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Determination of heavy metals in the ambient atmosphere: A review

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Overview

This open-access-style narrative review in Toxicology and Industrial Health surveys roughly 70 peer-reviewed studies on the determination of heavy metals in ambient air (TSPM, PM10, PM2.5) published since 2006. The authors catalogue analytical methods (ICP-OES, ICP-MS, AES, AAS, XRF, PIXE), QA/QC practices (SRM/CRM use, blanks, replicates, inter-lab comparison), source-apportionment findings (industrial emissions, vehicular emissions, coal combustion, smelting, brake wear, secondary aerosols, dust resuspension, fireworks events), and meteorological influences on heavy-metal concentrations in particulate matter. Geographic coverage skews toward developing-country sites in China, India, and other Asian countries where concentrations run higher than in Europe and North America. No primary data are reported; the review’s quantitative content is reattribution of the cited primary sources. Evidence tier C: useful as a methodological and source-apportionment leads document and as exposure-pathway context for atmospheric deposition into food crops, not citable as direct evidence for occurrence values. Authors disclosed no conflicts of interest and no funding.

Key numbers

Scope of the review

  • Approximately 70 quality research papers published since 2006 reviewed.
  • Information tabulated for total suspended particulate matter (TSPM), PM10, and PM2.5.
  • Supplementary Table 1 (online; not in the PDF body) lists parameters analysed by the reviewed papers.

Carcinogen classification of the heavy metals discussed (attributed to IARC)

  • Group 1 (carcinogenic to humans): hexavalent chromium (Cr), metallic nickel (Ni) and its compounds, arsenic (As) and its compounds, cadmium (Cd) and its compounds — all attributed by the review body to IARC 2012.
  • Group 2A (probably carcinogenic): inorganic lead (Pb) compounds (IARC 2006).
  • Group 2B (possibly carcinogenic): metallic Pb (IARC 1987), methyl mercury (IARC 1993).
  • Group 3 (not classifiable): metallic Cr and trivalent Cr (IARC 1990), metallic mercury (Hg) (IARC 1993), organic Pb compounds (no year attribution in body text).
  • Cho et al. (2011): atmospheric Pb concentrations declined approximately 92% between 1980 and 2008, attributed to the ban on tetraethyl lead in gasoline. Pb-bearing particles found in size ranges 2.5–10.0 µm.
  • Martin et al. (2015): over the past several decades, biomonitoring showed Pb decreased by more than 126% (sic — review-text figure; original Martin et al. paper reports a decrease) while Cd, Ni, and Cr increased approximately 10, 13, and 16 times respectively (2012 vs 1941).

Source-apportionment summary tabulated by the review (Section “Concentrations and sources of heavy metals”)

The review concludes the major atmospheric sources of named elements:

  • Soil and resuspended dust — Ca, Mg, aluminum (Al), Si, Fe, Mn.
  • Vehicular emissions — Cr, Pb, Cu, Zn, Cd, Fe.
  • Industrial processes — As, Mn, Hg, Cd, Zn.
  • Coal combustion — As, Hg, Cr, Co.
  • Brake wear — Cu, Fe, Zn, Cr, Mn, Ni.

Fireworks-event elevations cited by the review

  • Diwali festival, India (Barman et al. 2008, Lucknow): 1.9–3.72× higher heavy-metal concentrations (Cd, Cr, Ni, Zn, Cu) during Diwali night than day-time.
  • Lantern Festival, Taiwan (Tsai et al. 2012) and Beijing (Wang et al. 2007): ~10× and ~5× higher Pb concentrations during festival vs non-festival periods.
  • Girona fireworks, Spain (Moreno et al. 2010): Pb ~7×, Zn ~4×, Cu ~5×, As ~2× during a major fireworks event.
  • Diwali, Delhi (Sarkar et al. 2010): ~3× higher Mn during fireworks vs non-fireworks periods.

Specific site-level findings the review extracts from primary papers

  • Karachi, Pakistan (Mansha et al. 2012): industrial emissions (oil burning, smelting, iron and steel industry) contributed up to 53% of PM2.5.
  • Hyderabad, India (Gummeneni et al. 2011): vehicular emissions plus resuspended dust contributed >57% of heavy metals associated with PM2.5 and PM10.
  • Guangzhou, China (Lee et al. 2007): elevated Cd, Pb, V, and Zn at urban and suburban sites in 2005 vs 2003.
  • Guiyu, southeast China (Deng et al. 2006): 4–33× higher Cr, Cu, and Zn at an e-waste recycling site than other Asian countries.
  • Stockholm, Sweden (Furusjö et al. 2007) and Copenhagen (Wahlin et al. 2006): brake wear identified as the major source for Cu, Fe, Zn, Cr, Mn, Ni, Pb (and Zr, Mo, tin (Sn), Sb, Ba).
  • Foshan, China (Tan et al. 2014): ceramic-industrial-site As above WHO standard reference; aluminium-industrial-park site elevated Cd.

