the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 30 Oct 2024
POPE: a Global Gridded Emission Inventory for PFAS 1950–2020
Abstract. This study presents a global multi compartment Persistent Organic Pollutant Emissions model and inventory: POPE. The model computes temporally and spatially resolved model ready emissions for 23 of the most widely used Per- and Polyfluoroalkyl Substances (PFAS) distinguishing between emissions to air and emissions to water covering the time span from the first industrial scale production in 1950 up until 2020 on an annual basis on a grid with 0.5° resolution.
The POPE model distributes estimated total PFAS emissions in space and time based on several data sets such as the E-PRTR, NACE and US-EPA FRS in combination with socio-economic data as population and GDP complemented by estimates for individual point sources, such as industrial sites and airports, whereby the source activity is dependent on regional changes in production volumes, usage quotas, and recapturing efficiency over time. It includes emissions by industrial production, diffuse emissions through usage and disposal of consumer products, secondary emissions from the reaction of precursors, and emissions by firefighting exercises on airports using Aqueous Film Forming Foams.
It is demonstrated that the POPE emission inventory is compatible with current global emission estimates, and temporal and spatial variability of the emissions is explored. A comparison of independent measurements with modelled river concentrations based on the POPE emission inventory is provided. The POPE emission inventory is meant to be used as input for atmospheric and marine chemistry transport models, eventually allowing to assess the environmental fate of PFAS. POPE can be used to create hypothetical future emission scenarios, enabling model based predictions which can inform policy decisions. This is important given that even with a theoretical global fade-out of PFAS production, significant legacy pollution is still to be expected.
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Status: final response (author comments only)
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RC1: 'Comment on essd-2024-236', Anonymous Referee #1, 27 Nov 2024
General Comments
This is a review of “POPE: a Global Gridded Emission Inventory for PFAS 1950-2020” by Simon et al., submitted to Earth System Science Data. This paper details the development of a global PFAS emissions inventory. The inventory includes 22 PFAS and covers the years 1950-2020, and can be updated with more species and years as data becomes available. This is a fantastic data set that will be of great use to the community, especially those trying to model PFAS in the environment.
Specific Comments
Line 2: how was “most widely used” determined?
Line 50: do you plan to include other POP’s in this inventory eventually? Otherwise shouldn’t it be named something specific to PFAS?
Line 57: technically no PFAS have been “outlawed” at least in the US (I’m not sure about elsewhere)—PFOA and PFOS were voluntarily phased out by companies
Line 77: just to clarify, all of the species except HFPO-DA and Adona are currently or soon to be regulated in the EU?
Table 1: suggest adding CAS numbers as well
Line 110: why just Swedish airports? Can you take the emissions from these 2 references and apply them to airports globally?
Table 2 is a bit hard to read as is—suggest left-justifying the text, or adding borders for the boxes maybe?
Line 164: do you have a reference for the statement that PFAS are typically polymerization aids? My understanding is that the monomers (e.g. TFE, HFPO, etc) are often emitted at large quantities as well. But I think the following statement is true regardless if the emission in question is a monomer or a processing aid?
Line 202: GenX is now produced by Chemours (which was formerly DuPont), I think DuPont did make it before they spun off Chemours in 2015 though
Line 204: this sentence is confusing as worded, both GenX and Adona can be used to make both PFOA and PFNA? I think either “both” should be replaced with “they”, or “respectively” needs to be removed
Line 213: this is a bit weird to give percentages without giving the base number for PFOS—can you give the base number here or tell the reader where that base number can be found in the manuscript or SI?
Line 277: what percent of airports is this? What defines “relevant” classes?
Line 278: what is the “huge disparity”? Much more emissions at which type of airport and ballpark/percentage how much more?
Line 279: why aren’t large civilian and military airports considered?
Line 302: should this be “the entire world”?
Section 2.4.2: Can you provide a map with the location of each of the sites?
Section 2.4: emissions are distributed equally between identified sources—can you comment on how realistic this is and how different allocations between individual sources might impact modeling results?
