca.us/AirPollution/
• http://imperialvalleyair.org/
• http://www.arb.ca.gov/adam/
• https://www.airnow.gov/

Community Air-Quality Levels (CALs) are used to describe air quality in terms of how harmful the level of particulate matter (PM) pollution in the air is to human health. The CALs are calculated for each monitor based on current concentrations, with the number and category updated on this website every 5 minutes. There are 4 CAL categories, each with an associated color and health recommendation. The CALs uses the same 4-color scheme as school flag programs within Imperial County.

*Sensitive groups include children, teens, older adults, pregnant women, and people with heart, lung, or other chronic diseases

The Community Air-Quality Levels (CALs) on our website and the Air Quality Index (AQI) used by government agencies both provide information about the general air quality levels and their risk to populations.

However, there are some differences to be aware of. While our CALs are calculated using the same method as the AQI, the air monitoring data come from a different type of monitor that performs slightly differently.

Furthermore, CALs do not contain categories beyond the unhealthy/red category, since we recommend that everyone take precaution when air pollution reaches that level of risk. This also aligns with the categories used by school flag programs in Imperial County.

We recommend that users also pay attention to government-reported air quality when examining community air monitoring data from this website, though there are important reasons why these data may differ. When in doubt, we recommend taking precaution and action based on the highest of the air quality readings that you are comparing.

The monitors send air quality data over the internet to our servers. After quality control, the data are converted into air quality measurements, which are then displayed on this website. Learn about the monitors themselves, validation studies, calculation methods, and more under technical information.

That means that data from the monitor are not being reported to the website. This can happen for several reasons. The monitor may have gotten disconnected from the internet and needs to be reconnected. Or, the monitor may require routine maintenance or may need to be replaced. Comite Civico del Valle staff and project scientists get automatic notifications if a monitor stops reporting data or if the data look unusual. They then take steps to make sure monitors are working correctly and reporting data to the website.

We use a light-scattering particle counter manufactured by Dylos (Dylos 1700), which has been modified by Dylos to include four size bins (>0.5 µm, >1 µm, >2.5 µm and >10 µm). We further customized the monitor to enable wireless Internet connectivity and measurement of temperature and humidity. The monitor is enclosed in a protective shelter that does not inhibit measurements. The monitors are light weight (around 1 kg) and much less costly than federal reference monitors.

Dylos 1700 air quality monitor

In contrast to government regulatory monitors that measure particle mass, the Dylos is a light-scattering particle counter. The number of particles in the air is measured by the amount of light that is redirected by each particle when passing through the detection area of the particle counter. This information, along with the temperature and humidity, is transmitted to the study servers in real-time through a wireless connection and then converted into a CAL.

We have evaluated the performance of the Dylos monitor by installing it next to a Beta Attenuation Monitor (BAM) in Calexico, operated by the California Air Resources Board (CARB). This allows us to directly compare data from the Dylos with data collected for state regulatory and air quality planning purposes. We found good correlation (~0.9) between our monitor’s 24-hour PM2.5 particle counts and CARB’s 24-hour BAM PM2.5 particle mass concentrations.

We have found similar correlations comparing Dylos data against data from a co-located Tapered Element Oscillating Microbalance (TEOM) PM instrument operated by the Imperial Irrigation District (IID) in the northern part of Imperial County.

Finally, the South Coast Air Quality Management District has done an independent evaluation of the Dylos and found very good agreement (R2=0.8) between the Dylos and a Federal Equivalent Monitor.

Step 1: Convert from counts to mass: The particle counts from the Dylos are converted to particle mass using an algorithm developed from data obtained from the comparison of the Dylos to federal equivalent monitors when co-located. This conversion takes into account relative humidity.

Step 2: Calculate concentrations: The particle mass results (in µg/m3) are averaged using the U.S. EPA NowCast method. The NowCast method produces a value for PM10 and PM2.5, which is an average of the previous 12 hours. If the air quality that day is stable, then the hours are weighted more evenly (approaching a 12‐hour average). If the air quality that day is changing, then recent hours are weighted more heavily (approaching an average of the most recent 3‐hours).

Step 3: Convert to Community Air-Quality Level: The resulting NowCast value (in µg/m3) is then converted to the Community Air-Quality Level (CAL) using the U.S. EPA Air Quality Index calculation method. CALs are categorized into 4 categories: green/low risk (0-50), yellow/moderate risk (51-100), orange/unhealthy for sensitive groups (101-150), and red/unhealthy (above 150). The 30-day and 90-day summary statistics for CALs are calculated using 24-hour AQIs.

The Community Steering Committee (CSC) identified 11 priority communities in Imperial County in which to place monitors. Over 45 residents from those communities participated in a two-day process to identify potential monitoring sites, collect data on these locations, and select their top choices. Except for a few sites that declined participation or did not meet technical criteria, we were able to place a monitor in at least one priority site per community.

After analyzing the data from these initial 20 monitors, we identified locations where additional air quality data was needed in order to fill in gaps in the monitoring network. Working with the CSC, we identified sites within these areas and are installing more monitors to complete the network.

Monitors at Torres-Martinez Reservation, State Park Road near Parkside Drive (in North Shore) and Oaxaca and Calle Villahermosa (in Mexicali) were added to the network with separate funding from the California Department of Public Health.

To learn more about the technical/research aspects of this project, please contact the California Environmental Health Tracking Program.

At the federal level, the U.S. Environmental Protection Agency (EPA) is responsible for regulating air quality. Under the Clean Air Act, EPA limits how much of a pollutant, including particulate matter (PM), can be in the air. These limits or standards are called the National Ambient Air Quality Standards and are intended to protect public health and the environment. The Clean Air Act allows states to adopt more stringent air quality standards than the federal outdoor air standards. California has set PM standards that are more protective of public health than the national standards.

The California Air Resources Board (ARB) is responsible for regulating air quality in California and monitors the regulatory activities of California’s local air districts. To monitor PM and other air pollutants, ARB uses a network of more than 250 air monitors in California. ARB operates some air quality monitors directly, while others are operated by local authorities, private contractors, and the National Park Service. The data collected by these government monitors are used to determine which areas meet state and national air quality standards.

The Imperial County Air Pollution Control District is one of 35 local air districts in California. Local air districts have primary responsibility for controlling air pollution from stationary sources.

Contact the Imperial County Air Pollution Control District (APCD) at (442) 265-1800 as soon as you notice a problem. Their website lists what information to provide in order to support their investigations. It also describes what to expect when you submit a complaint.

After contacting the APCD, we recommend that you also submit a record of the problem here on IVAN Imperial, including a note that APCD has been contacted. This ensures that the Environmental Justice Task Force- a group of community and government representatives that meet monthly to review and take action on reports submitted through IVAN Imperial- is aware of the complaint and that the complaint is documented on the IVAN Imperial website.

The California Air Resources Board and the Environmental Protection Agency websites have extensive information about air pollution.

Setting up a community monitoring network requires resources, expertise, community participation, and a number of other considerations. Because of their existing infrastructure, IVAN communities are particularly well-suited to leverage the web platform, community engagement protocols, and best practices developed through our project. The team behind the IVAN Air Monitoring may be able to provide guidance or assistance to other communities who are interested in setting up their own community air monitoring network. Please contact Comite Civico del Valle for more information.