Method for assessing exposure to airborne contaminants

Abstract

The present invention relates to a method for assessing and quantifying the extent of personal exposure to airborne contaminants, including per- and polyfluoroalkyl substances (PFASs), commonly found on industrial and commercial sites, which contaminants may be of concern from a health and environmental perspective. The method includes passing air, from an environment that may comprise contaminated airborne dust, through a filter for a sufficient period of time to collect a representative amount of the contaminated dust on the filter, removing the contaminated dust from the filter, desorbing the contaminant from the dust to produce an extract comprising the contaminant collected from the filter, measuring the amount of contaminant present in the extract, and determining the concentration of contaminant, thereby quantifying a person's exposure to the contaminant from the environment.

Description

METHOD FOR ASSESSING EXPOSURE TO AIRBORNE CONTAMINANTSPRIORITY DOCUMENTS

[0001] The present application claims priority from Australian Provisional Patent Application No. 2023903143 titled “METHOD FOR ASSESSING EXPOSURE TO AIRBORNE CONTAMINANTS” and filed on 29 September 2023, the contents of which are hereby incorporated by reference in their entirety.TECHNICAL FIELD

[0002] The present disclosure relates to a method for assessing and quantifying the extent of personal exposure to airborne contaminants, including per- and polyfluoroalkyl substances (PFASs).BACKGROUND

[0003] Industrial and commercial sites can be contaminated with a number of different organic and inorganic substances, including per- and polyfluoroalkyl substances (PFASs), which are of concern from a health and environmental perspective. For example, PFASs are a well-documented phenomenon and have been found in settled dust at fire stations and training facilities (Hall, S. M. et al. (2020) Env Sci & Tech vol 54(22), pp 14558-14567), aerosols associated with wastewater treatment plants and in the environment (Yao, Y. et al. (2016) Environmental Pollution vol. 212, pp 449-456), as well as in house dust (de la Torre, A. et al. (2019) Science of the Total Environment vol. 685, pp 308-314.

[0004] Contaminants may become airborne via several pathways including the volatilisation of neutral compounds, aerosolization of ionised compounds in water droplets, the disturbance and transport of contaminated construction materials and soils, crushing and cutting of contaminated concretes, disturbance of settled contaminant-containing dusts, emissions generated by the manufacturing industry, or via the disturbance of crystalised concentrated contaminants, particularly PFASs following the evaporation of Aqueous Film-forming Firefighting Foams (AFFFs) and other PF AS containing solutions. Food Safety Australia and New Zealand (FSANZ) recognises inhalation as a contaminant uptake pathway along with ingestion through contaminated food or water, and dermal contact (Food Standards Australia and New Zealand, 2017).

[0005] Currently, there exist standard methods for measuring exposure to airborne dust on work sites, such as Australian Standard AS 3640-2009: Workplace atmospheres - Method for sampling and gravimetric determination of inhalable dust. This is a standard method for sampling inhalable dust to assess occupational exposure and involves gravimetric sampling and analysis to quantify dust mass. While the method is well established for inhalable dust, it does not measure contaminants, such as PFASs directly, and cannot be used to measure occupational exposure to contaminants in dust in their originalform. In terms of PFASs, studies have been conducted measuring PFASs from atmospheric sources through settled dust and / or aerosolised PFASs (see, for example Barber, J. et al. (2007) J Env Monitoring vol. 9, pp 530-41, and Haug, L. et al. (2011) Env Sci & Tech vol. 45(19), pp 7991-7998). Other research has involved the swabbing or vacuuming of dust on surfaces. The swabs are then analysed and used to extrapolate the worker exposure to PFASs from the collected dust (see, for example, Gustafsson, A. et al. (2022) Chemosphere vol. 303(2), p 135061 and Tefera, Y. M. et al. (2022) Env Int vol. 168, pl70455).

