**Revised 2/5/2009 1**  UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NC 27711
OFFICE OF AIR QUALITY PLANNING AND STANDARDS



### DRAFT Technical Note – Lead (Pb) Ambient Air Monitoring N etwork Design Issues

BACKGROUND

**On November 12, 2008 EPA substantially strengthened the national ambient air quality standards**  **(NAAQS) for lead (see 73 FR 66964). EPA revised th e level of the primary (health-based) standard**  **from 1.5 micrograms per cubic meter (μg/m 3**  **) to 0.15 μg/m 3**  **, measured as total suspended particles (TSP) and revised the secondary (welfare-based) standard**  **to be identical in all respects to the primary stan dard.**  **In conjunction with strengthening the lead (Pb) NAA QS, the EPA promulgated new monitoring**  **requirements including new design requirements for the Pb NAAQS surveillance network (40 CFR Part**  **58, Appendix D, paragraph 4.5). Monitoring is now required for Pb sources that may contribute to**  **violations of the Pb NAAQS [“source-oriented monito ring”, paragraph 4.5(a)]. Monitoring is also**  **required in large urban areas [“non-source-oriented monitoring”, paragraph 4.5(b)].** 

SOURCE-ORIENTED MONITORING REQUIREMENTS

What Pb sources need to have a source-oriented Pb m onitor?

**According to 40 CFR Part 58, Appendix D, paragraph 4.5(a), state and, where appropriate, local agencie**  **s are required to conduct ambient air Pb monitoring c**  **onsidering Pb sources that are expected to or have**

**been shown to contribute to a maximum Pb concentrat ion in ambient air in excess of the NAAQS. At a**  **minimum, there must be one source-oriented SLAMS si te located to measure the maximum Pb**  **concentration in ambient air resulting from each Pb source that emits 1.0 or more tons per year, unles**  **s the appropriate EPA Regional Administrator grants a**  **waiver.**

When are source-oriented Pb monitors required to be gin sampling?

**According to 40 CFR Part 58.10(a)(4), source-orient ed Pb monitors are required to begin sampling by**  **January 1, 2010. Monitoring agencies are required to identify which Pb sources will be monitored and**  **site locations in their annual network plan require d to be submitted to the EPA Regional Administrator**  **by July 1, 2009.**

What emission estimates should be used for determin ing if a Pb source emits at least 1.0 tons per year?

**According to 40 CFR Part 58, Appendix D, paragraph 4.5(a), monitoring agencies are to use either the**  **most recent National Emission Inventory (NEI, http: //www.epa.gov/ttn/chief/eiinformation.html) or othe**  **r scientifically justifiable methods and data (such a**  **s improved emissions factors or site-specific data) to**  **determine if a Pb source emits more than 1 ton per year. In addition to the NEI, monitoring agencies**  **should also consider Toxics Release Inventory (TRI, http://www.epa.gov/tri/) estimates. Examples of** **Revised 2/5/2009 2** 

**site-specific data include stack test data, permit limits, and other sources of information that may b**  **e more appropriate than estimates based on AP-42 emission**  **estimates. Emission estimates should be rounded to one decimal place using conventional rounding proce**  **dures.**

Under what conditions can a waiver for a source-ori ented monitor be granted?

**According to 40 CFR Part 58, Appendix D, paragraph 4.5(a), a monitoring agency can receive a waiver**  **from the source-oriented monitoring requirement for a given source emitting 1.0 or more tons per year**  **of**

**Pb if it can demonstrate that the Pb source will no t contribute to a maximum Pb concentration (based o**  **n a maximum 3-month rolling average over three years of**  **monitoring data) in ambient air in excess of 50% of the NAAQS (based on historical monitoring data,**  **modeling, or other means).**

Is a waiver needed for Pb sources with emissions of less than 1.0 tons per year?

