cooperation with environ-
mental and health policy
Ultra ne particles - too small to see, too big to ignore:
What can regional and European environmental and health
policy do?
Summary for Policymakers and Stakeholders
Inhalable particles:
Upper airway and nasal cavities
(PM with a diameter < 10 μm)
Fine particles:
Lower airways and alveoli
(PM with a diameter < 2.5 μm)
Ultrafine particles:
Alveoli and translocation
into the blood
adapted from
Kreyling, W.G., Semmler-Behnke, M., Möller,
W. (2006): Health implications of nanoparticles.
Journal of Nanoparticle Research 8, 543–562.

Ultrafine particles (UFP) are the smallest constituents
of airborne particulate matter: they are smaller than
0.1 micrometres and invisible to our eyes (F1). Yet,
their potential adverse effects on human health are
of great concern because of their specific properties
and acting mechanisms (B1). Size governs the trans-
port and removal of particles from the air and their
deposition within the respiratory system and it is
partly associated with the chemical composition and
the source. UFP have little mass but high number and
surface area concentration and a high content of ele-
mental and organic carbon. Ambient UFP are built
from gases or originate from combustion processes.
In urban areas, they are emitted mostly by anthro-
pogenic sources like traffic, domestic heating, and
industrial processes. Epidemiological studies have
shown that particulate matter (PM) is associated
with adverse health effects¹, especially in vulnerable
population groups (F2). The health effects of UFP
are in part different from the effects of larger par-
ticles such as PM2.5 or PM1 2. However, evidence
on short-term health effects of UFP is still limited.
No epidemiological studies of long-term exposures to
ambient UFP have been conducted yet.
0.01 μm
0.05 μm
0.5 μm
5 μm
50 μm
0.1 μm
1.0 μm
10 μm
100 μm
Limit of
Thoracic particles
Fine particles
) Ultra ne particles
Invisible to our eyes, but detrimental to our health -
Why it is important to measure ultrafine particles (UFP)?
UFP 1-3-4
• deposit deeply in the lung.
• are not well recognized and cleared by the
immune system in the alveolar space.
• injure cells, cause oxidative stress,
inflammation, mitochondrial exhaustion,
and damage to protein and DNA.
• penetrate the lung membranes, reach the
bloodstream and can be transported to different
organs such as heart, liver, kidneys and brain.
• reach the brain via the olfactory nerve.
¹ Rückerl, R., Schneider, A., Breitner, S. et al. (2011): Health Effects of Particulate Air Pollution - A Review of Epidemiological Evidence. Inhalation
Toxicology 23(10), 555 - 592.
2 WHO Regional Office for Europe (2013): Review of evidence on health aspects of air pollution – REVIHAAP project. Technical report. Copenhagen,
Denmark (available at:;
22 October 2014)
³ Brook, R.D., Franklin, B., Cascio, W. et al. (2004):Air pollution and cardiovascular disease –
A statement for healthcare professionals from the expert panel on population and prevention science of the American Heart Association. Circulation
109, 2655-2671
4 Health Effects Institute (HEI) (2013): Understanding the Health Effects of Ambient Ultrafine Particles, HEI Review Panel on Ultrafine Particles, HEI
Perspectives 3, Insights from HEI’s research, Boston, USA (available at:;
accessed 5 November 2014)
adapted from Rückerl et al., 2001 1

The UFIREG project
The project “Ultrafine particles – an evidence based
contribution to the development of regional and Eu-
ropean environmental and health policy” (UFIREG)
aimed to improve the knowledge base on possib-
le health effects of ultrafine particles and to raise
overall awareness of environmental and health care
authorities and the population. Five cities in four
European countries participated in the study (F3).
ded in December 2014. It was implemented
through the CENTRAL EUROPE Programme,
co-financed by the ERDF.
The project was structured in two main areas:
Assessment of exposure to UFP and other air
pollutants in five European cities:
To investigate the
exposure of the population to UFP, UFIREG partners
have established standardised UFP measurements
in five cities. Based on the data generated through
UFIREG measurements, they have determined the
temporal variation of these very small particles in
each study location and performed a comprehensive
comparison on the air pollution situation between
the cities. Whereas the main focus lied on the imple-
mentation and harmonisation of UFP measurements
in the project cities as a basis for epidemiological
dies, it also aimed to develop long-term strategies for
regular measurements of UFP.
Epidemiology of short-term health effects:
analyses have assessed the short-term effects of these
particles on human mortality and morbidity, espe-
cially in relation to cardiovascular and respiratory
Ultrafine Particles – an evidence based contribution
to the development of regional and European envi-
ronmental and health policy (UFIREG)
Project number: 3CE288P3
Duration: 7/2011 – 12/2014
cooperation with environ-
mental and health policy

