Acute respiratory effects of particles: mass or number?

OBJECTIVES—To determine whether associations might be found, in patients with chronic airflow obstruction, between symptoms, peak flow rate (PEF), and particle mass and numbers, and to assess which measure was most closely associated with changes in health. Epidemiological studies have shown associations between particulate air pollution and cardiovascular and respiratory disease, and it has been proposed that these may be mediated by particles of nm size (ultrafine).
METHODS—Relations were investigated between symptom scores, PEF, and bronchodilator use in 44 patients aged 50 years with chronic obstructive pulmonary disease, and daily measurements of both mass of ambient particles of aerodynamic diameter less than 10 µm (PM₁₀) and numbers of ultrafine particles (<100 nm), allowing for meteorological variables. Symptom scores, bronchodilator use, and PEF were recorded daily for 3 months. Counts of ultrafine particles were made by the TSI model 3934 scanning mobility particle sizer (SMPS) and PM₁₀ measurements by the tapered element oscillating microbalance (TEOM).
RESULTS—Ultrafine particle counts indoors and outdoors were significantly correlated, those indoors being about half of those outdoors. No associations were found between actual PEF and PM₁₀ or ultrafine particles. However, there was a 19% increase in the rate of 10% decrements in daytime PEF with increases in PM₁₀ from 10 to 20 µg/m³ which was of borderline significance (p=0.05). A change in PM₁₀ from 10 to 20 µg/m³ was significantly associated with a 14% increase in the rate of high scores of shortness of breath (p=0.003). A similar change in PM₁₀ as a moving average of the same day and 2 previous days was associated with a 31% increase in the rate of high scores for cough (p=0.02). Cough symptoms were also associated with lower temperatures (p=0.02). Higher use of medicines was also associated with higher PM₁₀, but the increases were very small in clinical terms.
CONCLUSIONS—Evidence was not found to support the hypothesis that the component of particulate pollution responsible for effects on respiratory symptoms or function resides in the fraction below 100 nm diameter. The consistent associations between symptoms and PM₁₀ suggest that a contribution of the coarser fraction should not be dismissed. Further studies will be needed before the conclusions of this specific project may be generalised.


Keywords: air pollution; ultrafine particles; chronic obstructive lung disease     

What to do about softwood? A review of respiratory effects and recommendations regarding exposure limits

Wood dust has been classified as a human carcinogen by the International Agency for Research on Cancer with a footnote that the evaluation was based on a marked excess of sino-nasal cancer among workers exposed primarily to hardwood dusts. Because the epidemiologic data on the carcinogenic effects of softwoods are weaker than for hardwoods, standard setting for softwood dust presents a greater dilemma. Unfortunately, the studies of wood dust and cancer do not have the quantitative exposure data necessary for standard setting for either hardwoods or softwoods. Asthma, non-asthmatic airflow obstruction, and both upper and lower respiratory symptoms have been associated with exposure to both ‘allergenic’ and ‘non-allergenic’ softwood dusts, and an association with increasing intensity of exposure has been observed in multiple studies. The available evidence seems to indicate that to prevent these nonmalignant effects, the level of exposure to all softwood dust should be at least as low 2 mg/m³. A standard of 1 mg/m³ may be more appropriate to provide a safety margin to protect more sensitive workers. It may be that some of the health effects observed are due to the natural components of wood, such as resin acids or monoterpenes, or to molds. Am. J. Ind. Med. 31:385–398, 1997. © 1997 Wiley-Liss, Inc.     

Can We protect workers from developing the adverse respiratory effects of isocyanate exposure?

In this review, the authors have attempted to present the difficulty in defining a permissible exposure limit (PEL) to agents that act as sensitizers and may induce asthma-even at exposure levels less than the PEL. One approach to this relatively unaddressed problem may be to define the separate aspects of exposure to the specific sensitizing agent. The first effect is an accelerated rate of decline in lung function in nonsensitized individuals who are exposed to the agent (in this case the model used is isocyanates). The second effect is sensitization. Rules for developing a PEL might take this sensitizing effect into account, and this group of agents with such dual effects may be defined as "sensitizers." Exposure to agents with this designation would require special educational and surveillance initiatives to facilitate early detection. The elimination of sensitization may be a greater challenge. An important form of prevention is medical screening of exposed workers, yet it is unclear which screening approach best identifies workers with early isocyanate asthma.     

