Abs: A newly proven technology exists that allows industrial operators, researchers, and regulators to monitor short-term variations in airborne metals concentrations in near-real-time (NRT) intervals. This tool, a mobile ambient air X-ray fluorescence metals monitor, has proven itself to be a reliable, precise, and accurate monitor that has been validated through comparisons with federal reference method (FRM) sampling and laboratory analysis.
Airborne metals and metal compounds are of particular concern to human health. Not only are they included in the United States (U.S.) Environmental Protection Agency’s (EPA) list of 187 hazardous air pollutants (HAPs), they represent 8 of the 33 urban pollutants identified by the EPA as posing the greatest potential health threat in urban areas. Contemporary researchers in the field of airborne metals’ health effects are finding that the metals components of PM are particularly toxic and cause a multitude of significant health effects from pulmonary inflammation, to increased heart rate variability, to decreased immune response. These effects are not only seen from chronic exposure, but also from short-term acute concentration spikes in ambient air.
A significant portion of the U.S. population lives in the vicinity of metals sources, such as waste incinerators, metal processors, metal fabricators, welding facilities, etc., where they may be exposed to airborne metals greatly in excess of typical ambient concentrations. With modern regulatory limits and controls on stack emissions at industrial facilities, many of the major regulatory and technological issues surrounding stack fumigation and pollution have been resolved.
Alternately, fugitive emissions, also described as uncontrolled process emissions, occur at or near local elevations and can dominate local hazardous air pollutant exposure. In fact, recent modeling at secondary lead smelters indicates that at many facilities the majority of daily emissions are fugitive in nature. Additionally, at facilities such as primary and secondary lead smelters, short-term lead concentration spikes may comprise the majority of the mass of lead emissions and subsequent human exposure for a given month. Fugitive emissions typically occur intermittently and unpredictably throughout the course of a plant’s daily operations. In addition, fugitive emission transport and exposure to human receptors may depend upon specific meteorological conditions, wind direction, and facility operations. Because these emissions are not measured by typical stack monitors, the specific source of the emission can be difficult to identify and control.
Presently, a newly proven technology exists that allows industrial operators, researchers, and regulators to monitor short-term variations in airborne metals concentrations in near-real-time (NRT) intervals. This tool, a mobile ambient air X-ray fluorescence metals monitor, has proven itself to be a reliable, precise, and accurate monitor that has been validated through comparisons with federal reference method (FRM) sampling and laboratory analysis. In addition, performance specifications and on-going quality assurance procedures have been developed and tested. This monitor provides a means to fulfill regulatory goals for implementing emission and ambient air maximum achievable technologies (MACT), as required by the Clean Air Act. The procedure, presented in this document, describes how this new monitoring tool might be used in permitting, monitoring, and compliance applications. It is based on well established PM monitoring protocols covered extensively by the EPA and in published scientific literature. This guide covers key aspects unique to ambient air metals measurements, along with hypothetical examples of its application to selected real-world sources, such as a secondary lead smelter, a primary lead smelter, a primary copper smelter, a ferrous metal recycler, and a hazardous waste incinerator.
The procedure for measuring ambient air metals concentrations consists of six key steps:
Step 1. Define the Driver: It is assumed that the need to develop a fence-line metals monitoring plan is driven by either a source requesting a new or renewed permit to operate, a potential health concern based on previous ambient measurements, a need to monitor emissions at a remediation site, or to provide support for a state implementation plan (SIP).
Step 2. Define ambient goal or limit: This step requires the guide user to define an ambient limit or goal; i.e. metal and PM size fraction, concentration, averaging time, number of allowed exceedances.
Step 3. Review and Characterize the local Airshed features: Before the user can develop a monitoring plan, the relevant features of the local airshed, such as meteorological features, topography, and location of emissions sources, must be explicitly defined.
Step 4. Define parameters to be monitored: Once the problem has been defined and the airshed characterized, it is now possible to begin the planning step by defining the specific parameters to be measured.
Step 5. Define number, characteristics and location of monitoring sites: With the above information defined and available, it is now possible to define the number, purpose, characteristics and location for each monitoring site.
Step 6. Outline data processing and reporting channels: Reporting will be based around the specific monitoring and regulatory requirements of the program. Data reporting format, frequency, and extent will need to be defined considering the various public and private stakeholders involved in the ambient metals monitoring plan.
These tools, i.e. NRT monitoring, performance specifications, quality assurance procedures, and procedure guide, provide the data and feedback to regulators, facility operators, the public, and other stakeholders necessary to develop and enforce established not-to-be-exceeded health limits, action levels, and goals for ambient air metals concentrations. The multi-metals FLM has the ability to characterize short-term exposure to hazardous metals during a time when a growing body of evidence points to the significance of ambient air metals in contributing to adverse human health effects. Accurate, NRT data not only helps to identify source contributions to key emissions events, it provides an early warning system to protect public health, improve controls, and reduce future emissions. The capability to relate short-term airborne metals variability to wind conditions and plant operating processes provides a tool of unprecedented power for source apportionment, regulation, improved air quality, and protection of human health and the environment.