How variable is the exposure in the five UFIREG cities?
To investigate the exposure of the population to UFP,
UFIREG partners have established standardised UFP
measurements using custom-made mobility particle
size spectrometers in five cities located in Germa-
ny (Augsburg and Dresden), the Czech Republic
(Prague), Slovenia (Ljubljana) and Ukraine
nivtsi) (F4). All of the UFIREG measurement stations
were located at an urban or suburban background site
which was representative for a large part of the ur-
ban population and had no roads with heavy traffic in
immediate vicinity. To achieve high and comparable
data quality, UFIREG established an extensive quality
assurance program.
Selected Results
The temporal variation of UFP was determined at one
fixed monitoring site in each of the five project cities.
Overall, the particle number concentration (PNC)
of 10-100 nm particles varied between the five cities
from May 2012 to April 2014 (F5). In summer, there
was a considerable influence of new particle formati-
on due to high global radiation and precursor gases,
especially in Dresden and Prague. The results de-
monstrate that PNC in urban areas strongly depends
on various factors such as meteorological conditions,
cityscape and the activity of different particle sources
(traffic, domestic heating, long-range transport, etc.)
whereby the everyday life of people plays an impor-
tant role.
The deviance (+/- 20%) due to the PNC measurement
principle in general is larger than for other air pollu-
tion measurements. For epidemiological studies, the
deviance needs to be continuously monitored. De-
termination of the total PNC could be an alternative
for UFP measurements. However, the information of
size-resolved PNC data has an additional value for
defining sources of air pollution and human exposure
Appropriate instru-
ments show particle
number size distri-
butions, which means
they indicate how
many particles of a
defined size between
10 and 800 nm are in
one cubic centimetre
air at a certain time.
The function of the
instrument is based
on charging particles,
followed by segregati-
on of particles in an
electrical field accor-
ding to their diameter
and charge. In a last
step, the classified
particles are counted
by a particle counter.
High quality measurements of size-resolved PNC and
integration into routine monitoring networks are still
a challenge.

What is the evidence for health effects in the five UFIREG cities?
Epidemiological studies in the frame of the UFIREG
project have assessed the short-term effects of UFP on
human mortality and morbidity, especially in relation
to cardiovascular and respiratory diseases (B2).
Official statistics were used to determine the associ-
ation between air pollution concentration and daily
(cause-specific: respiratory and cardiovascular) hos-
pital admissions and mortality. Associations of UFP
levels and health effects were analyzed for each city
by use of Poisson regression models adjusting for a
number of confounding factors, such as time trend,
day of the week, holiday, vacation periods, influen-
za epidemics, air temperature and relative humidity.
Time lags were included to identify immediate effects
(2-day average: lag 0-1), delayed effects (average of lag
2-5) and prolonged effects (6-day average: lag 0-5).
City-specific effect estimates were pooled using meta-
analyses methods.
Selected Results
Results on morbidity and mortality effects of UFP
are heterogeneous across the five European cities
investigated. Overall, an increase in respiratory
hospital admissions and mortality can be detec-
ted for increases in UFP concentrations (F6, F7).
Results on cardiovascular health were less conclu-
sive. Although there is a growing body of scientific
literature that addresses the health effects related to
UFP (and UFIREG helped improving the knowledge
base for the impact of traffic emissions on health), it
is not sufficient to draw definite conclusions about the
specific health consequences of exposure to UFP.
There is still (a) limited epidemiological evidence on
the effect of short-term exposure to ultrafine particles
on health; (b) insufficient understanding of whether
the effects of UFP are independent of those of PM₂.₅
and PM₁₀; (c) no evidence on the effects of long-term
exposure to UFP on health, and (d) little evidence
showing which size ranges or chemical characteristics
of UFP are most significant to health5.
⁵WHO Regional Office for Europe (2013): Review of evidence
on health aspects of air pollution – REVIHAAP project. Technicalreport.
Copenhagen, Denmark (available at:
version.pdf; accessed 22 October 2014)
Chernivtsi was excluded from the analysis due to
insufficient respiratory death cases in 2013.

