Health effects of ultrafine particles: a systematic literature review update of epidemiological evidence

Abstract

Objectives Due to their small size, ultrafine particles (UFP) are believed to exert higher toxicity than larger particles. As numerous studies on health effects of UFP have been published since the last systematic review in 2013, we aim to systematically review the new literature. Methods We searched MEDLINE and the specialized LUDOK database for studies published between 01.01.2011 and 11.05.2017 investigating health effects of ambient air pollution-related UFP. We included epidemiologic studies containing UFP measures and quantifiable measures of associations. Relevant data were extracted on the basis of previously developed evaluation criteria. Results We identified 85 original studies, conducting short-term (n = 75) and long-term (n = 10) investigations. Panel (n = 32), scripted exposure with predefined settings (n = 16) or time series studies (n = 11) were most frequent. Thirtyfour studies adjusted for at least one other pollutant. Most consistent associations were identified for short-term effects on pulmonary/systemic inflammation, heart rate variability and blood pressure. Conclusions The evidence suggests adverse short-term associations with inflammatory and cardiovascular changes, which may be at least partly independent of other pollutants. For the other studied health outcomes, the evidence on independent health effects of UFP remains inconclusive or insufficient.

Hourly Exposure to Ultrafine Particle Metrics and the Onset of Myocardial Infarction in Augsburg, Germany

“…Toxicological studies have provided early evidence that UFP might have higher toxicity per mass unit than larger particles (HEI Review Panel on Ultrafine Particles 2013). However, epidemiological evidence on the association between UFP exposure and cardiovascular effects remains inconclusive and insufficient to infer a causal relationship despite an increasing number of studies over the past decade (HEI Review Panel on Ultrafine Particles 2013; Ohlwein et al 2019;Rückerl et al 2011).…”

“…The paucity of consistent findings across epidemiological studies may be in part due to the different size ranges and exposure metrics examined to characterize ambient UFP exposure (Baldauf et al 2016; HEI Review Panel on Ultrafine Particles 2013; Ohlwein et al 2019). Conventionally, UFP are defined as particles ≤100 nm in diameter, which consist of both primary particles (30-100 nm) emitted directly from vehicle exhaust (Aitken mode) and newly formed secondary particles (<30 nm) from mostly nucleation processes (nucleation mode) (Brines et al 2015;Morawska et al 2008).…”

“…Particle number concentration (PNC) is assumed to be dominated by particles ≤100 nm, which could comprise more than 75% of total PNC (Evans et al 2014;Iskandar et al 2012). Thus, two-thirds of recent studies investigated UFP exposure using PNC within the size range up to 3,000 nm (Ohlwein et al 2019). However, recent studies have reported that exposure to particles in the accumulation mode (100-800 nm) could also be associated with daily cardiovascular mortality (Hennig et al 2018;Meng et al 2013), morbidity (Andersen et al 2008;Braniš et al 2010;Rosenthal et al 2013), and subclinical outcomes (Chen et al 2015;Han et al 2016;Sun et al 2015).…”

“…Previous epidemiological studies have found that PSC and particle length concentration (PLC) were more closely associated with daily mortality and inflammatory blood markers than PNC (Hennig et al 2018;Rückerl et al 2016). Thus, to improve the investigation of UFP-related health effects and to determine whether other particle metrics besides particulate matter (PM) with an aerodynamic diameter 2:5 lm PM 2:5 impact public health, there is an urgent need to explore alternative metrics and different size ranges, including particles >100 nm (Baldauf et al 2016;Ohlwein et al 2019).…”

Ambient Air Quality in the Czech Republic: Past and Present

“…The heavy air pollution in this region results from several major sources, such as traditional steel and coke plants, local heating (with common burning of waste or coal powder) and traffic and, last but not least, by regional transport of polluted air masses from industrial parts of Poland [137][138][139][140][141][142][143]. Industry is apparently the major source of ultrafine particles (UFP) [144,145], the aerosol fraction which is blamed for the strongest effects on human health [146].…”