Effect of nitrogen dioxide exposure on susceptibility to influenza A virus infection in healthy adults

Air pollution exposure, SARS-CoV-2 infection, and immune response in a cohort of healthcare workers of a large university hospital in Milan, Italy

Several studies have examined the possible relationship between air pollutants and the risk of COVID-19 but most returned controversial findings. We tried to assess the association between (short- and long-term) exposure to particulate and gaseous pollutants, SARS-CoV-2 infections, and immune response in a population of healthcare workers (HCWs) with well-characterized individual data. We collected occupational and clinical characteristics of all HCWs who performed a nasopharyngeal swab (NPS) for detecting SARS-CoV-2 at the Policlinico Hospital in Milan (Lombardy, Italy) between February 24, 2020 (day after first documented case of COVID-19 in our hospital) and December 26, 2020 (day before start of the vaccination campaign). Each subject was assigned daily average levels of particulate matter ≤10 μm (PM10), nitrogen dioxide (NO2), and ozone (O3) retrieved from the air quality monitoring station closest to his/her residential address. Air pollution data were treated as time-dependent variables, generating person-days at risk. Multivariate Poisson regression models were fit to evaluate the rate of positive NPS and to assess the association between air pollution and antibody titer among NPS-positive HCWs. Among 3712 included HCWs, 635 (17.1%) had at least one positive NPS. A 10 μg/m3 increase in NO2 average concentration in the four days preceding NPS was associated with a higher risk of testing positive [Incidence Rate Ratio (IRR) = 1.08, 95% confidence interval (CI): 1.01; 1.16)]. When considering a 1 μg/m3 increase in 2019 annual NO2 average, we observed a higher risk of infection (IRR: 1.02, 95%CI: 1.00; 1.03) and an increased antibody titer (+2.4%, 95%CI: 1.1; 3.6%). Findings on PM10 and O3 were less consistent and, differently from NO2, were not confirmed in multipollutant models. Our study increases the body of evidence suggesting an active role of air pollution exposure on SARS-CoV-2 infection and confirms the importance of implementing pollution reduction policies to improve public health.

The association between ambient pollutants and influenza transmissibility: A nationwide study involving 30 provinces in China

Background

The impact of exposure to ambient pollutants on influenza transmissibility is poorly understood. We aim to examine the associations of six ambient pollutants with influenza transmissibility in China and assess the effect of the depletion of susceptibles.

Methods

Provincial-level surveillance data on weekly influenza-like illness (ILI) incidence and viral activity were utilized to estimate the instantaneous reproduction number (R_t) using spline functions. Log-linear regression and the distributed lag non-linear model (DLNM) were employed to investigate the effects of ambient pollutants-ozone (O₃), particulate matter ≤2.5 μm (PM_2.5), particulate matter ≤10 μm (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and carbon monoxide (CO)-on influenza transmissibility across 30 Chinese provinces from 2014 to 2019. Additionally, the potential effects of the depletion of susceptibles and regional characteristics were explored.

Results

There is a significantly positive correlation between influenza transmissibility and five distinct ambient pollutants: PM_2.5, PM₁₀, SO₂, CO, and NO₂. On average, these ambient pollutants explained percentages of the variance in R_t: 0.8%, 0.8%, 1.9%, 1.3%, and 1.4%, respectively. Conversely, O₃ was found to be negatively associated with R_t, explaining 1.5% of the variance in R_t. When controlling for the effect of susceptibles depletion, the effects of all pollutants were more pronounced. The effects of PM_2.5, PM₁₀, CO, and SO₂ were higher in the eastern and southern regions.

Conclusions

Most ambient pollutants may potentially contribute to the facilitation of human-to-human influenza virus transmission in China. This observed association was maintained even after adjusting for variation in the susceptible population.