Where do we go from here? -
What can environmental and health policymakers contribute?
So far, no directives for the regulation of UFP in am-
bient air and almost no official measurements sites
which routinely measure UFP exist. Usually, research
results are used to formulate recommendations and
guidelines, e.g. the WHO Air Quality Guidelines⁶,
which support policymakers in setting thresholds of
air pollution constituents for national and European
policy on air quality control such as the EU Air Qua-
lity Directive⁷.
Current data and studies on the levels of UFP and
their health effects do not allow firm conclusions on
exposure limits and respective health effects to be
considered in European air quality guidelines. On the
other hand, to date, UFP are not included in routine
measurements of air quality monitoring stations. This
in turn explains the lack of data for epidemiological
At this stage, policymakers and stakeholders are
called upon for supporting routine measurements
and research efforts to resolve this chicken-egg
situation (B3).
Continue efforts to routinely monitor UFP and generate data for epidemiological studies:
Larger and more specific multi-centre studies and long study periods are needed to produce
powerful results. The creation of so-called supersites or special sites should be considered⁸.
Support multi-pollutant approaches as so far pollutants are mostly assessed
Foster the conduct of epidemiological studies to assess the association between UFP levels
and adverse health effects; concentration–response functions need to be established for
UFP and for newly identified health outcomes. This will also require the generation of large
data sets on these exposure metrics ⁸.
Facilitate studies for evidence that may allow defining limit values for daily concentrations
of UFP.
Develop and implement measures to reduce UFP emissions, particularly from transport and
domestic heating/biomass burning. Measures may include:
✓ Encourage mass public transit and alternative energy sources for vehicles
(electric and hybrid technologies)
✓ Encourage fewer road traffic journeys and more physically active transport
✓ Support concept of low emission zones (incl. shipping traffic in cities)
✓ Support urban planning measures that help control hot spots such as near road
✓ Support reliable filter systems for heavy duty vehicles
(construction machinery), ships, heating systems.
Help protect people from UFP and soot particles also at occupational sites
(e.g. construction sites).
Strengthen communication and awareness raising for professionals and the public in
relation to air pollution and particulate matter, including UFP.
What policymakers and stakeholders can contribute

⁶ WHO (2005): Air quality guidelines, global update 2005. Geneva, Switzerland (available at:
file/0005/78638/E90038.pdf?ua=1; accessed 23 October 2014)
⁷ European Commission (2008): Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality
and cleaner air for Europe (available at:;
accessed 27
October 2014)
⁸ WHO Regional Office for Europe (2013): Review of evidence on health aspects of air pollution – REVIHAAP project. Technical report. Copenha-
gen, Denmark (available at:;
accessed 22 October 2014)
The project consortium is suggesting
to further pursue open research
questions (B4):
Are the short-term health effects of UFP
comparable in cities across Europe?
(more multicentre time-series studies
including meta-analysis are needed)
What are the health effects of personal
short-term exposures to UFP?
What are the health effects of pollutant
mixtures and together with individual
activities i.e. in a tunnel or during
physical activity?
Are the health effects of UFP independent
of the health effects of black carbon
and/or other criteria air pollutants?
What are the long-term health effects of
UFP and their components?
Are population groups spending more
time near traffic more at risk compared to
other groups?
How effective are measures
implemented for increasing air quality
in urban settings?
Which are the main sources of UFP and
how to estimate the health effect impact
of specific UFP sources?
For further details please consult the UFIREG handbook and other documents on the UFIREG webpage at:
On this webpage you also find a link to a film explaining the background to the
UFIREG project.

Technische Universität Dresden
Research Association Public Health
Saxon State Office for Environment,
Agriculture and Geology
Helmholtz Zentrum München –
German Research Center
for Environmental Health (GmbH)
Institute of Experimental Medicine
Czech Hydrometeorological Institute
National Laboratory of Health,
Environment and Food
L.I.Medved‘s Research Center of
Preventive Toxicology, Food and
Chemical Safety, Ministry of Health,
Ukraine (State enterprise)
The UFIREG project is implemented through the CENTRAL EUROPE
Programme co-financed by the ERDF
Prepared and edited by the UFIREG Project Team.
Dr. A. Schneider (Helmholtz Zentrum München – German Research Center for Environmental Health (GmbH)) and Dr. S. Bastian
(Saxon State Office for Environment, Agriculture and Geology)
Dr F. Matthies, Environment & Health Consultancy, Feldafing
Graphic Design:
Laußer Konzepte, Daniela Laußer, Tutzing
Photos: Cover: fotolia/decade3D; S.3: fotolia/vbaleha; S.4:
Gunter Löschau (LfULG); S.5: fotolia/kara; S.6: fotolia/anatolii; S.7: fotolia/
alliance, fotolia/connel_design
© UFIREG Project 2014