**Waivers are only required for Pb sources with emiss ions greater than or equal to 1.0 tons per year.**  **Monitoring agencies are encouraged to review and im prove, if appropriate, National Emission Inventory**  **(NEI) emission estimates for all lead sources inclu ding those identified as having an emission rate of**  **1.0 tons per year. If a monitoring agency determines t**  **hat a source of Pb emissions is less than 1.0 tons per**  **year, they are to document the revised emission est imate in the monitoring plan required by 40 CFR par**  **t 58.10(a)(4), subject to public comment and the EPA**  **Regional Administrator’s review and acceptance,**

**and should submit the corrected emission estimate t o the NEI.** 

How should Pb monitoring locations be selected for source-oriented monitors?

**According to 40 CFR Part 58, Appendix D, paragraph 4.5(a), source-oriented monitors are to be sited at**  **the location of predicted maximum concentration in ambient air taking in to account the potential for**  **population exposure, and logistics. Typically, dis persion modeling will be required to identify the**  **location of predicted maximum concentration.**

**Locations may be selected that are not the maximum concentration when it is not practical to locate a**  **monitor (e.g., the location of maximum concentratio n is located in a road, or in a lake), or where the**  **re is no potential for population exposure (e.g., remote**  **mines with no nearby residences or community centers). In these cases, the monitor may be sited**  **at the location with the highest predicted concent ration**  **that is both practical and has the potential for po pulation exposure. Note that the potential for hum**  **an exposure is not necessary for a location to be cons**  **idered valid for the purpose of compliance with the Pb**  **NAAQS, however, monitoring agencies are allowed to consider the potential for human exposure when**  **selecting a monitoring location.**

**The location must also meet the siting requirements of 40 CFR Part 58, Appendix E.** 

What is the definition of “ambient air”?

**Ambient air is defined in 40 CFR Part 50.1 as “that portion of the atmosphere, external to buildings,**  **to which the general public has access.” The EPA has**  **developed a number of memorandums which help to interpret the definition of ambient air, including**  **the following –**

**http://www.epa.gov/scram001/guidance/mch/ama1.txt http://www.epa.gov/scram001/guidance/mch/ama2.txt** **Revised 2/5/2009 3** 

**http://www.epa.gov/scram001/guidance/mch/ama3.txt http://www.epa.gov/scram001/guidance/mch/ama4.txt**  **http://www.epa.gov/scram001/guidance/mch/ama5.txt**

**Monitoring agencies are encouraged to contact their EPA Regional monitoring contact if they have**  **additional questions regarding the definition of am bient air.** 

Where should source-oriented monitors be location f or airports?

**As with other Pb sources, source-oriented monitors for airports should be sited in ambient air at the**  **location of predicted maximum Pb concentration. Ty pically, the location of maximum Pb concentration**  **will be downwind of the take off strip near the “bl ast fence.”** 

Do existing source-oriented monitoring sites that a re not sited at the location of predicted

maximum concentration need to be moved to the locat ion of predicted maximum concentration?

**According to 40 CFR Part 58, Appendix D, paragraph 4.5(a), source-oriented monitors are to be sited at**  **the location of predicted maximum concentration in ambient air taking in to account the potential for**  **population exposure, and logistics. As such, exist ing sites that are not located at the location of** 

**maximum should be moved to the location of maximum concentration in ambient air taking in to account**  **the potential for population exposure, and logistic s. However, if the existing monitoring site is cur**  **rently measuring Pb concentrations that exceed the Pb NAAQ**  **S on a 3-month rolling average, a new site should be established at the location of predicted maximum**  **concentration, and the existing site should be maintained for a long enough period to demonstrate**  **that the new site is consistently measuring higher Pb** 

**concentrations.**

How many years of historic data are required to dem onstrate ambient concentrations are less than 50% of the NAAQS when requesting a source-oriented monitor waiver?

