AIR POLLUTION AND ASTHMA EMERGENCY ROOM VISITS IN RENO, NEVADA

Particulate matter and emergency visits for asthma: a time-series study of their association in the presence and absence of wildfire smoke in Reno, Nevada, 2013-2018

BACKGROUND

Health risks due to particulate matter (PM) from wildfires may differ from risk due to PM from other sources. In places frequently subjected to wildfire smoke, such as Reno, Nevada, it is critical to determine whether wildfire PM poses unique risks. Our goal was to quantify the difference in the association of adverse asthma events with PM on days when wildfire smoke was present versus days when wildfire smoke was not present.

METHODS

We obtained counts of visits for asthma at emergency departments and urgent care centers from a large regional healthcare system in Reno for the years 2013-2018. We also obtained dates when wildfire smoke was present from the Washoe County Health District Air Quality Management Division. We then examined whether the presence of wildfire smoke modified the association of PM_2.5, PM_10-2.5, and PM₁₀ with asthma visits using generalized additive models. We improved on previous studies by excluding wildfire-smoke days where the PM concentration exceeded the maximum PM concentration on other days, thus accounting for possible nonlinearity in the association between PM concentration and asthma visits.

RESULTS

Air quality was affected by wildfire smoke on 188 days between 2013 and 2018. We found that the presence of wildfire smoke increased the association of a 5 μg/m³ increase in daily and three-day averages of PM_2.5 with asthma visits by 6.1% (95% confidence interval (CI): 2.1-10.3%) and 6.8% (CI: 1.2-12.7%), respectively. Similarly, the presence of wildfire smoke increased the association of a 5 μg/m³ increase in daily and three-day averages of PM₁₀ with asthma visits by 5.5% (CI: 2.5-8.6%) and 7.2% (CI: 2.6-12.0%), respectively. We did not observe any significant increases in association for PM_10-2.5 or for seven-day averages of PM_2.5 and PM₁₀.

CONCLUSIONS

Since we found significantly stronger associations of PM_2.5 and PM₁₀ with asthma visits when wildfire smoke was present, our results suggest that wildfire PM is more hazardous than non-wildfire PM for patients with asthma.

Air quality and emergency pediatric care for symptoms of bronchial obstruction categorized by age bracket in Rio de Janeiro, Brazil

The objective of this study was to estimate the association between levels of air pollutants and respiratory symptoms in children. An ecological time-series study was conducted between April 2002 and March 2003 with daily data on PM10, SO2, CO, NO2, and O3 and paediatric care in emergency rooms due to symptoms indicating bronchial obstruction. The potential confounding factors considered were: time trend, seasonality, meteorological variables, respiratory infections and the effects of weekends and holidays. A semi-parametric Poisson regression was used to model the time series. Splines (data smoothing functions), indicator variables and cubic polynomials were used to adjust the effects of the confounding variables. A 5% significance level was adopted for the study. A statistically significant increase of 6.7% in paediatric visits of children of less than 2 years of age was associated with PM10. A 3% positive association with O3 showed borderline significance (p < 0.06) in this age bracket. Our findings highlight the existence of an acknowledged public health problem in Rio de Janeiro, Brazil, and also emphasize the need to identify the principal sources of air pollutants.

Air pollution and hospital admissions for asthma in a tropical city: Kaohsiung, Taiwan

This study was undertaken to determine whether there is an association between air pollutants levels and hospital admissions for asthma in Kaohsiung, Taiwan. Hospital admissions for asthma and ambient air pollution data for Kaohsiung were obtained for the period from 1996 through 2003. The relative risk of hospital admission was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. In the single-pollutant models, on warm days (> or = 25 degrees C) statistically significant positive associations were found in all pollutants except sulfur dioxide (SO2). On cool days (< or = 25 degrees C) all pollutants were significantly associated with asthma admissions For the two pollutant models, CO and O3 were significant in combination with each of the other four pollutants on warm days. On cool days NO2 remained statistically significant in all the two-pollutant models. This study provides evidence that higher levels of ambient pollutants increase the risk of hospital admissions for asthma.

Air pollution and hospital admissions for asthma in a subtropical city: Taipei, Taiwan

This study was undertaken to determine whether there is an association between exposure to air pollutants levels and number of hospital admissions for asthma in Taipei, Taiwan. Hospital admissions for asthma and ambient air pollution data for Taipei were obtained for the period from 1996 through 2003. The relative risk of hospital admission for asthma was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. In the single-air-pollutant model, on warm days (> or = 25 degrees C) statistically significant positive associations were found for SO2, NO2, and CO levels with an increase in asthmatic admissions. On cool days (< 25 degrees C), all air pollutants were significantly associated with elevated asthma admissions except SO2. For the two-air-pollutant model, CO significantly increases hospital admissions for asthma in combination with each of the other four pollutants on warm days. On cool days, NO2 and O3 significantly elevated asthma rates in all the two-air-pollutant models. This study provides evidence that higher levels of ambient air pollutant concentrations increase the risk of hospital admissions for asthma.