[0006] However, to date, there has been no method developed that allows for the direct measurement of a worker’s exposure to contaminants, particularly PFASs, in airborne dust. There is thus a need to provide a simple quantitative method to enable the quantitation and assessment of the extent of exposure of workers to contaminants, including PFASs, via airborne mechanisms.SUMMARY

[0007] According to a first aspect, there is provided a method of quantifying personal exposure to a contaminant in airborne dust, the method comprising the following steps: a) Providing samples obtained by passing air, from an environment that may comprise contaminated airborne dust, through a filter for a sufficient period of time to collect a representative amount of the contaminated dust on the filter; b) Subjecting the filter to conditions suitable for removing the contaminated dust from the filter; c) Subjecting the contaminated dust obtained in Step b) to conditions suitable for desorbing the contaminant from the dust to produce an extract comprising the contaminant collected from the filter; d) Measuring the amount of contaminant present in the extract produced in Step c); e) Determining the concentration of contaminant by comparing the amount of contaminant measured in Step d) to a standard calibration curve prepared from solutions comprising the contaminant at a known concentration, thereby quantifying a person’s exposure to the contaminant from the environment.

[0008] The dust may be contaminated with a PFAS. The PFAS may be a PFAS that is carried by or attached to dust particles. The PFAS may not be in an aerosol or a gaseous form. The PFAS may be selected from perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS) and perfluorohexanesulfonic acid (PFHxS), and combinations thereof.

[0009] The filter may be composed of polyvinylchloride (PVC) or methyl cellulose (MEC). Preferably, the filter is composed of PVC.

[0010] The filter may be housed in a mobile active air sampler, such as a portable sampler worn by a person. The filter may be housed in a static active air sampler placed at a fixed location in the environment.

[0011] The conditions of Step b) may comprise washing the filter with a solution. The solution may be an aqueous solution. The aqueous solution may comprise an organic solvent that is soluble in water. The organic solvent may be acetone, an alcohol, or a mixture thereof. The alcohol may be isopropanol or methanol, or a mixture thereof. The solution may comprise water and the organic solvent in a ratio of 1 : 1.

[0012] Step c) may be carried out concurrently with Step b).BRIEF DESCRIPTION OF DRAWINGS

[0013] Embodiments of the present disclosure will be discussed with reference to the accompanying drawings wherein:

[0014] Figure 1 is a flowchart of one embodiment of the method of the present invention.DESCRIPTION OF EMBODIMENTS

[0015] The present inventors have devised a new method for quantifying and assessing the extent of a worker’s exposure to airborne contaminants. In one aspect, the present invention relates to a method of quantifying personal exposure to a contaminant in airborne dust, the method comprising the following steps: a) Providing samples obtained by passing air, from an environment that may comprise contaminated airborne dust, through a filter for a sufficient period of time to collect a representative amount of the contaminated dust on the filter; b) Subjecting the filter to conditions suitable for removing the contaminated dust from the filter; c) Subjecting the contaminated dust obtained in Step b) to conditions suitable for desorbing the contaminant from the dust to produce an extract comprising the contaminant collected from the filter; d) Measuring the amount of contaminant present in the extract produced in Step c);e) Determining the concentration of contaminant by comparing the amount of contaminant measured in Step d) to a standard calibration curve prepared from solutions comprising the contaminant at a known concentration, thereby quantifying a person’s exposure to the contaminant from the environment.

[0016] The method of the present invention can be used to quantify and assess the extent of a worker’s exposure to a contaminant and / or the transport of the contaminant via airborne mechanisms. The method can be used in any location where dust particles containing contaminants, such as PFASs, are generated through manufacturing, maintenance, remediation, and civil works. Therefore, the method is advantageous in that, due to its adaptability and portability, it can be applied to a variety of different scenarios and locations, including remote sites.

[0017] The method also makes the measurement and subsequent management of direct occupational exposure to contaminants, in particular PFASs, in inhalable dust through existing standardised sampling equipment possible, and can be used to quantitate airborne contaminant mass flows to the environment (from the source). The use of commonly implemented equipment also ensures that the data can be collected in a simple manner using readily available equipment, without complex training. Further, the method facilitates data collection and analysis in a timeframe that is practical and allows appropriate action to be taken in real-time upon receiving results (e.g., changing work methodology or suspending work to prevent generation of further dust).

[0018] The results of the method also provide an analytical measure that can be integrated with tolerable daily intake (TDI) in place of an exposure standard to provide context to the data with reference to human health risk.

