Table 2.
Epidemiologic Studies Examining Ultrafine Particles and Objective Respiratory Outcomes Among Children
| Author (Year) | Study Setting; Design; Population | UFP Definition (Measure) | Other Measured Pollutantsb | Source of Outcome Measure | Resultsb |
|---|---|---|---|---|---|
| Pekkanen et al. (1997) | Finland 1994; longitudinal study; 39 children aged 7–12 years with asthmac | 0.01–0.032 μm, 0.032–0.1 μm (central ambient monitor, electric aerosol spectrometer) | Black smoke, CO, NO, NO2, O3, particles 0.1–10 μm, PM2.5, PM10, SO2 | PEF (morning, evening) | No statistically significant associations reported for UFPs (lags 0–3 and 4-day average) and any PEF |
| Tiitanen et al. (1999) | Finland 1995; longitudinal study; 49 children aged 8–13 years with chronic respiratory symptomsd | 0.01–0.1 μm (central ambient monitor, electric aerosol spectrometer) | Black carbon, CO, NO2, O3, particles 0.1–1 μm, PM2.5, PM10, SO2, total suspended particles | PEF (morning, evening) | Evening PEF (1-day lag): β = −1.00, SE = 0.60, P < .10 No statistically significant association reported for UFPs (lags 0–3 and 4-day average) and morning PEF |
| Newcomb et al. (2012) | United States 2009; case-crossover study; 24 children aged 5–12 years with asthmae | 0.02–1 μm (indoor and outdoor air sampling near childrenf, PTrak™, TSI Inc.) | PM10 | eNO, FEV1, FEF25–75 | No statistically significant associations reported for UFPs and any outcomes assessedg |
| Buonanno et al. (2013) | Italy 2010–2011; cross-sectional study; 103 children aged 8–11 yearsh | 0.01–0.3 μm (personal 2-day monitor, NanoTracer, Philips) | None | eNO, FEF25–75 | UFP dosei and FEV1: β = −0.003, SD = 0.001, P = 0.02 UFP dosei and FEF25–75: β = −0.008, SD = 0.003, P = 0.004 UFP dosei and eNO among children with asthma or HDM allergyj: β = 0.04, P < .01 |
CO, carbon monoxide; eNO, exhaled nitric oxide; FEF25–75, forced expiration between 25% and 75% of vital capacity; FEV1, forced expiratory flow rate in 1 second; HDM, house dust mite; NO, nitric oxide; NO2, nitrogen dioxide; O3, ozone; PEF, peak expiratory flow rate; PM2.5, particulate matter ≤2.5 μm; PM10, particulate matter ≤10 μm; SD, standard deviation, SE, standard error; SO2, sulfur dioxide; UFP, ultrafine particle.
UFP exposure was measured using particle number concentration in all studies except Buonanno et al., which calculated daily alveolar and tracheobronchial deposited surface area dose.
No statistically significant associations between UFPs and respiratory health outcomes were obtained from models that controlled for other pollutants.
Defined as physician-diagnosed asthma or reported wheezing or “attacks of shortness of breath with wheezing” during the previous 12 months. Although Pekkanen et al., 1997 studied children from the same study population as Tiitanen et al., 1999, the earlier study restricted their analysis to data from children who “lived in the center of town” and completed >60% of their self-reported PEF daily diary.
At least 1 of the following (by parent report): recent wheeze or dry cough (apart from colds), recent attacks of shortness of breath with wheezing, or asthma ever diagnosed by a doctor.
Physician-diagnosed.
Investigators carried particle counters behind groups of study participants at the time of the study intervention (i.e., walking indoors or outdoors within the university where the study was conducted. Investigators reported that most children lived in the same neighborhood as this university.
Although the authors found no significant associations directly relating UFPs to respiratory outcomes (α = 0.1 in this pilot study), they reported that type of walking environment (indoor versus outdoor) significantly interacted with UFP number concentration in predicting FEF25–75 (indoor environment β = 0.01, SE = 0.007, P = .07). Lag structure was not reported.
Asthma prevalence in this sample was 16%.
Calculated daily alveolar and tracheobronchial deposited surface area dose, which accounted for alveolar and tracheobronchial surface area concentration of inhaled particles, time in each microenvironment, activity, and inhalation rate during each activity.
Assessed by skin prick testing.