Quality-assurance survey (Section “Quality management of analytical data”; Table 1)

  • Most reviewed papers were aware of QA/QC requirements; few did not report QA/QC details.
  • NIST SRMs commonly analysed: SRM-1648 (urban dust), SRM-1648a, SRM-1649a, SRM-1573a (tomato leaves), SRM-281 (ryegrass), SRM-1944, SRM-2783, SRM-2710, SRM-2709, SRM-2704, SRM-97, SRM-2711, IAEA-Soil 7.
  • Recovery ranges reported across reviewed papers spanned roughly 70–110% for various metal-matrix combinations (Table 1 entries).
  • Wang et al. (2006) detection limit for Hg in particulate matter: 3 pg/m³.
  • Karar and Gupta (2007) recoveries: 95–111%.
  • Karanasiou et al. (2007) recoveries: 84–95% (avg 90%).
  • Karar et al. (2006) recoveries: 79–107%.
  • Stortini et al. (2009) precision (RSD) for repeated standard-solution measurements: 0.46–3.00%.

Bio-monitoring and special-source items

  • Plant materials used as bio-monitors named in the reviewed corpus include mosses and lichens (Szczepaniak and Biziuk 2003; Harmens et al. 2010; Kularatne and Freitas 2013), epiphytic lichens (Kularatne and Freitas 2013), other plant materials (Serbula et al. 2012), and herbarium specimens (Martin et al. 2015).
  • Hexavalent Cr speciation studies named: Khlystov and Ma 2006; Meng et al. 2011; Świetlik et al. 2011; Tirez et al. 2011. The review flags that acid digestion can interconvert Cr species, lowering hexavalent chromium (Cr-VI) recovery.
  • For volatile metals (As, Se), the review recommends microwave-oven extraction to prevent loss of metal vapours during hot-plate digestion.
  • For Cu determination, the review flags that motor brushes in high-volume samplers can overestimate Cu and recommends brushless motors.
  • Hg determination in ambient air is under-reported relative to Pb and Cd despite Hg’s toxicity (Suvarapu et al. 2013).

Methods (brief)

Narrative review. Literature retrieved from Science Direct, Google Scholar, and ISI Web of Knowledge. Inclusion window: papers published since 2006 on heavy-metal determination in ambient air (TSPM, PM10, PM2.5). Approximately 70 papers tabulated. No PRISMA flow, no inclusion/exclusion criteria operationalised, no quality-assessment instrument, no quantitative meta-synthesis. Table 1 in the body (extending across pages 81–87) tabulates per-paper QA/QC details: reference, particle-size fraction, sampler type, number of samples, flow rate, sampling duration, filter material, quality-control practice, and quality-assurance practice (SRM/CRM use, recovery ranges).

Analytical-method families catalogued across the reviewed corpus:

  • Inductively coupled plasma — optical emission spectrometry (ICP-OES), atomic emission spectrometry (AES), mass spectrometry (ICP-MS).
  • Atomic absorption spectrometry (AAS) — graphite furnace and flame variants.
  • X-ray fluorescence (XRF).
  • Proton-induced X-ray emission (PIXE).
  • Gold amalgamation (Pandey et al. 2011): identified as the best technique for gaseous elemental Hg in ambient air.
  • IC-ICP-MS (Meng et al. 2011): hexavalent-Cr-specific method development.

Sampler types tabulated in Table 1: high-volume sampler (HVS), medium-volume sampler (MVS), low-volume sampler (LVS), reference ambient air sampler (RAAS), automatic atmospheric mercury vapour analyser (AAMVA), dichotomous samplers, PUF samplers, dust-fall samplers, fine particulate dust samplers (FPDS), Andersen cascade impactor, cyclone/annular denuder, automatic samplers, PM10 inlet, fine-particulate dust sampler (FPDS), respirable dust sampler (RDS).

Filter materials catalogued: quartz fibre filter (QFF), glass fibre filter (GFF), Teflon, Teflon-coated GFF, PTFE micro-fibre, polypropylene, cellulose, cellulose esters, Zefluor.

Implications

Certification: Limited direct value for HMTc threshold setting because the review reports no product-level occurrence data. The principal certification-side relevance is atmospheric-deposition contextualisation — the review documents that vehicular Pb, industrial Cd, coal-combustion As and Hg, and brake-wear Cu/Zn enter ambient air in concentrations that vary by site and meteorology, which is the upstream half of the soil-and-foliar deposition pathway implicated on several food-crop contamination pages. The QA/QC table is a useful primer for atmospheric-side method literacy when adjudicating crop or biomonitor sources that cite atmospheric deposition.

Courses: Suitable as an introductory module on atmospheric sources of heavy metals and on the analytical-chemistry landscape (ICP-OES vs ICP-MS vs AAS vs XRF; SRM/CRM use; speciation challenges for Cr and Hg). The fireworks-elevation observations (Diwali, Lantern Festival) are vivid teaching cases on episodic-source contributions. The review’s misattribution of certain figures (the “>126% decrease” wording for Pb) is a useful negative example for source-fidelity discussions.

App: Not a source of concentration values for ingredient or product pages. No occurrence ranges applicable to the contamination_profile schema.

Microbiome: No direct relevance.

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