Study designs for air pollution adverse health effects

Inquinamento atmosferico e
salute dei bambini
Claudia Galassi
Inquinamento atmosferico e salute dei
bambini
Di cosa parliamo….
- Le conoscenze sugli effetti sulla salute
dell’inquinamento atmosferico da traffico
veicolare
- Aspetti metodologici
- Disegno degli studi
- Esposizione
- Outcomes
Inquinamento atmosferico e salute dei
bambini
Di cosa non parliamo….
- Effetti di alcune specifiche esposizioni (es.
Piombo, Mercurio, inquinanti indoor)
- Politiche per la salute e sviluppo sostenibile
From
http://www.epa.gov/oar/oaqps/eog/course422/ap3.html
Particulate matter - definitions
A complex mixture of airborne solid and liquid
particles, including soot, organic material,
sulfates, nitrates, other salts, metals, biological
materials.
•
•
•
•
PM 10 -- inhalable particles
PM2.5 -- fine particles
PM10-PM2.5 -- coarse particles
PM 0.1 -- ultrafine particles
• ACUTE health effects (e.g. asthma
attacks, myocardial infarction, acute
bronchitis, death..)
• CHRONIC health effects (e.g. chronic
bronchitis, lung cancer, anticipation of
death...)
Aspetti metodologici
Weaknesses of experimental
studies
• a small number of, usually healthy, adult
volunteer subjects (generalisability of
results to the general population may be
difficult)
• “mix” of pollutants difficult to reproduce
• chronic effects (ex. cancer) cannot be
addressed
Types of studies for air pollution
• Animal studies
• Human studies
– Experimental (chamber studies)
– Epidemiological (or observational)
•
•
•
•
•
Cross-sectional
Case-control
Panel studies
Cohort
Time series
Volume fraction of BrdU-positive AS
nuclei in vessels (X10-2 %)
PM and progression of atherosclerosis
(rabbits model)
4
3
2,7
2
PM10
Control
1,6
1
0,7
0,6
0
n=9
n=5
Coronary arteries
n=9
n=6
Aorta
Suwa et al, 2002
Ambient Air Pollution and Atherosclerosis
in Los Angeles
Kunzli et al, EHP 2005 (free access)
carotid intima-media thickness (CIMT), a measure of subclinical atherosclerosis
Exposure Assessment
1. Individual exposure monitoring extremely
expensive and complex
From: cleanairinitiative.org/portal/system/files/presentations/72526_apph.pdf
Exposure Assessment
1. Individual exposure monitoring extremely
expensive and complex
 Proxy of exposure (ex. Questionnaires)
Exposure Assessment
2. Generally from fixed site ambient monitors; the
best options when large numbers exposed
–
Recent modelling techniques: LUR Models,
Dispersion Models, both based on GIS
Types of studies for air pollution
• Animal studies
• Human studies
– Experimental (chamber studies)
– Epidemiological (or observational)
•
•
•
•
•
Cross-sectional
Case-control
Panel studies
Cohort
Time series
Med J Aust. 1998 Nov 2;169(9):459-63.
Outdoor air pollution and children's
respiratory symptoms in the steel cities
of New South Wales.
Lewis PR, Hensley MJ, Wlodarczyk J,
Toneguzzi RC, Westley-Wise VJ, Dunn T,
Calvert D.
Open access
Objective:
To investigate the relationship between outdoor air
pollution and the respiratory health of children
aged 8 to 10 years
Methods:
A cross-sectional survey (between October 1993
and December 1993) of children's health and
home environment. Summary measures of
particulate pollution [PM10] and SO2 were
estimated for each area (using air quality
monitoring station data from July 1993 to June
1994).
Nine areas included.