Impact of lockdown and crop stubble burning on air quality of India: a case study from wheat-growing region

The emergence of COVID-19 has brought the entire planet to a halt. Many countries, including India, were compelled to shut down most urban, industrial, social and other activities as a result of the pandemic. Due to a series of complete lockdowns imposed in India from March 24 to May 17, 2020, and state-wise local level restrictions afterward, have resulted in significant reduction of emissions of numerous atmospheric pollutants. The objective of this study is to analyse the change in concentration of various pollutants such as nitrogen oxide (NO₂), carbon monoxide (CO) and aerosol optical depth (AOD) due to lockdown and also to quantify the contribution of crop stubble burning to air pollution. The Sentinel-5P based NO₂ and CO observations for 2019 and 2020 and Moderate Resolution Imaging Spectroradiometer (MODIS)-based AOD observations for 2016-2020 were used for detecting the variations. The obtained results showed a significant decrease in NO₂ levels during various stages of lockdown. Small decrease in CO levels was observed across most part of the India. With a few exceptions, such as coastal and desert regions, there was a moderate decrease in AOD levels. Furthermore, to study the contribution of NO₂, CO and AOD from crop stubble burning, MODIS observations on active fire events were obtained from Visible Infrared Imaging Radiometer Suite (VIIRS). The burning of crop stubble increased NO₂ emissions by 22 to 80%. CO levels, on the other hand, have risen by 7 to 25%. A considerable variation in AOD was reported, ranging from 1 to 426%.

Analyzing the severity of coronavirus infections in relation to air pollution: evidence-based study from Saudi Arabia

COVID-19 is one of the major pandemics in history. It has caused various health problems to majority of countries in the world. Several researchers have examined and developed studies regarding concerns on air pollution being considered a major risk factor causing respiratory infections. Such infections are carried out by microorganisms, thus further affecting the immune system. The present study involves the relationship between air pollutants and the total COVID-19 infections along with the estimation of death rates in several regions of Saudi Arabia. The major goal of this study comprises the analysis of the relationship between air pollutants concentration, such as PM10, NO₂, CO, SO₂, and O₃, and the widespread outbreak of COVID-19. This scenario involves the transmission, number of patients, critical cases, and death rates. Results show that the estimation of recorded COVID-19 cases was in the most polluted regions; the mortality rate and critical cases were also more distinct in these regions than in other regions in Saudi Arabia. The finding of this study demonstrates a positive correlation between the mean values of PM10, NO₂, CO, and SO₂ pollutants. The results represent the significant relationship between air pollution resulting from a high concentration of NO₂ and COVID-19 infections and deaths. In addition, a null hypothesis of the relation between other pollutants and COVID-19 infections cannot be rejected. The study also indicates a significant correlation between the means of NO₂ and CO and the total number of critical cases. Negative correlations are obtained between the mean of O₃ and the total number of cases, total deaths, and critical case per cumulative days.

The impact of air pollution on COVID-19 pandemic varied within different cities in South America using different models

There is a rising concern that air pollution plays an important role in the COVID-19 pandemic. However, the results were not consistent on the association between air pollution and the spread of COVID-19. In the study, air pollution data and the confirmed cases of COVID-19 were both gathered from five severe cities across three countries in South America. Daily real-time population regeneration (R_t) was calculated to assess the spread of COVID-19. Two frequently used models, generalized additive models (GAM) and multiple linear regression, were both used to explore the impact of environmental pollutants on the epidemic. Wide ranges of all six air pollutants were detected across the five cities. Spearman's correlation analysis confirmed the positive correlation within six pollutants. Rt value showed a gradual decline in all the five cities. Further analysis showed that the association between air pollution and COVID-19 varied across five cities. According to our research results, even for the same region, varied models gave inconsistent results. For example, in Sao Paulo, both models show SO₂ and O₃ are significant independent variables, however, the GAM model shows that PM₁₀ has a nonlinear negative correlation with R_t, while PM₁₀ has no significant correlation in the multiple linear model. Moreover, in the case of multiple regions, currently used models should be selected according to local conditions. Our results indicate that there is a significant relationship between air pollution and COVID-19 infection, which will help states, health practitioners, and policy makers in combating the COVID-19 pandemic in South America.