[0019] The method of the present invention comprises, as a first step, providing samples obtained by passing air, from an environment that may comprise contaminated airborne dust, through a filter for a sufficient period of time to collect a representative amount of the contaminated dust on the filter. Typical environments include any location where dust particles to which contaminants are adsorbed or absorbed, such as PFASs, are generated through manufacturing, maintenance, remediation, and civil works. Examples of activities that may involve the generation of contaminated dust include: filling bags containing contaminated materials or emptying the bags into skips or other containers; weighing loose contaminated powders; cutting contaminated materials (e.g., example paving stones or concrete); sieving and screening operations involving contaminated materials; conveying contaminated materials by mechanical means or by hand; stockpiling large volumes of processed contaminated materials; crushing, grading, milling, grinding, sanding down or other similar operations involving contaminated materials; cleaning, maintenance and remediation work involving contaminated materials; handling livestock feed and bedding, and working with livestock and animal waste.

[0020] The dust created or released by these work processes or activities is made up of particles of materials, and the types of materials that make up the dust are therefore dependent on the nature of the work that is being performed at a site and the nature of the materials involved. The dust may therefore comprise particles of a number of different materials, including salts derived from dried foams and waters, sand, dirt, pollen, minerals, wood, micro-organisms, and vehicle and industrial exhausts, soils, mining tailings and by-products, industrial wastes, tunnelling and excavation spoils, rock, concrete and asphalt, or mixtures thereof.

[0021] The dust created or released by work processes or activities (such as those described above) is made up of particles that range in size from relatively large to very small. Smaller dust particles can stay airborne for a significant amount of time and can be classified into two groups:• Inhalable dust (smaller than 100 micrometres (pm)) - visible dust which can affect the upper respiratory system (the nose, mouth, throat or upper respiratory tract);• Respirable dust (smaller than 10 pm) - these dust particles are invisible under normal lighting conditions, and their extremely small size also means they may travel deep into lungs and lead to lung damage.

[0022] The filters used in the method of the present invention typically capture both types of dust. Contaminants present on the dust particles pose an additional health risk. The contaminants that may be present will reflect those that are typically present at the types of sites discussed herein, and include inorganic contaminants such as metals, metalloids, halogens and nutrients (particularly, one or more of antimony, arsenic, boron, cadmium, chromium, cobalt, copper, cyanide, fluoride, lead, manganese, mercury, molybdenum, nickel, phosphate, selenium, uranium, and zinc) and organic contaminants including, for example, polycyclic aromatic hydrocarbons (PAHs), total petroleum hydrocarbons (TPH), "benzene, toluene, ethylbenzene and xylenes" (BTEX), benzo [a] pyrene (B(a)P), volatile organic compounds (VOCs), organic pesticides and herbicides, fertilisers, polychlorinated biphenyls (PCBs), PFASs, dioxins, explosive residues, polybrominated diphenyl ethers (PBDEs), disinfection byproducts, and specific organic compounds such as naphthalene, carbon tetrachloride and trichloroethylene, N-(l,3- dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD), and combinations thereof. The contaminant may be an organic contaminant. The organic contaminant may be a PFAS. The PFAS is a PFAS that is carried by or attached to dust particles. The PFAS may not be in an aerosol or a gaseous form. The PFAS may be selected from perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS) and perfluorohexanesulfonic acid (PFHxS), and combinations thereof. The method of the present invention is particularly useful as it can be focussed on the contaminants that are typically present in airborne dust, and that also have existing toxicity data to which the results of the method of the present invention can be compared. The relevant PFASs in this regard are PFOA, PFOS and PFHxS. For example, the FSANZ Tolerable Daily Intake (TDI) for these three PFAS compounds is 20 ng / kg bodyweight / day for PFHxS plus PFOS, and 160 ng / kg body weight / day for PFOA. So, for a 78 kg adult human, the TDI for PFHxS plus PFOS is 1.56 pg, and for PFOA it is 12.48 pg.