Types of studies for air pollution
• Animal studies
• Human studies
– Experimental (chamber studies)
– Epidemiological (or observational)
•
•
•
•
•
Cross-sectional
Case-control
Panel studies
Cohort
Time series
Types of studies for air pollution
• Animal studies
• Human studies
– Experimental (chamber studies)
– Epidemiological (or observational)
•
•
•
•
•
Cross-sectional
Case-control
Panel studies
Cohort
Time series
Panel studies
• Panel of subjects keeping daily diaries (ex.
asthma diaries) (‘diary studies’)
• Exposures
– measured at the ecological level
– measured individually
• Outcomes
– measured at the individual level (not
necessarily with diaries)
Types of studies for air pollution
• Animal studies
• Human studies
– Experimental (chamber studies)
– Epidemiological (or observational)
•
•
•
•
•
Cross-sectional
Case-control
Panel studies
Cohort
Time series
Time Series Studies
• Recently proposed (late 1980s)
• Availability of advances in statistical
techniques and in computing technology
• Useful to investigate short term/acute
effects of air pollution
• Outcome and exposure are aggregated
over 1 day
O3
November 17 2004
Mortality
Time series studies
• Uses routinely collected data for both
exposure and outcome
• Outcomes studied can be: mortality,
hospitalisations, emergency department
admissions, GP visits
• Both exposure and outcome measured at
the ecological level
• Confounding: seasonal trends
Types of studies for air pollution
• Animal studies
• Human studies
– Experimental (chamber studies)
– Epidemiological (or observational)
•
•
•
•
•
Cross-sectional
Case-control
Panel studies
Cohort
Time series
Long-term health effects
Chronic exposure studies evaluate health end points
across communities or neighborhoods with different
levels of average pollution over longer time periods
(usually 1 year or more).
Pope CA, Environ Health Perspect 108(suppl 4):713-723 (2000).
Figure 3. Estimated Adjusted Mortality-Rate Ratios and Pollution Levels in the Six Cities.
Mean values are shown for the measures of air pollution. P denotes Portage, Wisconsin; T Topeka, Kansas; W Watertown,
Massachusetts; L St. Louis; H Harriman, Tennessee; and S Steubenville, Ohio.
Lung Cancer, Cardiopulmonary Mortality,
and Long-term Exposure to Fine Particulate
Air Pollution
C. Arden Pope III, PhD; Richard T. Burnett, PhD; Michael J.
Thun, MD; Eugenia E. Calle, PhD; Daniel Krewski, PhD;
Kazuhiko Ito, PhD; George D. Thurston, ScD
JAMA. 2002;287:1132-1141.
Methods
• 500,000 subjects, as Part of Cancer Prevention
II Study, enrolled in 1982
• Study population from 157 cities throughout the
USA (157 data points of exposure)
• Baseline questionnaire collected individual
information (age, sex, weight, height, smoking
history, etc)
• Subjects’ risk factors linked to air pollution data
and cause of death through to 1998
Birth cohorts
https://www.progettoninfea.it/
Criteria for assessing causality of associations
Strength of
association
Strong association considered to be more
likely causal than weak associations
Temporality
Exposure precedes effect
Specificity
A cause is associated with a single effect
Biologic gradient
An exposure-response relationship is
present
Plausibility
The association should be consistent with
relevant biologic data
Coherence
Experimental evid.
Hill (1965), Rothman (1986, 1998).
Effetti sulla salute
dell’inquinamento atmosferico
da traffico nei bambini
Effetti studiati:
• Patologie respiratorie
–Infezioni (alte /basse vie respiratorie)
–Asma (aggravamento/insorgenza)
• Esiti riproduttivi (nascite pre-termine)
• Tumori infantili
• Mortalità neonatale/infantile
Effetti respiratori acuti
Association of Low-Level Ozone and Fine
Particles With Respiratory Symptoms in
JAMA. 2003;290(14):1859-1867.
Children With Asthma
Design, Setting, and Participants Daily respiratory symptoms and medication use were
examined prospectively for 271 children younger than 12 years with physician-diagnosed, active
asthma residing in southern New England.
Main Outcome Measures Respiratory symptoms and rescue medication use recorded on
calendars by subjects' mothers.
Results Mean (SD) levels were 59 (19) ppb (1-hour average) and 51 (16) ppb (8-hour average)
for ozone and 13 (8) µg/m3 for PM2.5. In copollutant models, ozone level but not PM2.5 was
significantly associated with respiratory symptoms and rescue medication use among children
using maintenance medication; a 50-ppb increase in 1-hour ozone was associated with
increased likelihood of wheeze (by 35%) and chest tightness (by 47%). The highest levels of
ozone (1-hour or 8-hour averages) were associated with increased shortness of breath and
rescue medication use. No significant, exposure-dependent associations were observed for any
outcome by any pollutant among children who did not use maintenance medication.