SARS-CoV-2 infection, COVID-19 pathogenesis, and exposure to air pollution: What is the connection?

Exposure to air pollutants has been previously associated with respiratory viral infections, including influenza, measles, mumps, rhinovirus, and respiratory syncytial virus. Epidemiological studies have also suggested that air pollution exposure is associated with increased cases of SARS-CoV-2 infection and COVID-19-associated mortality, although the molecular mechanisms by which pollutant exposure affects viral infection and pathogenesis of COVID-19 remain unknown. In this review, we suggest potential molecular mechanisms that could account for this association. We have focused on the potential effect of exposure to nitrogen dioxide (NO2 ), ozone (O3 ), and particulate matter (PM) since there are studies investigating how exposure to these pollutants affects the life cycle of other viruses. We have concluded that pollutant exposure may affect different stages of the viral life cycle, including inhibition of mucociliary clearance, alteration of viral receptors and proteases required for entry, changes to antiviral interferon production and viral replication, changes in viral assembly mediated by autophagy, prevention of uptake by macrophages, and promotion of viral spread by increasing epithelial permeability. We believe that exposure to pollutants skews adaptive immune responses toward bacterial/allergic immune responses, as opposed to antiviral responses. Exposure to air pollutants could also predispose exposed populations toward developing COIVD-19-associated immunopathology, enhancing virus-induced tissue inflammation and damage.

Epidemiology of influenza in hospitalized children with respiratory tract infection in Suzhou area from 2016 to 2019

Influenza is a contagious respiratory disease and risks public health in China, and it has caused wide public concern in recent years. Immunocompromised patients, such as children and elderly people, suffer more severe influenza complication and some extreme cases are even life threatening. To identify the influenza characteristics and its correlation with various climatic and environmental pollution factors, we collected the reported influenza epidemic of hospitalized children in Children's Hospital of Soochow University from 2016 to 2019. Our results show that the main influenza virus subtypes are A/H1N1, A/H3N2, B/BV, and B/BY. We also identified the characteristics of the prevalent influenza virus subtypes in different months, seasons, years, and patients' age. Of all the influenza infected patients, the most susceptible groups are children over 3 to 5 years of age, and more cases are reported in winter than other seasons. We also found that influenza is also highly correlated with climatic and environmental pollution factors, and the autoregressive integrated moving average model is employed for the short-term influenza prediction in Suzhou city, which can provide scientific basis for the prevention and control of influenza and public health decision-making.

The dark cloud with a silver lining: Assessing the impact of the SARS COVID-19 pandemic on the global environment

The Severe Acute Respiratory Syndrome-Coronavirus Disease 2019 (COVID-19) pandemic caused by a novel coronavirus known as SARS-CoV-2 has caused tremendous suffering and huge economic losses. We hypothesized that extreme measures of partial-to-total shutdown might have influenced the quality of the global environment because of decreased emissions of atmospheric pollutants. We tested this hypothesis using satellite imagery, climatic datasets (temperature, and absolute humidity), and COVID-19 cases available in the public domain. While the majority of the cases were recorded from Western countries, where mortality rates were strongly positively correlated with age, the number of cases in tropical regions was relatively lower than European and North American regions, possibly attributed to faster human-to-human transmission. There was a substantial reduction in the level of nitrogen dioxide (NO₂: 0.00002 mol m^-2), a low reduction in CO (<0.03 mol m^-2), and a low-to-moderate reduction in Aerosol Optical Depth (AOD: ~0.1-0.2) in the major hotspots of COVID-19 outbreak during February-March 2020, which may be attributed to the mass lockdowns. Our study projects an increasing coverage of high COVID-19 hazard at absolute humidity levels ranging from 4 to 9 g m^-3 across a large part of the globe during April-July 2020 due to a high prospective meteorological suitability for COVID-19 spread. Our findings suggest that there is ample scope for restoring the global environment from the ill-effects of anthropogenic activities through temporary shutdown measures.

