An overview of selected emerging outdoor airborne pollutants and air quality issues: The need to reduce uncertainty about environmental and human impacts

Figures & data

Table 1. List of emerging air pollutants selected using the methodology shown in Figure 1 (gas and metals) or from literature (particles). Legend: CA: carcinogenic in animals, CH: carcinogenic in humans, TH: toxic in humans, MH: mutagenic in humans, LCH: likely carcinogenic in humans; EG: exceeding one or more provincial guidelines at least at one or more observing sites (G16; Galarneau et al. 2016), AG: approaching guidelines at least at one or more observing sites (G16); MIR: maximum weighted incremental reactivity (see definition in Supplementary material S1). ECCC: Environment and climate change Canada; rank: based on a score risk for health (ANSES 2018). UFPs: ultrafine particles, eNPs: engineered nanoparticles, WHO: World Health Organization, CASRN: Chemical abstract service registry number.

Compound	CASRN	ANSES (2018)	US/EPA	G16 ECCC	Notes
Gas (VOC)
Acrolein	107-02-8		CA and TH	EG	Measurement uncertainties
Acrylonitrile	107-13-1	Emerging (rank: 4^th)	Likely CH	EG	WHO guideline proposed
1,3 Butadiene	106-99-0	Emerging (rank: 1^st)	CH,MH	AG	Precursor of ozone; WHO guideline proposed
Chloroform	67-66-3		LCH	EG	More information needed
Dichloromethane	75-09-2		CA	AG	WHO guideline proposed
Ethylene oxide	75-21-8		LCH	EG	Hazardous pollutant (EPA), Ozone precursor 5^th rank for MIR (Table 3b)
Formaldehyde	50-00-0		LCH	AG	1^st rank for MIR (Table 3b); WHO guideline proposed
Naphthalene	91-20-3	Emerging (rank: 11^th)	LCH	AG	Anthropic sources only
Tetrachloroethylene	127-18-4		LCH	EG	Known as perc; WHO guidelines proposed
Toluene	108-88-3		TH	AG	MIR (2^nd rank in Table 3b) WHO guideline proposed
Trichloroethylene	79-01-6	Emerging (rank: 7^th)	CH/MH	EG	WHO guideline proposed
Metals
Arsenic	7440-38-2	Regulated in Europe	CTH	AG	WHO guideline proposed
Cadmium	7440-43-9	Regulated in Europe	LCH	AG	WHO guideline proposed
Manganese	7439-96-5	Emerging (rank: 2^nd)			WHO guideline proposed
Nickel	7440-02-0	Regulated in Europe	LCH	EG	WHO guideline proposed
Vanadium	7440-62-2	Emerging (rank: 8^th)	TH		WHO guideline proposed
Particles
UFPs	-	Emerging	LCH		Multiple health effects
Black carbon	-	Emerging	CH		Impact on climate warming
eNPs	-	Emerging from the nanotechnology industry	Suspected to have health impacts		Unknown health effects. Need more information
Bioaerosols	-	Emerging in the context of climate change	Multiple health effects		Allergenic, synergy with air pollution, impact on climate.

Table 2. Results of the prioritization algorithm (from Figure 1): a proposed selection of the most critical emerging outdoor pollutant.

Cumulative score achieved	Number of compounds achieving this score	List of compounds selected according to the cumulative score	Prioritization level
8	0	-	N/A
7	0	-	N/A
6	2	Acrylonitrile, 1,3-Butadiene	1
5	4	Arsenic, Tetrachloroethene, Toluene, Trichloroethylene	2
4	4	Ethylene oxide, Formaldehyde, Manganese, Nickel	3
3	6	Acrolein, Chloroform, Dichloromethane, Naphthalene, Cadmium, Vanadium.	4
2	24	1,2,4-Trimethylbenzene,1,3,5-Trimethybenzene, Antimony, Carbon disulfide, Chrome, Copper, Cyclohexane, Dimethyl disulfide, Dimethyl sulfide, Ethylbenzene, Hydrogen sulfide, Iron oxide, MEK, methylcyclohexane, m-p-Xylene, n-Butane, n-Heptane, n-Hexane, n-Octane, n-Propylbenzene, o-Xylene, Platine, Propene, Styrene (candidate for future selection)	5
1	222	Not selected for critical prioritization	6
0	More than 4000	Not selected for critical prioritization	7

Table 3. A) Top 10 highest average concentration during summer at the site under the plume of Montreal (based on ESOM-96 campaign), B) Top 10 highest percentage weighted MIR (Maximum Incremental Reactivity) percentage at a site under the plume of Montreal.

Chemical species	Mean concentration (% of total VOC mass)	Rank
Acetone	17.8	1
Formaldehyde	14.5	2
Ethane	7.5	3
Toluene	6.8	4
Acetaldehyde	6.2	5
Isopentane	5.2	6
MEK	4.0	7
Propane	3.8	8
Ethylene	3.5	9
Acetylen	2.5	10
A
Chemical species	Weighted MIR	Rank
Formaldehyde	0.215	1
Toluene	0.11	2
Acetaldehyde	0.105	3
Propionaldehyde	0.055	4
Ethylene	0.05	5
m-p-xylene	0.045	6
Acetone	0.04	7
Crotonaldehyde	0.035	8
MEK	0.025	9
Isopentane	0.02	10
B

Figure 1. Algorithm used to select emerging pollutants. ATSDR: Agency for toxic substances and disease registry. WHO: World health organization. MDDELCC: Ministère du Développement Durable, de l’Environnement et de la Lutte contre les Changements Climatiques, Québec. ANSES: Agence Nationale de Sécurité Sanitaire, Alimentation, Environnement, Travail (France). LCH: likely carcinogenic to human, CH: carcinogenic to human. TH: toxic or reprotoxic, CA: carcinogenic in animal, BGCK: background value (see definition in S1), EG: exceeding provincial guidelines, AG: approaching guidelines (within an order of magnitude), S10: Simpson et al. (2010).

Figure 2. Worldwide production of ammonia (1998–2017). Raw data obtained from. Raw data obtained from https://www.usgs.gov/centers/nmic/mineral-commodity-summaries

Table 4. Selected provincial guidelines with a factor of variability across provinces.

Compounds	24hr guideline	1 year guideline	Variability
acrylonitrile	-	(0.12 Ontario)(12 Quebec)	100
butadiene	-	(2 Ontario)(0.3 Quebec)	6.67
ethylene oxide	-	(0.04 Ontario)(0.0005 Quebec)	80
toluene	(400 Alberta)(2000 Ontario)	-	5
trichloroethylene	-	(2.3 Ontario)(0.4 Quebec)	5.75
arsenic compounds	(0.3 Manitoba) (0.3 Ontario)	(0.01 Alberta)(0.003 Quebec)	1 (24 hr)/3.33 (yr)
cadmium	(2 Manitoba)(0.025 Ontario)	(0.05 Ontario)(0.036 Quebec)	80 (24 hr)/1.39 (yr)
manganese	-	(0.2 Alberta)(0.025 Quebec)	8

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