Conclusion Asthmatic children using maintenance medication are particularly vulnerable to
ozone, controlling for exposure to fine particles, at levels below EPA standards.
Acta Paediatrica 2010
2007
Associations are
expressed as a
percentage change
(95% confidence
interval) in the
number of ER visits for
an increase of 10
ug/m3 in NO2, at
different lags (0–5),
Criteria for assessing causality of associations
Strength of
association
Strong association considered to be more
likely causal than weak associations
Temporality
Exposure precedes effect
Specificity
A cause is associated with a single effect
Biologic gradient
An exposure-response relationship is
present
Plausibility
The association should be consistent with
relevant biologic data
Coherence
Experimental evid.
Hill (1965), Rothman (1986, 1998).
coherence
•
•
•
•
•
symptoms
lung function decrease
GP visits/use of medications
ED presentations
hospital admissions
2005
The available evidence is also sufficient to
assume a causal relationship between
exposure to air pollution and aggravation of
asthma (mainly due to exposure to
particulate matter and ozone)
2005
A significant body of evidence supports the explanation
that much of the morbidity and mortality related to air
pollution in children occurs via interactions with
respiratory infections, which are very frequent among
children.
Evidence suggests a causal relationship
between exposure to ambient air pollution and
increased incidence of upper and lower
respiratory symptoms (many of which are likely
to be symptoms of infections).
Effetti sulla funzionalità polmonare
Gaudermann et al, NEJM 2004
Community specific proportion of 18 year old with a FEV1
below 80% of the Predicted Value Plotted against the
average levels of PM10 from 1994 through 2000.
Gaudermann et al, Lancet 2007
2005
Studies of lung function in children suggest that:
• living in areas of high air pollution is associated with lower
lung function;
• chronically elevated air pollution is associated with lower
rates of lung function growth;
• improvement in air pollution leads to improvements in
lung function level and/or growth rate;
• acute exposures to air pollution are associated with
apparently reversible deficits in lung function; and
• children who spend a significant amount of time outdoors
in polluted environments or those with poor nutrition may
be more strongly affected by air pollution.
2005
These effects of air pollution are modest, accounting for
only a few per cent of the deficit in average lung function.
Nevertheless, the studies suggest that the effects can be
cumulative over a 20-year growing period, and there is
uncertainty over whether the chronic effects are reversible.
Effetti cronici
Prevalenza Asma e Allergie
1980-1990: aumento medio 5% /anno
Prevalenza della rino-congiuntivite
allergica e del tasso di sensibilizzazione
1980-1990: aumento medio 14% / anno
aumento medio 6.7% /anno
ISAAC, The International Study of Asthma and Allergies in Childhood, is a unique
worldwide epidemiological research programme established in 1991 to investigate
asthma, rhinitis and eczema in children due to considerable concern that these
conditions were increasing in western and developing countries.
ISAAC has become the largest worldwide collaborative research project ever
undertaken, involving more than 100 countries and nearly 2 million children and its
aim is to develop environmental measures and disease monitoring in order to form the
basis for future interventions to reduce the burden of allergic and non-allergic
diseases, especially in children in developing countries.
The ISAAC findings to date have shown that these diseases are increasing in
developing countries and that they have little to do with allergy, especially in the
developing world. Further population studies are urgently needed to discover more
about the underlying mechanisms of non-allergic causes of asthma, rhinitis and
eczema and the burden of these conditions.
http://isaac.auckland.ac.nz/
ISAAC : International Study of Asthma
and Allergies in Childhood
Obiettivo: Stimare la prevalenza di asma ed allergie
nella popolazione di 6/7 anni e 13/14 anni, per
effettuare confronti geografici e temporali.
Metodo: 2 studi trasversali (campione casuale di
almeno 1000 bambini), a distanza di almeno 5 anni;
stesso protocollo d’indagine, questionari
standardizzati
http://isaac.auckland.ac.nz/
Condizioni considerate
•
•
•
•
•
•
Sibili (12 mesi)
Asma (nella vita)
Oculorinite (12 mesi)
Raffreddore primaverile (nella vita)
Segni di dermatite atopica (12 mesi)
Eczema (nella vita)
ISAAC core questions
• Sibili 12 mesi: "Have you had wheezing or
whistling in the chest in the past 12 months?“
• Oculorinite 12 mesi; "In the past 12 months, have
you had a problem with sneezing, or a runny, or a
blocked nose, accompanied by itchy and watery
eyes when you did not have a cold or the flu?"