The short-term effects of air pollutants on influenza-like illness in Jinan, China

Background

There is valid evidence that air pollution is associated with respiratory disease. However, few studies have quantified the short-term effects of six air pollutants on influenza-like illness (ILI). This study explores the potential relationship between air pollutants and ILI in Jinan, China.

Methods

Daily data on the concentration of particulate matters < 2.5 μm (PM 2.5), particulate matters < 10 μm (PM10), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), carbon monoxide (CO), and ozone (O₃) and ILI counts from 2016 to 2017 were retrieved. The wavelet coherence analysis and generalized poisson additive regression model were employed to qualify the relationship between air pollutants and ILI risk. The effects of air pollutants on different age groups were investigated.

Results

A total of 81,459 ILI counts were collected, and the average concentrations of PM2.5, PM10, O₃, CO, SO₂ and NO₂ were 67.8 μg/m³, 131.76 μg/ m³, 109.85 μg/ m³, 1133 μg/ m³, 33.06 μg/ m³ and 44.38 μg/ m³, respectively. A 10 μg/ m³ increase in concentration of PM2.5, PM10, CO at lag0 and SO₂ at lag01, was positively associated with a 1.0137 (95% confidence interval (CI): 1.0083–1.0192), 1.0074 (95% CI: 1.0041–1.0107), 1.0288 (95% CI: 1.0127–1.0451), and 1.0008 (95% CI: 1.0003–1.0012) of the relative risk (RR) of ILI, respectively. While, O3 (lag5) was negatively associated with ILI (RR 0.9863; 95%CI: 0.9787–0.9939), and no significant association was observed with NO₂, which can increase the incidence of ILI in the two-pollutant model. A short-term delayed impact of PM2.5, PM10, SO2 at lag02 and CO, O3 at lag05 was also observed. People aged 25–59, 5–14 and 0–4 were found to be significantly susceptible to PM2.5, PM10, CO; and all age groups were significantly susceptible to SO₂; People aged ≥60 year, 5–14 and 0–4 were found to be significantly negative associations with O₃.

Conclusion

Air pollutants, especially PM2.5, PM10, CO and SO₂, can increase the risk of ILI in Jinan. The government should create regulatory policies to reduce the level of air pollutants and remind people to practice preventative and control measures to decrease the incidence of ILI on pollution days.

The Risk of Nitrogen Dioxide: What have we Learned from Epidemiological and Clinical Studies?

Nitrogen dioxide (NO2) is an oxidant gas which contaminates ambient air in many urban and industrial locations, and indoor air in homes with combustion appliances. The Environmental Protection Agency presently regulates NO2 in ambient air as a “criteria” pollutant. In spite of decades of laboratory, clinical, and epidemiological research, the health effects of NO2 exposure on humans are not well understood. The toxicological evidence suggests that increased susceptibility to infection, functional deficits from effects on airways, and deterioration of the status of persons with chronic respiratory conditions, including asthmatics, are of potential concern. This paper provides a perspective on the present evidence related to human health effects of NO2. It addresses methodological barriers that limit the available data; assesses the adequacy of the data for risk assessment; and proposes a research agenda to obtain needed information on the health effects of NO2.

Allergic diseases and air pollution

The prevalence of allergic diseases has been increasing rapidly, especially in developing countries. Various adverse health outcomes such as allergic disease can be attributed to rapidly increasing air pollution levels. Rapid urbanization and increased energy consumption worldwide have exposed the human body to not only increased quantities of ambient air pollution, but also a greater variety of pollutants. Many studies clearly demonstrate that air pollutants potently trigger asthma exacerbation. Evidence that transportation-related pollutants contribute to the development of allergies is also emerging. Moreover, exposure to particulate matter, ozone, and nitrogen dioxide contributes to the increased susceptibility to respiratory infections. This article focuses on the current understanding of the detrimental effects of air pollutants on allergic disease including exacerbation to the development of asthma, allergic rhinitis, and eczema as well as epigenetic regulation.