**The new monitoring requirements do not specify how many years of data are necessary to demonstrate** 

**that ambient concentrations are less than 50% of th e NAAQS when requesting a source-oriented monitor**  **waiver. As such, it is up to the EPA Regional Admi nistrator’s judgment how much data is necessary to** 

**demonstrate that ambient concentrations are less th an 50% of the NAAQS when requesting a source**  **oriented monitor waiver. Clearly, three complete y ears of monitoring data which demonstrates ambient**  **concentrations are less than 50% of the NAAQS shoul d be sufficient. However, there may be cases**  **where Pb concentrations are so low that just 1 year of data may be sufficient, in the EPA Regional**  **Administrator’s judgment, to determine that ambient concentrations are less than 50% of the NAAQS.** 

How recent must historical monitoring data be for u se in requesting a source-oriented monitor

waiver?

**The new monitoring requirements do not specify how recent historical data must be to demonstrate that** 

**ambient concentrations are less than 50% of the NAA QS when requesting a source-oriented monitor**  **waiver. As such, it is up to the EPA Regional Admi nistrator’s judgment to determine how recent** 

**historical data must be and still be usable to demo nstrate that ambient concentrations are less than 5**  **0% of the NAAQS when requesting a source-oriented monitor**  **waiver. Revised 2/5/2009**  **4**

**There are a number of practical considerations that apply to the use of historical data. For example,**  **data collected before 1990 are unlikely to be useful for**  **this purpose as most areas of the country had ambi ent**  **Pb concentrations greater than 50% of the NAAQS due to the use of Pb in gasoline. Also, changes to th**  **e emission characteristics of a site (e.g., a signifi**  **cant increase in emissions) occurring after monitor ing had**  **ended should be considered when determining if hist orical data is still appropriate for use in request**  **ing a**

**waiver.**

Must historical data used to support a source-orien ted monitoring waiver be obtained from FRM

or FEM Pb-TSP monitors?

**The new monitoring requirements do not state that h istorical data must be collected with an FRM or FEM**  **to be used in requesting a waiver. As such, other non-FRM or FEM monitoring data may be used if,**  **based on the EPA Regional Administrator’s judgment, the sampling and analysis methods provide a**  **scientifically sound estimate of Pb-TSP. For examp le, the EPA Regional Administrator may accept Pb** 

**PM 10**  **measurement collected using either a low volume or high volume PM**  **10 sampler in areas where Pb**  **is not expected to be in the ultra-coarse fraction of PM.** 

When may Pb-PM 10 monitors be used for a source-oriented monitor?

**According to 40 CFR Part 58, Appendix C, paragraph 2.10, Pb-PM**  **10 samplers can be approved for use at**  **source-oriented sites if the monitoring agency can demonstrate (through modeling or historic monitorin**  **g data from the last 3 years) that Pb concentrations**  **(either Pb-TSP or Pb-PM 10**  **) will not equal or exceed 0.10 micrograms per cubic meter on an arithmetic 3-**  **month mean and the source is expected to emit a substantial majority of its Pb in the fraction of P**  **M with an aerodynamic diameter of less than or equa l to** 

**10 micrometers.**

How would one determine if a source is expected to emit a substantial majority of its Pb in the fraction of PM with an aerodynamic diameter of less than or equal to 10 micrometers?

**AP-42 contains particle size distributions for a nu mber of common emission sources which can be used**  **in the absence of site specific particle size distr ibution information. Judgment should be used in th**  **e absence of applicable AP-42 guidance based on the n**  **ature of the emission source, any applicable controls, etc. For instance, Pb emissions from a m**  **elting pot (such as used in Pb casting operations) would primarily be emitted as a fume and would not**  **be expected to contain Pb in coarse particles. However, fugitive emissions from a storage pile of**  **crushed batteries (as found at a secondary lead smelter) would be expected to contain Pb in ultra-c**  **oarse PM.**

NON-SOURCE-ORIENTED MONITORS

In what urban areas are non-source-oriented monitor s required?