• Dermatite atopica 12 mesi:“Have you had an itchy
rash, which was coming and going for at least 6
months at any time in the last 12 months, affecting
any of the following places: the folds of the elbows,
behind the knees, in front of the ankles, under the
buttocks, or around the necks, ears, or eyes?"
SIDRIA
Estensione italiana di ISAAC (International Study on
Asthma and Allergies in Childhood)
Fase 1 (ISAAC I): 1994/1995
Fase 2 (ISAAC III): 2002
Gruppo Collaborativo SIDRIA-2° fase
SIDRIA 2° fase
Cambiamenti nella prevalenza di asma e
allergie tra le due fasi dello studio
Gruppo Collaborativo SIDRIA-2° fase
Caratteristiche della popolazione
Bambini
94/95
2002
N° di aree
Adolescenti (self)
94/95
2002
6
6
8
8
Rispondenza
(%)
95,5
92,5
96,6
92,7
N° di soggetti
16 115
11 287
19 723
10 267
Genere
maschile (%)
51,8
51,3
52,2
52,5
Età (media)
6,4
6,7
13,1
13,3
Gruppo Collaborativo SIDRIA-2° fase
Cambiamenti nella prevalenza di fischi/sibili
negli ultimi 12 mesi per fasce di età
1994/95
%
2002
15
12
10,5
9
6
7,8
8,6
9,7
4,8
3
0
6-7 anni
13-14 (self)
5,3
13-14 (gen.)
Gruppo Collaborativo SIDRIA-2° fase
Cambiamenti nella prevalenza di asma
(nella vita) per fasce di età
1994/95
%
2002
15
12
9
12,1
9,1
9,5
10,4
10,6
9,1
6
3
0
6-7 anni
13-14 (self)
13-14 (gen.)
Gruppo Collaborativo SIDRIA-2° fase
Prevalenza di asma e sibili nei 12 mesi per
livello di urbanizzazione
Bambini (6-7 anni) – SIDRIA-2
Asma
15
10
Sibili
10,2
8,1
8,5
8,6
5
0
Metropoli
Altre aree
Cambiamenti nella prevalenza di raffreddore
primaverile (nella vita) per fasce di età
1994-95
2002
%
24
21
18
15
12
9
6
3
0
24,4
17,2
17,4
14,4
6,3
9
6-7 anni
13-14 (self)
13-14 (gen.)
Gruppo Collaborativo SIDRIA-2° fase
Cambiamenti nella prevalenza nella vita di
asma, raffreddore primaverile ed eczema nei
GENITORI di bambini di 6-7 anni
1994/95
35
30
30,1
25
20
21,5
15
10
5
2002
9,6
19,3
14,3
13,2
0
Asma
p < .05
Raff.prim.
Eczema
SIDRIA II
Analisi sensibilità
L’inclusione nel modello di analisi
di diversi fattori (istruzione della
madre, compilatore del
questionario, stagione di
rilevazione ) non cambia i risultati
in modo sostanziale.
In sintesi
La sintomatologia asmatica è invariata. La crescita
sembra essersi fermata
Modesto aumento della “diagnosi” di asma,
probabilmente in rapporto ad un maggior
riconoscimento della malattia
Rapido aumento dei sintomi di rinite allergica e della
diagnosi di raffreddore allergico nei bambini e nei
ragazzi
Rapido aumento dei sintomi di dermatite atopica e
della diagnosi di eczema nei bambini e nei ragazzi
ERJ 2001; 17:881
ERJ 2004; 23:407
BMJ 2004; 328:1052
-6.4
-3.4
-0.3
-2.2
-3.3
-4.8
BMJ 2004; 328:1052
+5.4
+2.6
+3.3
-3.4
BMJ 2004; 328:386
Allergy, 2004; 59:1301 –1307
L. García-Marcos et al.
Stabilization of asthma prevalence among adolescents and
increase among schoolchildren (ISAAC phases I and III) in
Spain.
In the last 8 years, the prevalence of asthma
has not changed in 13-14-year-old Spanish children
but has increased substantially in 6-7-year olds
Eur Resp J 2005, 26:647-650
The prevalence of asthma in children: a reversing
trend
C.P. van Schayck and H.A. Smit
The general practice registration showed that
after a five-fold increase in asthma prevalence
during the 1980s and 1990s a downward trend
seemed to occur around the turn of the century.