Modification by influenza on health effects of air pollution in Hong Kong

BACKGROUND

Both influenza viruses and air pollutants have been well documented as major hazards to human health, but few epidemiologic studies have assessed effect modification of influenza on health effects of ambient air pollutants.

OBJECTIVES

We aimed to assess modifying effects of influenza on health effects of ambient air pollutants.

METHODS

We applied Poisson regression to daily numbers of hospitalizations and mortality to develop core models after adjustment for potential time-varying confounding variables. We assessed modification of influenza by adding variables for concentrations of single ambient air pollutants and proportions of influenza-positive specimens (influenza intensity) and their cross-product terms.

RESULTS

We found significant effect modification of influenza (p < 0.05) for effects of ozone. When influenza intensity is assumed to increase from 0% to 10%, the excess risks per 10-microg/m(3) increase in concentration of O(3) increased 0.24% and 0.40% for hospitalization of respiratory disease in the all-ages group and >or= 65 year age group, respectively; 0.46% for hospitalization of acute respiratory disease in the all-ages group; and 0.40% for hospitalization of chronic obstructive pulmonary disease in the >or= 65 group. The estimated increases in the excess risks for mortality of respiratory disease and chronic obstructive pulmonary disease in the all-ages group were 0.59% and 1.05%, respectively. We found no significant modification of influenza on effects of other pollutants in most disease outcomes under study.

CONCLUSIONS

Influenza activity could be an effect modifier for the health effects of air pollutants particularly for O(3) and should be considered in the studies for short-term effects of air pollutants on health.

Personal exposure to nitrogen dioxide (NO2) and the severity of virus-induced asthma in children

BACKGROUND

A link between exposure to the air pollutant nitrogen dioxide (NO2) and respiratory disease has been suggested. Viral infections are the major cause of asthma exacerbations. We aimed to assess whether there is a relation between NO2 exposure and the severity of asthma exacerbations caused by proven respiratory viral infections in children.

METHODS

A cohort of 114 asthmatic children aged between 8 and 11 years recorded daily upper and lower respiratory-tract symptoms, peak expiratory flow (PEF), and measured personal NO2 exposures every week for up to 13 months. We took nasal aspirates during reported episodes of upper respiratory-tract illness and tested for infection by common respiratory viruses and atypical bacteria with RT-PCR assays. We used generalised estimating equations to assess the relation between low (<7.5 microg/m3), medium (7.5-14 microg/m3 ), and high (>14 microg/m3) tertiles of NO2 exposure in the week before or after upper respiratory-tract infection and the severity of asthma exacerbation in the week after the start of an infection.

FINDINGS

One or more viruses were detected in 78% of reported infection episodes, and the medians of NO2 exposure were 5 (IQR 3.6-6.3), 10 (8.7-12.0), and 21 microg/m3 (16.8-42.9) for low, medium, and high tertiles, respectively. There were significant increases in the severity of lower respiratory-tract symptom scores across the three tertiles (0.6 for all viruses [p=0.05] and >2 for respiratory syncytial virus [p=0.01]) and a reduction in PEF of more than 12 L/min for picornavirus (p=0.04) for high compared with low NO2 exposure before the start of the virus-induced exacerbation.

INTERPRETATION

High exposure to NO2 in the week before the start of a respiratory viral infection, and at levels within current air quality standards, is associated with an increase in the severity of a resulting asthma exacerbation.

Air pollution and infection in respiratory illness

The detrimental effects of air pollution on health have been recognized for most of the last century. Effective legislation has led to a change in the nature of the air pollutants in outdoor air in developed countries, while combustion of raw fuels in the indoor environment remains a major health hazard in developing countries. The mechanisms of how these pollutants exert their effects are likely to be different, but there is emerging evidence that the toxic effects of new photochemical pollutants such as nitrogen dioxide are likely to be related to infection. This review discusses the relationship between air pollution and infection and will explore some of the mechanisms of how both could act synergistically to cause respiratory illnesses especially in exacerbating symptoms in individuals with pre-existing respiratory conditions such as asthma and chronic obstructive pulmonary disease.