Child nutrition and growth: butterfly effects?

The international symposium organised by the Danone Institute as a pre-congress satellite of the European Nutrition Societies Congress, in Paris, in July 2007, brought together experts of child nutrition and behaviour. These experts coming from several countries of Europe and North America shared their views on the impact of numerous factors affecting child eating and health in present-day developed societies. Topics included nutritional influences during foetal life, early life development of food likes and dislikes, neophobia, ability for energy regulation, impact of media and advertisement, etc. Most contributions addressed the obesity epidemics and the problems associated with body weight control. Other aspects of child health were also considered, for example the nutritional challenge of adequately feeding children with type 1 diabetes. The nine speakers were asked to underline practical strategies to improve nutrition in early life, so as to maximise health, growth and quality of life in today's environment. The present paper is a summary of the ideas expressed by the experts, highlighting agreements, convergences, and occasional disagreements between expert opinions.     

Hormonal factors and risk of lung cancer among women?

BACKGROUND: Gender differences in the histological distribution of lung carcinoma and a possibly greater susceptibility of women than men to tobacco carcinogens, suggest a possible influence of sex-specific hormones. This study examines endocrine factors and risk of lung cancer among women by smoking status and histology. METHODS: We used data of a case-control study on lung cancer conducted from 1990 to 1996 in Germany, including 811 histologically confirmed female cases and 912 female population controls. Information on various menstrual and reproductive factors, use of oral contraceptives (OC), hormone replacement therapy (HRT), and smoking was gathered through personal interviews using a structured questionnaire. Odds ratios (OR) and 95% CI adjusted for age, region, smoking, and education were calculated via logistic regression. RESULTS: A reduction in lung cancer risk was observed with the use of OC (OR = 0.69; 95% CI: 0.51-0.92), but no trend in risk with increasing duration of use, age at first use, or calendar year of first use was present. A history of HRT was associated with a reduced risk (OR = 0.83; 95% CI: 0.64-1.09), particularly after long duration (>/=7 years) (OR = 0.59; 95% CI: 0.37-0.93). No clear association was found with regard to age at menarche, length of menstrual cycle, number of live-births, and age at menopause. Overall results did not differ much by histological cell subtype. The reduction in lung cancer risk associated with the use of exogenous hormones was primarily seen among smoking women. CONCLUSIONS: Our data provide evidence for a possible role of hormonal factors in the aetiology of lung cancer in women.     

Leanness and lung cancer risk: fact or artifact?

BACKGROUND: More than a dozen studies have examined the association between leanness and increased lung cancer risk. None of the prospective studies has been large enough to allow exclusion of smokers or persons with preexisting disease, two factors that cause both leanness and poor survival and thus may cause a spurious association between low body mass index and fatal lung cancer. METHODS: Using Cox proportional hazards models, we examined this issue in a cohort of 941,105 U.S. adults enrolled in an American Cancer Society prospective study in 1982. During 14 years of follow-up, 14,066 people died of lung cancer. RESULTS: In analyses restricted to lifelong nonsmokers who did not report preexisting disease, leanness was not substantially associated with lung cancer mortality in men (rate ratio = 0.9; 95% confidence interval = 0.3-3.1) or in women (rate ratio = 1.2; 95% confidence interval = 0.7-2.1). However, leanness was associated with increased lung cancer risk in analyses that attempted to control for, rather than exclude, smokers and persons with preexisting disease. CONCLUSIONS: These data suggest that the association between leanness and lung cancer mortality is not causal but rather is an artifact of the effects of smoking and preexisting disease.     

Smoking and deprivation: are there neighbourhood effects?