Effects of Asian dust storm events on daily admissions for asthma in Taipei, Taiwan

In spring, windblown dust storms originating in the deserts of Mongolia and China make their way to Taipei city. These occurrences are known as Asian dust storm (ADS) events. The objective of this study was to assess the possible associations of ADS on the hospital asthma admissions of residents in Taipei, Taiwan, during the period 1996-2001. We identified 54 dust storm episodes, which were classified as index days. Daily asthma admissions on the index days were compared with admissions on the comparison days. We selected two comparison days for each index day, 7 days before the index days and 7 days after the index days. The effects of dust storms on asthma admissions were prominent 2 days after the event (8%). However, the association was not statistically significant. There may not have been enough power to detect associations resulting from the inadequate sample size of asthma admissions on ADS events days. However, it seems worthwhile to pay more attention to the ADS events and health in the future.

Air pollution and health effects in northern Nevada

The issue of adverse health effects of ambient air pollution has been extensively studied and reported worldwide over the past two decades. The urban area of Reno and Sparks in northern Nevada is one of two major urban centers in Nevada; the other is Las Vegas. The northern area, which has undergone a rapid population growth in the last decade, has special geographic characteristics and air pollution patterns. We conducted environmental epidemiological studies spanning the 1990s. This report summarizes the evidence and discusses the findings in relation to other studies. Ambient air pollution levels, even when below federal standards, have a marked potential to impact human health adversely. Air pollution was associated with (1) emergency room visits for asthma; (2) hospitalization for chronic obstructive pulmonary disease; (3) hospitalization for cardio-vascular disease; (4) elementary school absenteeism; and (5) low birth weight, preterm birth, and other adverse birth outcomes.

The interaction between particulate air pollution and allergens in enhancing allergic and airway responses

Although the detrimental effects of air pollution on human health have been brought widely to public notice, it appears that less attention has been given to the potential role of toxic air pollutants in the induction of allergic conditions such as asthma, rhinoconjunctivitis, and atopic eczema. A number of large epidemiologic studies have shown that people exposed to intense motor vehicle traffic and its associated emissions are at major risk for allergic symptoms, reduced lung function, and increased sensitization to common airborne allergens. Several laboratory-based studies have demonstrated that particulate air pollutants emitted from motor vehicles can induce allergic inflammation, enhance IgE responses, and increase airway hyperresponsiveness, which could provide an underlying mechanism for the increasing prevalence of allergic diseases. This article reviews the evidence that supports the causative link between particulate air pollution and the sharp increase in the prevalence of type I allergies in developed countries.

Air particulate pollution and hospital admissions for chronic obstructive pulmonary disease in Reno, Nevada

This study assessed the association between ambient PM(10) pollution and daily hospital admissions for chronic obstructive pulmonary disease (COPD) in Reno-Sparks, Nevada, for the period 1990-1994. All three hospitals in the region were included. There was a total of 3115 admissions for COPD during this period. Daily ambient PM(10) values were available from one of seven air monitoring stations in this region. Weather variables including temperature and wind speed were also collected from this station. The daily average concentration of PM(10) was 36.55 microg/m(3). The generalized additive model (GAM) was used in the whole analysis. After adjusting for the effects of weather variables, day of week, seasons, and time trend, the results show that PM(10) is a statistically significant predictor for daily hospital admissions for COPD. The relative risk (RR) of hospital admissions for COPD for an interquartile increase (26.6 microg/m(3)) of the 24-h average level of PM(10) is 1.049 (95% CI 1.011-1.087).

Air pollution and asthma

Asthma is a disease syndrome that has captured a great deal of attention for several years. One of the perplexing aspects to asthma is that the prevalence is increasing in most industrialized countries. The reasons for this widespread increase are largely unknown. Another aspect of industrialization is the persistence of air pollution in urban areas. Because much air pollution is due to vehicles, no solution appears in sight. The topic of this article is the association between air pollution and various signs and symptoms of asthma. Air pollution is convincingly associated with many signs of asthma aggravation. These include pulmonary function decrements, increased bronchial hyperresponsiveness, visits to emergency departments, hospital admissions, increased medication use and symptom reporting, inflammatory changes, interactions between air pollution and allergen challenges, and immune system changes. With the exception of exposure to environmental tobacco smoke, common air pollutants have not been shown to cause asthma. It seems prudent for clinicians to counsel their patients about the potential risks of asthma aggravation from common outdoor air pollutants.