The public health service confirms a clear decrease
in wheezing and dyspnoea in children during the late
1990s.
Thus far, there has been no satisfactory
explanation for this observation.
Key findings di ISAAC Fase III
• Modesti cambiamenti della prevalenza totale dei
sintomi asmatici
– Riduzione della prevalenza di asma nei Paesi anglofoni
– Aumenti in alcuni (ma non in tutti) i Paesi dove
precedentemente la prevalenza dell’asma era bassa
– Aumenti della prevalenza in particolare in Africa,
America Latina e alcuni paesi asiatici
– Le differenze internazionali nella prevalenza dei
sintomi asmatici si sono ridotte
•Aumenti della prevalenza d’asma diagnosticata in
quasi tutti i Paesi
•L’asma non è più una malattia anglofona
La ricerca delle
cause dell’asma
Theories of asthma causation:
The “hygiene” hypothesis
Strachan, The British National Child Development
Study
• A lower exposure to infections in early
childhood is associated with an increased
risk of asthma and hay fever
• This could be occurring through a reduced
TH1 and an increased TH2 immune response
“L’ipotesi igienistica”
• L’aumento a livello globale nella prevalenza dell’asma
sarebbe attribuibile ad un aumento della suscettibilità
alla sensibilizzazione antigenica e/o allo sviluppo
dell’asma
• Tale aumento potrebbe essere dovuto al fatto che,
vivendo in ambienti domestici più puliti, abbiamo perso
l’effetto protettivo fornito in passato dalle infezioni
contratte in età infantile
• Questa ipotesi descrive meglio la distribuzione della
prevalenza dell’asma a livello globale
• Esistono però molte eccezioni: per esempio, la
prevalenza dell’asma è più alta in America Latina
(nonostante gli alti tassi di infezioni pediatriche) che
non in Spagna o in Portogallo.
Tutto è determinato prima della
nascita?
Eldeirawi K et al, J Allergy Clin Immunol 2005:
**Questionnaires with interview to parents of children
0-16 years old (NHANES-NHIS)
US-born Mexicans children were significantly more likely
to report asthma diagnosis than Mexico-born peers, after
accounting for potential confounding variables
Holguin F et al,Am J Resp Crit Care Med 2005:
**Questionnaires with interview (aged => 18 years)
in the language spoken in the household (NHANES-NHIS)
1) US-born Mexicans had a higher prevalence of asthma
than did Mexican-born Mexicans, independent to access
to health care and other potential confounders
2) With prolonged times of residence in the US, the
prevalence of asthma increased in Mexican-born
participants
less than 10yrs of residence = 2%,
more than 10yrs of residence = 4%
Results-1.
Prevalence of asthma and
wheezing by birthplace – SIDRIA II
CHILDREN
BORN IN
ITALY
Total
(N=28293)
CHILDREN
BORN OUTSIDE
OF ITALY
Total
(N=1012)
Total
(N=29305)
%
%
%
asthma
lifetime
last 12
months
9.7
5.4**
9.6
6.7
3.8**
6.6
wheeze
lifetime
last 12
months
25.0
15.8**
24.7
6.9
5.2*
6.8
*p<0.05, ** p<0.001 by 2 test
Results-2. Prevalence (%) of
asthma/wheezing by birthplace/parent origin
25
both italian
parents
one italian parent
20
both foreigners
parents
in Italy for >=5yrs
15
in Italy for < 5yrs
10
5
0
Lifetime
asthma
Asthma
last 12
months
Lifetime
wheeze
Wheeze
last 12
months
Considerazioni
1) I bambini e gli adolescenti nati all’estero
hanno una prevalenza significativamente più
bassa di asma e wheezing rispetto ai coetanei
nati in Italia.
Questi risultati sono consistenti con quelli di
altri studi che hanno evidenziato come i
bambini nati in Paesi più poveri abbiano una
minor prevalenza di asma.
Considerazioni
2) Tuttavia, la frequenza di asma e sintomi
asmatici dei bambini immigrati è risultata
diversa a seconda del tempo trascorso dalla
migrazione, mostrando un incremento del
rischio associato alla permanenza in Italia.