Exacerbations: etiology and pathophysiologic mechanisms

Some patients with COPD are prone to frequent exacerbations, which are an important determinant of health status. Such patients have elevated airway cytokine levels, suggesting the presence of increased inflammation that may increase their susceptibility to exacerbation. The inflammatory response during a COPD exacerbation is variable, but increases in interleukin-6 levels during the exacerbation are related to the presence of a common cold. Rhinovirus infection is the most important etiologic factor in COPD exacerbations and is an important target for preventive therapy. The reduction of COPD exacerbations will have an important impact on the considerable morbidity and mortality associated with COPD.

Nitrogen dioxide exposure: effects on airway and blood cells

This study examined the effects of nitrogen dioxide (NO(2)) exposure on airway inflammation, blood cells, and antiviral respiratory defense. Twenty-one healthy volunteers were exposed on separate occasions to air and 0.6 and 1.5 ppm NO(2) for 3 h with intermittent moderate exercise. Phlebotomy and bronchoscopy were performed 3.5 h after each exposure, and recovered cells were challenged with respiratory viruses in vitro. Blood studies revealed a 4.1% NO(2) dose-related decrease in hematocrit (P = 0.003). Circulating total lymphocytes (P = 0.024) and T lymphocytes (P = 0.049) decreased with NO(2) exposure. Exposure to NO(2) increased the blood lymphocyte CD4(+)-to-CD8(+) ratio from 1.74 +/- 0.11 to 1.85 +/- 0.12 in males but decreased it from 1.88 +/- 0.19 to 1.78 +/- 0.19 in females (P < 0.001 for gender difference). Polymorphonuclear leukocytes in bronchial lavage increased with NO(2) exposure (P = 0.003). Bronchial epithelial cells obtained after exposure to 1.5 ppm NO(2) released 40% more lactate dehydrogenase after challenge with respiratory syncytial virus than with air exposure (P = 0.024). In healthy subjects, exposures to NO(2) at levels found indoors cause mild airway inflammation, effects on blood cells, and increased susceptibility of airway epithelial cells to injury from respiratory viruses.

Influenza: vaccination and treatment

Few conditions exert such an enormous toll of absenteeism, suffering, medical consultations, hospitalization, death and economic loss as influenza. Patients at high risk of complications and mortality include the elderly and those with pre-existing cardiopulmonary disease. The outbreak in 1997 in Hong Kong, of avian H5N1 influenza in man, which resulted in six deaths among 18 hospitalized cases, and the recent isolation of H9N2 viruses from two children in Hong Kong, are reminders that preparation must be made for the next pandemic. Since the 1970s, efforts to control influenza have mostly focussed on the split product and surface antigen vaccines. These vaccines are of proven efficacy in healthy adults and are effective in elderly people with and without medical conditions putting them at high risk of complications and death following influenza infection. However, vaccine coverage is patchy and often low, and outbreaks of influenza are not uncommon in well-immunized residents of nursing homes. New vaccines and methods of vaccine delivery are being developed in attempts to overcome the limitations of existing vaccines. The antiviral drugs amantadine and rimantadine were developed in the 1960s, but have not been used widely due to their spectrum of activity, rapid emergence of resistance, and adverse effects associated with amantadine. The site of enzyme activity of the influenza neuraminidase is highly conserved between types, subtypes and strains of influenza and has emerged as the target of an exciting new class of antiviral agents that are effective both prophylactically and as therapy.

The nose versus the environment: 1982 and today

A brief overview of recent publications dealing with the effects of environmental pollutants on upper respiratory tract mucosa is presented. It mainly focuses on airborne irritants, substances inducing epithelial hyperplasia, metaplasia, and epithelial damage, and on inflammatory changes of nasal mucosa associated with environmental pollutants. Data from epidemiologic surveys, human exposure studies, animal experiments, and in vitro studies have improved present concepts of the significance of environmental pollutants for upper respiratory diseases. Although various national and international initiatives have resulted in a considerable reduction of indoor and outdoor pollutants within recent years, environmental pollutants continue to affect upper respiratory tract health of the population in urban areas and industrialized regions. Continuing efforts to reduce emissions of air pollutants are indispensable.

Inflammatory response in humans exposed to 2.0 ppm nitrogen dioxide

Nitrogen dioxide (NO2) is a common indoor air pollutant, especially in homes with unvented combustion appliances. Epidemiological studies suggest that children living in homes with unvented heating sources are more prone to respiratory infections than children living in homes with lower levels of NO2. However, experimental studies in which human volunteers were exposed acutely to moderate levels of NO2 (0.5-2.0 ppm) have shown little evidence of lung inflammation or decreased host resistance capacity. In the study reported here, 8 healthy volunteers were exposed to 2.0 ppm NO2 and to filtered air for 4 h while undergoing intermittent moderate exercise. Bronchoalveolar lavage was performed the following morning. The lavage was divided into a predominantly bronchial washing (first 20 ml of lavage; BL) and a predominantly alveolar washing (BAL). In the BL, NO2 exposure caused increases in polymorphonuclear neutrophils (PMNs), interleukin 6 (IL-6), IL-8, alpha1-antitrypsin, and tissue plasminogen activator, and decreases in epithelial cells. In the BAL, there were no NO2-induced changes in either cell numbers or soluble mediators. On the other hand, alveolar macrophages from BAL showed a decrease in the ability to phagocytose unopsonized Candida albicans and a decrease in superoxide production. No difference in susceptibility to virus infection was found between the NO2- and air-exposed macrophages. No changes in lung function were observed, but the aerosol bolus recovery technique revealed a statistically significant (p <.05) decrease in the fraction of aerosol recovered following nitrogen dioxide exposure, which is suggestive of small obstructive changes induced by NO2.

Risk factors for lower respiratory complications of rhinovirus infections in elderly people living in the community: prospective cohort study

OBJECTIVE

To assess the role of rhinoviruses in elderly people living in the community.

DESIGN

Prospective community based surveillance of elderly people, without intervention. Subjects were telephoned weekly to identify symptomatic upper respiratory tract infections. Symptoms and impact of illnesses were monitored, and specimens were collected for diagnostic serology and human rhinovirus polymerase chain reaction.

SETTING

Leicestershire, England.

SUBJECTS

533 subjects aged 60 to 90.

MAIN OUTCOME MEASURES

Symptoms, restriction of activity, medical consultations, and antibiotic use during 96 rhinovirus infections. Adjusted odds ratios for lower respiratory syndromes with respect to smoking and health status.

RESULTS

A viral cause was established in 211 (43%) of 497 respiratory illnesses; rhinoviruses were identified in 121 (24%) and as single pathogens in 107. The median duration of the first or only rhinovirus infection in the 96 people with 107 rhinovirus infections was 16 days; 18 of the 96 patients were confined to bed and 25 were unable to cope with routine household activities. Overall, 60 patients with rhinovirus infections had lower respiratory tract syndromes; 41 patients consulted their doctor, 31 of them (76%) receiving antibiotics. One patient died. Logistic regression analysis showed that chronic medical conditions increased the estimated probability of lower respiratory rhinovirus illness by 40% (95% confidence interval 17% to 68%) and smoking by 47% (14% to 90%). There were almost six times as many symptomatic rhinovirus infections as influenza A and B infections.

CONCLUSIONS

Rhinoviruses are an important cause of debility and lower respiratory illness among elderly people in the community. Chronic ill health and smoking increase the likelihood of lower respiratory complications from such infections. The overall burden of rhinovirus infections in elderly people may approach that of influenza.