[0023] The filter used in the method of the present invention may be composed of any material that is suitable to adhere dust particles thereto. The filters to be used in the method of the present invention are preferably compatible with the conditions of Step b) and / or Step c). For example, they are preferably not soluble in any solutions that are used in Step b) and / or Step c). Preferably, the filters also do not already comprise or contain any PFASs. The present inventors have found that polyvinylchloride (PVC) or methyl cellulose (MEC) filters are suitable filters, and that PVC filters are particularly suitable for use in the method.

[0024] The filter may be housed in a mobile active air sampler, such as a portable sampler worn by a person. The filter may be housed in a static active air sampler placed at a fixed location in the environment. The filter may be contained in a device, such as a sample head, which is a small unit that holds a collection filter in a reusable cassette, and is calibrated with a timing device. When attached to a suitable sample pump, inhalable and respirable particles collect on the filter and larger particles fall into a collection pot, at the base, to be discarded. Examples of sample heads include the Cyclone or the IOM sample heads manufactured by SKC. The sample heads are installed in active air samplers, which are attached to, or placed at, points of potential reception i.e., either on workers (e.g., attached to clothing) or in static positions within the receiving environment, in accordance with Australian Standard 3640. Examples of suitable active air samplers for use in the method include those manufactured by airmet, such as the PCXR8 Universal Air Sampling Pump and, for personal use, the AirCheck Essential+ Air Sampling Pump.

[0025] The present inventors have found that, to be representative of a worker’s temporal exposure and therefore to collect a representative amount of the contaminated dust on the filter, the air samplers may be placed within the worker’s breathing zone or a fixed position in the location to be tested, in accordance with Australian Standard 3640, with a measured volume of air flowing through at a constant rate (e.g., about 1 L / min, about 2 L / min, about 3 L / min, about 4 L / min or about 5 L / min), for a minimum of four hours.

[0026] In Step b) of the method of the present invention, the filter is subjected to conditions suitable for removing the contaminated dust from the filter. The conditions of Step b) may comprise washing the filter with a suitable solution, and collecting the eluate. Alternatively, other methods of removing the contaminated dust may be employed. The solution may be an aqueous solution. The aqueous solution may comprise an organic solvent that is soluble in water. The organic solvent may be acetone, an alcohol, or a mixture thereof. The alcohol may be isopropanol or methanol, or a mixture thereof. The solution may comprise water and the organic solvent in a ratio of 1 : 1.

[0027] In Step c) the contaminated dust obtained from the filter in Step b) is subjected to conditions suitable for desorbing the contaminant from the dust to produce an extract comprising the contaminant collected from the filter. Advantageously, the present inventors have found that using an aqueous alcohol solution in Step b) not only removes the contaminated dust from the filter, but also desorbs the contaminant from the dust particles. Therefore, Step b) and Step c) can be combined into one step if an appropriate washing solution is used. Accordingly, Step b) can be carried out concurrently with Step c). Then, optionally filtering the resultant solution with, for example, a glass fibre filter or a cellulose filter, produces an extract comprising the contaminant collected from the filter, with minimal dust or other unwanted species present in the extract.

[0028] In Step d), the amount of contaminant present in the extract produced in Step c) is measured. Any method for determining an amount of a compound present in a solution can be used. For example, the extract may be analysed using Liquid Chromatography Mass Spectrometry / Mass Spectrometry (LC- MS / MS). In LC-MS / MS, a sample solution containing the analyte of interest is pumped through a stationary phase (LC column) by a mobile phase flowing through at high pressure. Chemical interaction between the components of the sample, the stationary phase and the mobile phase affects different migration rates through the LC column affecting a separation. After elution from the LC column, the effluent is directed to the mass spectrometer. The mass spectrometer for an LC-MS / MS system has an ionization source where the LC column effluent is nebulized, desolvated and ionized creating charged particles. These charged particles then migrate under high vacuum through a series of mass analyzers (quadrupole) by applying electromagnetic fields. A specific mass / charge precursor ion (or parent ion) is targeted to pass through the first quadrupole, excluding all other mass / charge ratio particles. In the collision cell, the selected mass / charge ions are then fragmented into product ions (or daughter ions) by collision with an inert gas. The third quadrupole is used to target specific product ion fragments. The resulting isolated product ions are then quantified with an electron multiplier. The measurement of the amount of analyte (e.g., contaminant) in the extract may therefore involve calculating the area under an integrated peak, which peak is indicative of the quantity of the analyte (e.g., the contaminant). Any LC- MS spectrometer can be used for the measurement. An example of a suitable spectrometer is the Shimadzu LCMS-8060. It may also be possible to carry out the method of the present invention on-site, in which case a portable unit may be used.