Anche questo dato è già stato segnalato in
letteratura, e suggerisce che i cambiamenti
nell’esposizione a fattori ambientali e
l’adozione di uno stile di vita occidentale
abbiano un ruolo predominante rispetto a
fattori genetici nello sviluppo dell’asma
nell’infanzia.
Considerazioni
3) Tutto questo sarebbe a supporto dell’ipotesi
secondo la quale nell’espressione della malattia
asmatica non giocano un ruolo primario solo i
primi anni di vita, ma possono essere rilevanti
anche i successivi cambiamenti nelle
esposizioni ambientali, come confermato anche
da alcuni studi di tipo occupazionale
Asthma epidemiology
The future
• Genetic factors cannot account for the
increase of asthma, but gene-environment
interactions may be important.
•
The search for environmental causes of
asthma is likely to continue to be primary,
while the study of gene-environment
interactions will play an important secondary
role
Pearce, 2001
Inquinamento atmosferico e
insorgenza dell’asma
(new onset asthma)
2005
There was little evidence for a causal
association between the
prevalence/incidence of asthma and air
pollution in general, though the evidence is
suggestive for a causal association between
the prevalence/incidence of asthma
symptoms and living in close proximity to
traffic.
Inquinamento atmosferico
e birth outcomes
2005
Overall, there is evidence implicating air pollution
in adverse effects on birth outcomes, but the
strength of the evidence differs between
outcomes.
The evidence is solid for infant mortality: this
effect is primarily due to respiratory deaths in the
post-neonatal period and it appears to be mainly
due to particulate air pollution.
2005
Overall, there is evidence implicating air pollution
in adverse effects on birth outcomes, but the
strength of the evidence differs between
outcomes.
Studies on birth weight, preterm births and IUGR
also suggest a link with air pollution, but there
were important inconsistencies in the results that
were probably due to differences in design and
measurement of exposure(s).
Ipotesi sui meccanismi
biologici plausibili
• Risposta infiammatoria
• Stress ossidativo
• Disfunzioni placentari
Inquinamento atmosferico e
tumori infantili
2005
Accumulated epidemiological evidence is
insufficient to infer a causal link between childhood
cancer and the levels of outdoor air pollution
typically found in Europe. However, the number of
available studies is limited and their results are not
fully consistent. Future studies, considering
exposure during different periods from conception
to disease diagnosis, may help to support a clearer
conclusion about the role of childhood exposures
to air pollution in causing cancers in both
childhood and adulthood.
Levels of evidence for causal relationships were defined as: (i) sufficient—at least one expert group has
reviewed the available evidence and published a peer-reviewed report indicating a consensus view that there is
a causal relationship, (ii) limited—evidence is suggestive of an association between the agent and the outcome
but is limited (and may or may not represent a causal relationship) because chance, bias and confounding
cannot be ruled out with confidence, e.g., at least one high-quality study shows a positive association but the
results of other studies are inconsistent and, (iii) inadequate—available studies are of insufficient quality (e.g.,
available studies have failed to adequately control for confounding or have inadequate exposure assessment),
consistency or statistical power to permit a conclusion regarding the presence or absence of an association or no
studies exist that examine the relationship.
Quali sviluppi di ricerca sugli effetti
dell’inquinamento atmosferico?
• Migliorare ( e standardizzare) le
metodologie di indagine per gli effetti
(soprattutto cronici) per i quali l’evidenza è
limitata
• Studi per migliorare le conoscenze sui
meccanismi d’azione
• Studi su effetti relativamente poco studiati
(es. effetti sullo sviluppo
neurocomportamentale del bambino)
Annual Cases (and %) attributed to Air Pollution
Austria, France, and Switzerland
Künzli et al, Lancet 2000; 356: 795-801
Outcome
Death (adults  30yrs.)
Hospital Admissions
(cardio-respiratory causes)
Chronic Bronchitis
(incidence in adults)
Bronchitis Episodes
(children)
Restricted Activity
Days (adults)
Asthma attacks
Cases
Attribut. %
40‘600
~6 %
(24‘600-56'900)
48’000
(17’300–79’100)
47'100
(4’300-93'500)
543'000
(239’500-981'600)
30.5 mill.
(25.7-37.3 mill)
1.04 mill.
(0.54–1.54 mill.)
~2%
~ 12 %
~ 30 %
~ 12 %
~6%