**According to 40 CFR Part 58, Appendix D, paragraph 4.5(a), State and, where appropriate, local agencie**  **s are required to conduct Pb monitoring in each CBSA**  **with a population equal to or greater than 500,000 people as determined by the latest available census**  **figures.**

**At this time, the latest census estimates are provi ded at the following link -**  **http://www.census.gov/popest/metro/CBSA-est2007-ann ual.html** **Revised 2/5/2009 5** 

When are non-source-oriented Pb monitors required t o begin sampling?

**According to 40 CFR Part 58.10(a)(4), non-source-or iented Pb monitors are required to begin sampling**  **by January 1, 2011. Monitoring agencies are requir ed to identify which CBSA will be monitored and sit**  **e locations in their annual network plan required to**  **be submitted to the EPA Regional Administrator by July 1, 2010.** 

Under what conditions can a waiver be granted for a non-source-oriented monitor?

**There are currently no waiver provisions for non-so urce-oriented monitors. In some cases, non-source**  **Pb monitoring data may be available from an existin g station in an urban area required to have this**  **monitoring (e.g., a National Air Toxics Trends Stat ions). As long as the Pb monitoring station(s) mee**  **t the network design criteria and utilize an approved**  **Pb FRM or FEM, existing stations may be used to meet this requirement. Such monitors would still n**  **eed to be documented in the annual monitoring network plans that are due no later than July 1, 20**  **10.**

When may Pb-PM 10 monitors be used for non-source-oriented monitors?

**According to 40 CFR Part 58, Appendix C, paragraph 2.10 of Appendix C to 40 CFR Part 58, Pb-PM**  **10 samplers can be approved for use at non-source-orie**  **nted sites if the monitoring agency can demonstrate there is no existing monitoring data indicating tha**  **t the maximum arithmetic 3-month mean Pb concentration (either Pb-TSP or Pb-PM**  **10 ) at the site was equal to or greater than 0.10 mic**  **rograms per cubic meter during the previous 3 years.** 

How should Pb monitoring locations be selected for non-source-oriented monitors?

**According to paragraph 4.5(b), non-source-oriented sites must be located to measure neighborhood scale**  **Pb concentrations in urban areas impacted by re-ent rained dust from roadways, closed industrial source**  **s which previously were significant sources of Pb, ha**  **zardous waste sites, construction and demolition projects, or other fugitive dust sources of Pb. Mo**  **deling is not needed to locate these monitors becau se**  **these monitors are intended to be neighborhood scal e monitors rather than “maximum concentration”** 

**monitors.**

**The location must also meet the siting requirements of 40 CFR Part 58, Appendix E.** 

Who should I contact to determine the locations of hazardous waste sites, construction and demolition projects, or other fugitive dust sources of Pb?

**Monitoring agencies should contact their state or R egional contacts for air permitting and or Superfun**  **d for assistance in identifying the locations of haza**  **rdous waste sites, construction and demolition proj ects,**  **or other fugitive dust sources of Pb. Revised 2/5/2009**  **6**

OTHER ISSUES

What should be done about existing Pb monitors that do not meet either of the source-oriented or non-source-oriented requirements? Should they be c ontinued?

**Monitoring agencies that will be required to operat e either a source-oriented or non-source-oriented**  **monitor are encouraged to relocate existing Pb moni toring sites to locations suitable to meet the new**  **monitoring requirements. However, monitoring sites that are currently identified as exceeding the Pb**  **NAAQS should not be moved or relocated if they are they are showing the highest Pb concentrations (on**  **a 3-month rolling average) at this time.**

**Monitoring agencies that will not be required opera te either a source-oriented or non-source-oriented**  **monitor may discontinue an existing Pb monitor acco rding to the requirements of 40 CFR Part 58.14.** 

FOR FURTHER INFORMATION

**This document and other documents intended to assis t monitoring agencies implement the Pb monitoring**  **requirements can be found at - http://www.epa.gov/ttn/amtic/pb-monitoring.html** 

**For additional information, please contact Kevin Ca vender of the Air Quality Assessment Division,**  **Ambient Air Monitoring Group, 919-541-2364, cavender.kevin@epa.gov** 

**.**