[0029] To quantify a person’s exposure to the contaminant from the environment, the amount of contaminant measured in Step d) is correlated to a concentration of the contaminant using an appropriate calibration curve. Therefore, the method of the present invention also comprises the step of determining the concentration of contaminant by comparing the amount of contaminant measured in Step d) to a standard calibration curve prepared from solutions comprising the contaminant at a known concentration.

[0030] A person skilled in the art will be aware of how to prepare a suitable calibration curve. For example, the contaminant can be added to a stock solution in increasing known concentrations. Theconcentrations may be based on, for example, the TDI for the contaminant. For example, in the case ofPFASs, the concentration may range from 0.5 pg / L to 50 pg / L of the PFAS of interest. The stock solution may also comprise a dust. The dust may be a silica dust.

[0031] Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that such prior art forms part of the common general knowledge.

[0032] It will be understood that the terms “comprise” and “include” and any of their derivatives (e.g., comprises, comprising, includes, including) as used in this specification, and the claims that follow, is to be taken to be inclusive of features to which the term refers, and is not meant to exclude the presence of any additional features.

[0033] In some cases, a single embodiment may, for succinctness and / or to assist in understanding the scope of the disclosure, combine multiple features. It is to be understood that in such a case, these multiple features may be provided separately (in separate embodiments), or in any other suitable combination. Alternatively, where separate features are described in separate embodiments, these separate features may be combined into a single embodiment unless otherwise stated or implied. This also applies to the claims which can be recombined in any combination. That is a claim may be amended to include a feature defined in any other claim. Further a phrase referring to “at least one of’ a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c.

[0034] It will be appreciated by those skilled in the art that the disclosure is not restricted in its use to the particular application or applications described. Neither is the present disclosure restricted in its preferred embodiment with regard to the particular elements and / or features described or depicted herein. It will be appreciated that the disclosure is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope as set forth and defined by the claims.EXAMPLES

[0035] Example 1

[0036] The flow chart in Figure 1 summarises the following method.

[0037] Dust stock solutions

[0038] Individual dust stock solutions (780 pg / mL individual PFHxS, PFOA and PFOS) were prepared from solids of varying purity of PFHxS. K, PFOA and PFOS.K (>98%, >96% and >98%, respectively) dissolved in 50 mL of MeOH in 100 mL glass bottle with no PTFE liner. After addition of a PFAS salt and MeOH the bottle was capped tightly with parafilm around the outside cap and the solution was mixed using a mini vortex mixer for 30 seconds.

[0039] The PFHxS, PFOA and PFOS standards contain both branched and linear isomers which are then quantified using linear only standards and reported as the sum branched plus linear. The below formula was used to calculate the mass of PFHxS potassium (MW = 399.12 g / mol and MW = 39.0983 g / mol, respectively) and PFOS potassium (MW = 499.13 g / mol and MW = 39.0983 g / mol, respectively) required to make 50 mL of 780 pg / mL:ConcpFAs (mg / mL) = [Purity (%)] x { 1- [(MWcation ) / (MWPFASsait)] } x [MassPFAssait (pg)] x [vol (mL)] .

[0040] The purity of the PFOA standard (96%) is used to calculate the mass of PFOA required to make 50 mL of 780 pg / mL using the following formula:ConcpFAs (mg / mL) = [Purity (%)] x [MassPFoA (pg)] x [vol (mL)].

[0041] Individual dust stock solutions were prepared as shown in Table 1.

[0042] TABLE 1Individual dust stock solutions.

[0043] For dust sampling, the calibration solutions shown in Table 2 (using the same dust stock solutions) were prepared.

[0044] TABLE 2Individual dust stock solutions.

