Ron Williams, EPA

Ron Williams is an Air Climate and Energy Project Leader with the EPA Office of Research and Development’s National Exposure Research Laboratory. This work involves leading a team of chemists, engineers, exposure scientists, and other researchers in the area of advanced environmental monitoring techniques.  He has held senior research positions in private, academic and governmental research organizations for more than 34 years.  He is a recognized expert in the area of human exposure monitoring and has been responsible for designing, executing and summarizing some of the US EPA's largest human observational panel studies. His current research focuses on developing and evaluating emerging sensor technology and determining its applicability for meeting a wide variety of air quality monitoring needs.

(Bio added Sept. 2014)


The Role of Sensor Technology in Air Quality Monitoring

Ron Williams- US EPA, Office of Research and Development, Research Triangle Park, NC

The Environmental Protection Agency (EPA) has identified six “criteria pollutants” as pollutants of concern because of their impacts on health and the environment[1]. The criteria pollutants are ozone[2] (O3), particulate matter[3] (PM), carbon monoxide[4] (CO), nitrogen dioxide[5] (NO2), sulfur dioxide[6] (SO2), and lead[7] (Pb). Under the Clean Air Act, the EPA has established primary and secondary National Ambient Air Quality Standards (NAAQS) for these six pollutants. Primary standards are designed to protect public health, particularly sensitive populations, while secondary standards are designed to protect the public welfare which includes the environment. If a geographical area does not meet one or more of the NAAQS, it is designated as a non-attainment area and must design a plan to meet the standard[8]. NAAQS concentration limits are shown in Table 2-2. The current monitoring network for criteria pollutants is comprised of monitors that meet Federal Reference Method (FRM) or Federal Equivalent Method (FEM) requirements.  Monitors are operated by state, local and tribal air pollution agencies across the United States to assess pollutant concentrations in relation to the NAAQS; a variety of instruments and techniques are needed to measure specific pollutants. Regulatory monitoring generally requires very sophisticated and well-established instrumentation to meet measurement accuracy requirements and an extensive set of procedures to ensure that data quality is sufficient. These requirements (e.g., calibration, maintenance, audits, data validation)[9] help ensure the collection of high-quality data. Refer to 40 CFR Parts 50, 53, 58, and the QA Handbook Volume II for activities/criteria for monitoring network data. The overall quality and credibility of measurements are determined by both the type of instrument and how it’s operated.

National Air Toxics Trends Stations (NATTS) are set up across the United States to monitor air toxics. These stations ensure that quality data is collected in a consistent manner.[10]  Under the Clean Air Act, EPA also regulates a list of 187 hazardous air pollutants (HAPs), commonly referred to as air toxics.” Starting in 2003, the EPA worked with state and local partners to develop the NATTS program to monitor several air toxics. The principal objective of the NATTS network is to provide long-term monitoring data across representative areas of the country for priority pollutants, including benzene, formaldehyde, 1,3-butadiene, hexavalent chromium and polycyclic aromatic hydrocarbons (PAHs) such as naphthalene, in order to establish overall trends. Additionally, some regulated industrial sources are required to submit air toxics emissions information to the EPA. The quality and completeness of emissions data varies significantly by region and source. NATTS-related information can be found at: