Inhalation toxicity profiles of particulate matter: a comparison between brake wear with other sources of emission

Figures & data

Table 1. Sources used to collect PM2.5 and PM2.5 suspension sample code.

PM source	PM2.5 suspension sample code
ECE low-metallic brake pads including copper	BW-1 or brake wear 1
Semi-metallic brake pads without copper	BW-2 or brake wear 2
Non-asbestos organic (NAO) brake pads	BW-3 or brake wear 3
ECE-NAO hybrid brake pads	BW-4 or brake wear 4
Studded winter tires and asphalt concrete pavement	Tire/road wear
Modern wood stove with efficient combustion conditions	Modern stove
Old-fashioned wood stove with efficient combustion conditions	Old-fashioned stove
Diesel engine exhaust from EURO-III engine	Diesel engine exhaust
Poultry farm	Poultry farm

Table 2. Exposure metrics: mass, size and number concentrations.

PM source	Expo low				Expo medium				Expo high				SMPS		OPS
	Mass		PNC		Mass		PNC		Mass		PNC		Median		Median
	mg/m^3	SD	#/cm^3	SD	mg/m^3	SD	#/cm^3	SD	mg/m^3	SD	#/cm^3	SD	nm	GSD	nm	GSD
BW-1	9.1	4	122 000	24 000	8.7	4	112 000	22 000	8.6	3	101 000	21 000	67	2.09	440	1.42
BW-2	8.2	3	131 000	18 000	8.2	3	125 400	18 000	7.9	3	113 600	22 000	70	2.21	400	1.53
BW-3	3.3	1	156 000	14 000	3.4	1	150 000	14 000	3.9	2	141 000	30 000	58	2.06	430	1.43
BW-4	7.5	3	138 000	26 000	7.6	3	135 000	23 000	7.6	3	125 000	23 000	73	2.13	410	1.42
Tire/road wear	6.7	3	97 000	7000	6.9	3	98 000	14 000	6.8	3	90 000	19 000	58	2.06	530	1.95
Modern stove	8.3	3			8.6	3	66 000	38 000	8.5	3	84 000	40 000	93	2.19	510	1.49
Old-fashioned stove	9.7	4	115 000	24 000	9.8	4	118 000	22 000	9.4	4	110 000	21 000	113	2.31	450	1.45
Diesel engine exhaust	9.2	4	113 000	13 000	9.2	4	116 000	23 000	9.2	4	117 000	20 000	123	2.31	410	1.38
Poultry farm	8.8	4	119 000	14 000	9	4	119 000	12 000	8.6	3	110 000	18 000	91	2.17	920	2.07

The high exposure dose was not present for brake wear 3 PM but instead a very low exposure dose was included resulting in respectively a mass and PN (particle number) concentration of 3.3 ± 1 mg/m³ and 156,000 ± 14,000 #/cm³. Size is expressed as count median diameter.

Figure 1. Inflammatory parameters in bronchoalveolar lavage fluid 24 h post-exposure to re-aerosolized PM2.5 of different sources at very low (VL) (only for brake wear 3 PM), low (L), medium (M) or high dose (H) (not present for brake wear 3 PM) compared to controls. Data are expressed as mean ± SD (n = 4–5 per group).

Figure 2. Ranking of PM dose range (BMDL and BMDU) for inflammatory responses in the lung resulting in 20% extra fraction (PMN) or 20% change in response (total cells, MIP-2, KC) compared to controls. Dashed line BMDU infinitive; a dose–response is present, however, at the current doses the in- or decrease in dose–response is too small (<BMR) to derive a BMDU.

Figure 3. Ranking of PM dose range (BMDL and BMDU) for hematological parameters lung resulting in 10% change in response compared to controls. Dashed line BMDL to zero, the maximum response is already reached at the first dose, i.e. the BMDL lies somewhere between minus infinitive (i.e. zero) and the first dose. Dashed line BMDU infinitive, a dose–response is present, however, at the current doses the in- or decrease in dose–response is too small (<BMR) to derive a BMDU. Dashed line BMD confidence interval ranging from zero to infinitive; data were too scattered to enable dose response analysis.