[0045] In the above table: Cal Check Intermediate solution refers to a solution that is diluted to 8 pg / L from a 2000 ng / mL reference standard containing 13 perfluoroalkylcarboxylic acids and 8 perfluoroalkylsulfonates (commercially available as PFACMXC0617 from Wellington Laboratories, Canada) used to verify the accuracy and reliability of the LC-MS / MS; surrogate stock solution is a solution containing mass labelled PFAS species, including MPFBA (13C4-Perfluoro-n-butanoic acid), M3PFPeA (13C3-Perfluoro-n-pentanoic acid), MPFHxA (13C2-Perfluoro-n-hexanoic acid), M4PFHpA (13C4-Perfluoro-n-heptanoic acid), MPFOA (13C4-Perfluoro-n-octanoic acid), MPFNA (13Cs-Perfluoro-n- nonanoic acid), MPFDA (13C2-Perfluorodecanoic acid), MPFUdA (13C2-Perfluoro-n-undecanoic acid), MPFDoA (13C2-Perfluoro-n-dodecanoic acid), M2PFTeDA (13C2-Perfluoro-n-tetradecanoic acid), M3PFBS (13C3-Sodium perfluoro-n- butanesulfonate), MPFHxS (18O2-Sodium perfluoro-n- hexanesulfonate), MPFOS (13C4-Perfhrorooctylsulf onate), M8PFOS (13Cs-Sodium perfluorooctanesulfonate) and M2PFOA (13C2-Perfluoro-n-octanoic acid) (see Table 3 below) prepared involving adilution with 95:5 MeOH / water - the surrogate stock solution is added at the start of the extraction procedure to the samples for tracking any losses of native PFAS compounds during the extraction procedure; UHP refers to ultra-high purity water obtained from Merck’s Milli Q Direct Water Purification System; MeOH acid adjusted is methanol acidified with acetic acid to a final concentration of acetic acid of 0.05%; the internal injection standards used are MPFDA (perfluoro-n-[l,2-13C2] decanoic acid), M2PFOA (perfluoro-n-[l,2-13C2] octanoic acid), and MPFOS (Sodium perfluoro- 1-[1, 2,3, 4-13C4] octanesulfonate) .

[0046] TABLE 3Surrogate stock solution (1000 mg / L).

[0047] Filter and dust sample preparation procedure

[0048] Dust samples were prepared as per ACM-P-01 Sampling and Gravimetric Determination of Respirable Dust (see Australian Standard AS2985-2009). Once received, filters were transferred to PP tubes and extracted as follows:(1) Spike with 233 pL of the Surrogate Stock Solution (see Table 3 above);(2) Add 10 mL of 1:1 MeOH / UHP solution and shake vigorously for 1 minute by hand;(3) After shaking, add 20 pL of ammonium hydroxide solution (25%) to adjust pH to 9-10, and the sample is then hand shaken again for 1 minute;(4) Tumble sample for 1 hour and then centrifuge at minimum 2800 rpm for 10 minutes (some samples may require a longer centrifuge at higher speeds to separate out any particles from the solution);(5) Wash a syringe and filter with two volumes of Milli Q water and using this syringe and filter to filter the supernatant into a PP tube (minimum 3 mL);(6) Take 1076 pL of supernatant into a sample vial, add 457 pL of 0.58 M acetic acid solution and add 20 pL Internal Standard Working Solution (see Tables 4 and 5 below);(7) Cap vial and shake vigorously.

[0049] TABLE 4Internal Standard Stock Solution (50 pg / L); dilution carried out with 95:5 MeOH / water.

[0050] TABLE 5Internal Standard Working Solution (3 pg / L); dilute Internal Standard Stock Solution (Table 5) with 95:5 MeOH / water.

[0051] QA / QC for dust samples were prepared as follows:Method blank: A clean filter is placed in a PP tube and extracted as per (1) to (7) above;Laboratory Control Sample: A clean filter is placed in a PP tube and spiked with 50 pL of theWorking Stock Solution and extracted as per (1) to (7) above;Matrix Spike: A client provided matrix sample is used, or if not available a clean filter with ~10 mg of silica dust added is placed into a PP tube and spiked with 50 pL of Working Stock Solution and extracted as per (1) to (7) above;Duplicate sample: A sample is selected, and an aliquot of extract is split and analysed in duplicate to confirm analytical results.

[0052] Calculating results

[0053] All peaks in a chromatogram were integrated and included in the calculation of results.

[0054] For the calculation of individual PFAS concentrations, surrogate response, and use of injection standards for compounds with labelled standards, the following was undertaken.

[0055] PFAS results are surrogate (SURR) corrected using a response factor (RF) derived from the mean peak area response of the relevant mass labelled surrogate (as referred to in Table 2 above) in calibration (CAL) standards:RF = [ (Area analyte CAL) / (Area SURR CAL) ] x [ (Cone SURR CAL) / (Cone analyte CAL) ]

[0056] PFAS concentrations are then surrogate corrected in the instrument software using the following calculation (where SAM is the PFAS -containing sample obtained from the field):PFASsc (ng / L) = [ (Area analyte SAM) / (Area SURR SAM) ] x [ (Cone SURR SAM) / (RF) ]

[0057] For water, surrogate corrected concentrations are reported. To calculate in soil, the following is used (where ES is the volume of solvent used for the extraction, W is the mass of sample used for extraction, FV is the final volume of solution used for the analysis, AT is the aliquot taken, and M is the moisture content):PFAS analyte (mg / kg) = PFASscx (ESAV) x (FV / AT) x 1 / (1-M)

[0058] To calculate PFAS per filter / dust using pg / mL calibration:PFAS analyte (pg / filter) = (PFASscx 1000 mL / lOmL) / 1000.

[0059] In some instances, trace amounts of contaminants may be detected during the analytical process. The present inventors have found, and a person skilled in the art will be aware, that this can be dealt with by conducting a thorough investigation to determine the source of the contamination. In the present inventors’ investigations for example, one such instance of contamination was identified asoriginating from the equipment used to calibrate the air samplers. The calibration method was updated to ensure air and dust passing through collection filters is not first passed through the equipment used for calibration. Another method of dealing with contamination, particularly where the source of the contaminant cannot be identified and / or the procedure cannot be modified to remove the influence of the contaminant, is to raise the Limit of Reporting (LOR). For example, in some studies performed by the inventors, PFOA was identified as such a contaminant, and the LOR was thus raised by a factor of 10% to 1.0% of TDI for all PFAS species (or just the PFOA LOR can be raised, such that, for example, PFOS is 0.1%, PFHxS is 0.1% and PFOA is 1.0%). The calibration method may also be modified to include both of these mitigation measures.

[0060] Background PFAS study

[0061] This case study outlines a broad assessment that aimed to determine background PFAS concentrations in dust across various undisturbed settings in contaminated and uncontaminated environments. Dust was sampled from sources such as manufacturing, maintenance, remediation, and civil works within PFAS -impacted sites or industries. At least three samples were taken from each location for 5 to 8 hours (corrected to an 8-hour work day) set out in Table 6 below, as follows:• Residential (Dwelling) - three samples (in duplicate) collected using three static samplers placed on a table in various locations within a home;• Residential (Gardens) - three samples (in duplicate) collected using three static samplers placed at head height in various locations in a backyard away from the property boundary;• Urban - two samples collected using two samplers mounted on the outside of a vehicle;• Office - three samples (in duplicate) collected using three samplers mounted outside offices at head height;• Airport (Personal Monitor) - three samples (in duplicate) collected using three samplers mounted on staff (in their breathing zone) onsite;• Airport (Static Monitor) - four samples collected using four static samplers placed in cardinal directions around concrete fire training pad coring (i.e. drilling works);• Laboratory - two samples collected using two static samplers mounted on equipment in soil processing and crushing room;Wastewater Treatment Plant spray field - five samples collected using static samplers on star pickets, spread across the study area.

[0062] The results of the study are given in Table 6 below. The Food Standards Australia New Zealand (FSANZ) Tolerable Daily Intakes (TDIs) for a 78 kg human are given in Table 7 further below.

[0063] TABLE 6Outcomes of field monitoring (% TDI)Notes:* During rain event, no ground disturbance** Concrete crushing room

[0064] TABLE 7FSANZ TDI and allowable exposure for average 78 kg human

[0065] The studies have revealed that airborne PFAS exposure can exceed the FSANZ TDI for PFOS+PFHxS (0.02 pg / kgbw / day) highlighting an exposure pathway that has generally not received sufficient attention in the assessment of PFAS risk. This is also true when evaluating certain modes of offsite or transboundary transport. The results suggest that under certain exposure scenarios, PFAS exposure neared the adopted threshold value (20% TDI for air in Australia), noting that no scenario above risk level LxE was tested. Importantly, scenarios with low or no PFAS concentration and low dust generation were demonstrated to produce a “non-detect” result.

[0066] Field trials

[0067] A series of field trials were conducted to monitor background PFAS in dust concentrations in and around Melbourne (Victoria, Australia) and Brisbane (Queensland, Australia) to test the apparatus suitability in environmental background sampling. This involved the placement of samplers as discussed in the list below (all containing a PVC filter) at static locations in and around Melbourne and Brisbane, and the sampling was conducted (in duplicate) for 8 hours over 1 day:• Rural / suburban - collected using samplers placed in the front yard of a home in a peri-urban area of Melbourne or Brisbane;• Industrial - collected using samplers mounted to fixtures (stairs or awning poles) at the front of buildings in industrial districts in Port Melbourne (Victoria, Australia) and Fortitude Valley (Queensland, Australia);• CBD - collected using samplers mounted on a parked vehicle in the city of Melbourne or Brisbane.

[0068] Following the completion of the exposure periods the filters were removed before being sent to the laboratory for extraction and analysis, as described above. The results are shown in Tables 8 and 9 (where A and B are the duplicates).

[0069] TABLE 8Results of Melbourne air sampling field trial in total pg / filter.

[0070] TABLE 9Results of Brisbane air sampling field trial in total pg / filter.

Claims

CLAIMS1. A method of quantifying personal exposure to a contaminant in airborne dust, the method comprising the following steps: a) Providing samples obtained by passing air, from an environment that may comprise contaminated airborne dust, through a filter for a sufficient period of time to collect a representative amount of the contaminated dust on the filter; b) Subjecting the filter to conditions suitable for removing the contaminated dust from the filter; c) Subjecting the contaminated dust obtained in Step b) to conditions suitable for desorbing the contaminant from the dust to produce an extract comprising the contaminant collected from the filter; d) Measuring the amount of contaminant present in the extract produced in Step c); e) Determining the concentration of contaminant by comparing the amount of contaminant measured in Step d) to a standard calibration curve prepared from solutions comprising the contaminant at a known concentration, thereby quantifying a person’s exposure to the contaminant from the environment.

2. The method of claim 1, wherein the dust is contaminated with a per- and / or polyfluoroalkyl substance (PFAS).

3. The method of claim 2, wherein the PFAS is a PFAS that is carried by or attached to dust particles.

4. The method of claim 2 or claim 3, wherein the PFAS is not in an aerosol or a gaseous form.

5. The method of any one of claims 2 to 4, wherein the PFAS is selected from perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS) and perfluorohexanesulfonic acid (PFHxS), and combinations thereof.

6. The method of any one of the preceding claims, wherein the filter is composed of polyvinylchloride (PVC) or methyl cellulose (MEC).

7. The method of claim 6, wherein the filter is composed of PVC.

8. The method of any one of the preceding claims, wherein the filter is housed in a mobile active air sampler, such as a portable sampler worn by a person.

9. The method of any one of claims 1 to 7, wherein the filter is housed in a static active air sampler placed at a fixed location in the environment.

10. The method of any one of the preceding claims, wherein the conditions of Step b) comprise washing the filter with a solution.

11. The method of claim 10, wherein the solution is an aqueous solution.

12. The method of claim 11, wherein the aqueous solution comprises an organic solvent that is soluble in water.

13. The method of claim 12, wherein the organic solvent is acetone, an alcohol, or a mixture thereof.

14. The method of claim 13, wherein the alcohol is isopropanol or methanol, or a mixture thereof.

15. The method of any one of claims 12 to 14, wherein the solution comprises water and the organic solvent in a ratio of 1 : 1.

16. The method of any one of the preceding claims, wherein Step c) is carried out concurrently with Step b).

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