Debate has centred on whether the character of places plays an independent role in shaping individual smoking behaviour. At the small-area scale, particular attention has focused on whether measures of neighbourhood deprivation predict an individual's smoking status independent of their own personal characteristics. This study applies multilevel modelling techniques to data from the British Health and Lifestyle Survey and ward (local neighbourhood) level deprivation scores based on four variables from the national Census. Results suggest that after taking account of a large range of individual characteristics, both as main effects and interactions, together with complex structures of between-individual variation, measures of neighbourhood deprivation continue to have an independent effect on individual smoking status. In addition, significant between-ward differences in smoking behaviour remain which cannot be explained either by population composition or ward-level deprivation. The study suggests that the character of the local neighbourhood plays a role in shaping smoking behaviour.     

Indoor allergen exposure in west and East Germany: a cause for different prevalences of asthma and atopy?

West and East Germans have been living in two different political systems for 40 years. These two populations have become a classic epidemiological example for the hypothesis that lifestyle changes accompanying the industrial and economic development of modern societies are responsible for an increase in the prevalence of atopic diseases. A higher prevalence of atopic sensitization, asthma, and hay fever was found in young West Germans after the unification. It has been hypothesized that this phenomenon was at least partially due to the installation of insulating windows and central heating systems in Western homes, favoring the growth of microorganisms like mites and moulds and increasing indoor allergen exposure. This review summarizes studies that have investigated reservoir concentrations of indoor allergens in public buildings and private homes in East and West Germany. Whereas a higher prevalence of atopic sensitization in West Germans was found for nearly all tested allergens (cat, mite, pollen), allergen exposure was higher only for cat allergens, but probably not for mite and cockroach allergens or moulds. The published data do not support the view that the differences in specific sensitization are caused by differences in the exposure to specific allergens.     

Substance abuse and homelessness: direct or indirect effects?

PURPOSE: To investigate whether substance abuse is a direct factor in the explanation of homelessness or one that operates indirectly through disaffiliation and human capital processes to place individuals at greater risk of the condition. METHODS: Analyses were conducted using data on substance abuse and homeless experiences from a random probability sample of 481 homeless persons and those at risk of homelessness in Cook County, Illinois. Covariance structure models were used to assess substance abuse, human capital, and disaffiliation as potential precursors of homelessness, with particular attention paid to the direct and indirect role of substance abuse in the loss of domicile. RESULTS: Analysis of several nested models of homelessness links substance abuse only indirectly to loss of domicile, primarily through its impact on social and institutional affiliations. Contrary to expectations, substance abuse did not impact homelessness indirectly by diminishing the accumulation of human capital. CONCLUSIONS: The role of disaffiliation as a proximate cause of homelessness was confirmed. This locates the phenomenon within the context of society itself, as a direct result of a breakdown in the social bonds necessary for human community. Substance abuse plays a critical role in this breakdown, negatively influencing social as well as institutional relationships.     

Invasive pneumococcal and meningococcal disease: association with influenza virus and respiratory syncytial virus activity?

Few studies have examined the relationship between viral activity and bacterial invasive disease, considering both influenza virus and respiratory syncytial virus (RSV). This study aimed to assess the potential relationship between invasive pneumococcal disease (IPD), meningococcal disease (MD), and influenza virus and RSV activity in The Netherlands. Correlations were determined between population-based data on IPD and MD during 1997-2003 and influenza virus and RSV surveillance data. Incidence rate ratios of disease during periods of high influenza virus and RSV activity over the peri-seasonal and summer baseline periods were calculated. The analyses comprised 7266 and 3072 cases of IPD and MD. When data from all seasons were included, the occurrence of pneumococcal bacteraemia and MD correlated significantly with influenza virus and RSV activity both in children and adults. Periods of increased influenza virus and RSV activity showed higher rates of pneumococcal bacteraemia in older children and adults than the peri-season period. Rates of MD in children were also higher during periods of increased influenza virus activity; the same appeared true for MD in older children during periods of increased RSV activity. Although no causal relationship may be inferred from these data, they support a role for influenza virus and RSV in the pathogenesis of IPD and MD.     

What was the first epidemiological study of smoking and lung cancer?

Based on his critique of the early case-control study of smoking and lung cancer by Mueller, Morabia questions the priority that has been assigned to this research. I examine Morabia's approach to retrospectively assess quality and question its general applicability and replicability. By citation analyses, the case-control studies published in the 1950s have had far greater impact. Morabia's commentary points to the complexity and subtlety of re-interpreting older literature.