Distribution and determinants of personal exposure to nitrogen dioxide in school children

OBJECTIVES

To assess the distribution of personal exposures to nitrogen dioxide (NO2) in school children, and to investigate factors that might influence personal exposure.

METHODS

NO2 exposures were assessed by use of passive diffusion tubes for 46 children aged 9-11 years, selected from two Southampton schools. The tubes were worn for seven days, and parallel measurements were made with static samplers in the child's kitchen, living room, classroom, and playground. Information about potential exposures was collected by questionnaire.

RESULTS

Personal exposures to NO2, averaged over seven days, ranged from 11 to 257 micrograms/m3 (6 to 137 ppb) with a geometric mean of 36 micrograms/m3 (19 ppb). Exposures correlated with concentrations of NO2 recorded in the home, but the relation was far from exact. Factors associated with increased personal exposure included the use of gas appliances in the home, living with one or more smokers, and travel to school by means other than a car. However, together these variables only explained a small part of the variation in personal exposures.

CONCLUSIONS

These findings reinforce the need for personal monitoring of exposure in studies investigating potential health effects of NO2 in children.

Characterization of upper respiratory disease in rats following neonatal inoculation with a rat-adapted influenza virus

Neonatal F344 rats were infected with a rat-adapted influenza virus (RAIV) to use as a potential model to study the combined effects of air pollutant exposure with early life respiratory viral infections. Initially, 6-day-old pups were intranasally inoculated with RAIV or medium alone, and nasal and lower respiratory tract (LRT) tissues were assessed histologically at 1, 3, 6, and 13 days postinoculation (DPI). Immunologic assessments included thymic lymphocyte quantification and anti-RAIV immunoglobulin production. Pups then received two inoculations (at 6 and 30 days of age), with histologic and immunologic assessment 6 and 13 days after the second inoculation and bronchoprovocation testing 5-8 weeks later. Following the single RAIV inoculation, IgM and IgG1 measurements increased at 6, 11, and 15 DPI, with IgG1 being greater at 11 and 15 DPI. Nasal lesions were evident as early as 1 DPI and primarily involved the anterior dorsal medial meatus and adjacent dorsal atrio- and nasoturbinates. Alterations included epithelial cell exfoliation and necrosis, mild erosions, suppurative and nonsuppurative inflammation, intraepithelial neutrophil accumulations, and intraluminal exudate. By 3 DPI, olfactory epithelial damage was multifocal or locally diffuse, with degeneration of sensory cells and variable inflammation. By 13 DPI, lesions were essentially repaired. Minimal changes were apparent in the LRT despite evidence of viral replication in the lungs 24 hours after inoculation (> 3 log10 plaque-forming units/lung). Pups reinoculated with RAIV at 30 days of age did not develop significant histologic lesions, nor did they exhibit increased airway responsiveness when assessed as young adults. In spite of their immature immune status at the time of initial infection, 13 days after the second RAIV inoculation, IgG1 increased substantially. Thus, neonatal RAIV infection resulted in acute nasal epithelial injury and inflammation, alterations that may allow subsequent evaluation of viral disease-air pollutant interactions.

Respiratory effects of pollution

Atmospheric pollution is increasingly responsible for chronic airway disease. Although outdoor pollution has decreased somewhat in recent years, indoor pollution has increased. Outdoor pollution results essentially from the combustion of coal and other fuels used for heating, industrial production and motor vehicles. The major sources of indoor pollution are heating and cooking devices. The main pollutants are suspended particulates, SO2, NO2 in indoor pollution and ozone which is linked to the photochemical effects. Transient increases in pollution cause transient decreases in pulmonary airflow. Chronic pollution seems to lead to an increase in the prevalence of lower and upper respiratory airway symptoms. In young children early exposure to pollution contributes to the development of chronic airways disease later in life. Asthmatics are at greater risk for pollution-related complications and several pollutants are known to increase bronchial reactivity. Further efforts are needed to reduce in pollution indoor and outdoor environments in particular with regard to tobacco smoke and especially for children.