Line 386: PFAS were first produced sometime in the 1930’s-1940’s, suggest changing “the whole time span since the first production” to something like “the main time span of PFAS emissions, from early production in the 1950’s to present day”
Figure 1 (and all subsequent figures): maybe this is not the final figure, but could you please increase and bold font size, increase marker size, and increase line thicknesses?
Lien 407: do you need “seemingly” here? Since you show the exponential curve with it?
Line 454: why might POPE be underestimating the time lag?
Line 471: this sentence is confusing to me, I think maybe “Apart” is not the correct word to use? And the wording of “has to be captured by POPE”? Are you trying to say something like “Consumption of PFAS-containing products grows as the number of people and their income grows, which is captured by POPE”?
Line 571: see previous comment, I’m not sure you can definitively say 1950 was the first year PFAS were emitted to the environment. Could alter this sentence to say something like: “are, for the most part, temporally complete.”
Line 578: do you have a reference for this being the largest PFAS emitter? I’m not sure that is the case?
Line 629: the sentence starting “Also the general trend…” is confusing to me, could you please re-word it for clarity?
Figure 9: suggest spelling out “Modeled” on the x-axis, and if possible reversing the legend (not necessary, may be too difficult, but would be nice)
Line 795: see previous comments, suggest changing “beings with the first production of PFAS in 1950” to something like “begins with the year 1950”
Grammatical
Line 57: replacement should be plural
Line 104: add a space between the end of the statement and the reference
Line 116: this is the first usage of WWTP as an acronym, please define (currently defined on line 147, are there supposed to be hyphens between the words?)
Lines 133, 151, 152, 165, & 619: fluropolymer is missing an o
Lines 149 & 304: should be “Fluoropolymer production”—fluoro is missing an o, and add a space between the two words
Line 210: looks like these references are repeated
Line 250: should “on airports” be “at airports”?
Line 440: Other misspelled as Other
Line 556: should “again” be here?
Line 564: precoursor should be precursor
Line 567: should not be a period between alone and despite
Line 628: “mostly in form” should be “mostly in the form” I think
Line 655: should be “the results show a varied picture”
Line 753: “depicted in in Figure 6” – remove one of the “in”
Line 765: “of an total”—an should be a
Line 766: underestimations should be singular
Line 775: “is leads”—remove the “is”
Citation: https://doi.org/10.5194/essd-2024-236-RC1 -
RC2: 'Comment on essd-2024-236', Anonymous Referee #2, 17 Mar 2025
The authors built a global emission inventory for 23 PFAS at an annual 0.5-degree resolution over 1950-2020. Collecting data comprehensively for this inventory is a lot of work. The methodology is clear and well-referenced. My comments are as follows.
The only major concern I have is the evaluation of uncertainties from various data sources. The authors should discuss more about how the uncertainties are considered in the method, and how the uncertainties from the original datasets influence the key conclusions from the results.
Specific comments:
Title: I recommend adding spatial and temporal resolution in the title.
Abstract: The journal requires a link to the data repository in the abstract, which is currently missing. Since I don’t have access to the data, I cannot evaluate the data quality beyond what is presented in the manuscript.
L89: Please add more information on the downscaling process.
L110: why Swedish airports? How representative are they?
L119: please be more specific about what these datasets are.
L372: ‘caused by’ – ‘from’
L531-532 ‘As … estimates’: this sentence is not clear to me, please rephrase.
Figure 6: if ‘Asia’ represents ‘Asia excluding Japan’, please be clear about it.
L581: is it concluded from Figure 5 or elsewhere? I couldn’t find it.
L681-683 ‘A fraction …the USA’: why is it? Could you explain more?
Figure 8: please increase the limit of y-axis. Currently the whisker-bars of Haw-River and Ohio-River are out of the plot.
Citation: https://doi.org/10.5194/essd-2024-236-RC2
Data sets
POPE model and Data v2.0 Pascal Simon https://zenodo.org/records/12783504
Model code and software
POPE emission model Pascal Simon https://doi.org/10.5281/zenodo.12172268
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