Showing papers by "Neil Pearce published in 2003"

Bioaerosol Health Effects and Exposure Assessment: Progress and Prospects

Abstract: Exposures to bioaerosols in the occupational environment are associated with a wide range of health effects with major public health impact, including infectious diseases, acute toxic effects, allergies and cancer. Respiratory symptoms and lung function impairment are the most widely studied and probably among the most important bioaerosol-associated health effects. In addition to these adverse health effects some protective effects of microbial exposure on atopy and atopic conditions has also been suggested. New industrial activities have emerged in recent years in which exposures to bioaerosols can be abundant, e.g. the waste recycling and composting industry, biotechnology industries producing highly purified enzymes and the detergent and food industries that make use of these enzymes. Dose-response relationships have not been established for most biological agents and knowledge about threshold values is sparse. Exposure limits are available for some contaminants, e.g. wood dust, subtilisins (bacterial enzymes) and flour dust. Exposure limits for bacterial endotoxin have been proposed. Risk assessment is seriously hampered by the lack of valid quantitative exposure assessment methods. Traditional culture methods to quantify microbial exposures have proven to be of limited use. Non-culture methods and assessment methods for microbial constituents [e.g. allergens, endotoxin, beta(1-->3)-glucans, fungal extracellular polysaccharides] appear more successful; however, experience with these methods is generally limited. Therefore, more research is needed to establish better exposure assessment tools and validate newly developed methods. Other important areas that require further research include: potential protective effects of microbial exposures on atopy and atopic diseases, inter-individual susceptibility for biological exposures, interactions of bioaerosols with non-biological agents and other potential health effects such as skin and neurological conditions and birth effects.

Is Social Capital the Key to Inequalities in Health

Abstract: There has been vigorous debate between the “social capital” and “neomaterialist” interpretations of the epidemiological evidence regarding socioeconomic determinants of health. We argue that levels of income inequality, social capital, and health in a community may all be consequences of more macrolevel social and economic processes that influence health across the life course. We discuss the many reasons for the prominence of social capital theory, and the potential drawbacks to making social capital a major focus of social policy. Intervening in communities to increase their levels of social capital may be ineffective, create resentment, and overload community resources, and to take such an approach may be to “blame the victim” at the community level while ignoring the health effects of macrolevel social and economic policies.

Pollen counts in relation to the prevalence of allergic rhinoconjunctivitis, asthma and atopic eczema in the International Study of Asthma and Allergies in Childhood (ISAAC)

Abstract: Background Although pollens are major allergens associated with allergic rhinoconjunctivitis and asthma, there is little information about the relative prevalence of these conditions in populations with different pollen exposures. Objective The purpose of this study was to investigate the relationship between pollen exposure and allergic symptoms among children in different countries. Methods An ecological analysis was conducted to see whether pollen exposure (pollen counts, and duration and severity of pollen seasons) is associated with symptoms of allergic rhinoconjunctivitis, asthma and atopic eczema in 28 centres within 11 countries (nine being in Europe). Data on the prevalence of symptoms in 13–14-year olds were based on the responses to the written questionnaires from the International Study of Asthma and Allergies in Childhood (ISAAC). The analysis was adjusted for gross national product and mean annual relative humidity. Results There was little relationship between pollen exposure and symptom prevalence, except for a significant inverse association between grass pollen counts and lifetime prevalence of the symptoms of allergic rhinitis (P=0.03). Almost all the regression coefficients were negative. The associations were even weaker and all non-significant when the analyses were conducted within countries, using a random intercept fixed slope model, but there was still no evidence of a positive association between pollen exposure and symptoms. Conclusion There is a weak but consistent tendency for the prevalence of allergic symptoms to be inversely associated with pollen exposure. This finding accords with evidence from several countries, suggesting that the prevalence of hayfever and asthma tends to be lower in rural than in urban areas, and lowest among people living on farms. Exposure to allergenic pollen in early life does not appear to increase the risk of acquiring symptoms of respiratory allergy, and may even give some protection against them.

Invited Commentary: Is Indoor Mold Exposure a Risk Factor for Asthma?

Abstract: A remarkably consistent association between home dampness and respiratory symptoms and asthma has been observed in a large number of studies conducted across many geographic regions (1–10). In a recent review of 61 studies, it was concluded that dampness was a significant risk factor for airway effects such as cough, wheeze, and asthma, with odds ratios ranging from 1.4 to 2.2 (8). Positive associations have been shown in infants (4, 5), children (1, 2, 10), and adults (6, 7, 9), and some evidence for doseresponse relations has also been demonstrated (11). Although it has been concluded that the evidence for a causal association between dampness and respiratory morbidity is strong (3, 8), this evidence is based mainly on crosssectional studies and prevalence case-control studies; few prospective studies have been conducted (12). Therefore, it is not clear whether indoor dampness causes or only exacerbates preexisting respiratory conditions such as asthma. Interestingly, a recent large European multicenter study in adults showed not only a significant homogenous association across centers between self-reported mold exposure and asthma symptoms but also a higher prevalence of asthma in centers with high self-reported indoor mold exposures (9); this suggests that dampness/moldiness may potentially be involved in the primary causation of asthma. It is not clear whether molds are merely markers of dampness or are causally related to the symptoms associated with dampness (12, 13). Assessment of exposure to molds in most studies has invariably been done by questionnaire, and it is unknown to what extent questionnaire reports of mold growth correlate with exposure to relevant mold components. The studies that have included objective measurements of mold exposure have generally involved culturing spores from indoor air (14) or from settled dust (15); only a few of these studies showed a positive association between measured exposure and asthma or asthma-like symptoms (see reviews by Verhoeff and Burge (13) and Garrett et al. (14)). Perhaps more importantly, very few longitudinal studies have been performed that have included exposure measurements. Thus, the study by Belanger et al. in this issue of the Journal (16) is one of the first to address the issue of mold exposure and asthma development in a birth cohort study. Belanger et al. measured a number of indoor exposures early in life, including mold exposure, both by questionnaire and by measuring total airborne culturable spores, and studied the association with wheeze and cough at 12 months of age. Interestingly, the strongest association was found for mold exposure, whether it was assessed by questionnaire (odds ratios = 1.55–2.27; p < 0.05) or by measured exposure (per 20 colonies, odds ratios = 1.10– 1.23; p < 0.05 only in children whose mothers had asthma), whereas no associations or only minor associations were found for indoor allergen levels. Mold effects were most pronounced among infants whose mothers had asthma, which suggests potential differences in susceptibility to these exposures for children with and without asthmatic mothers. In a previous article, Gent et al. (17) showed in the same infants that high levels of measured Penicillium were significantly associated with both wheeze (relative risk = 2.15; p < 0.05) and persistent cough (relative risk = 2.06; p < 0.05). No associations were observed for other mold species. These results thus suggest that early mold exposure may increase the risk of asthma (with perhaps a larger risk for children of asthmatic mothers). However, these findings should be interpreted with caution because of the poor predictability of early wheeze and cough in asthma development (18). In addition, infants were selected on the basis of having an older asthmatic sibling; therefore, it is not clear whether results can be extrapolated to a “normal,” low(er)risk population. Finally, although the associations with reported exposure were “confirmed” by measured mold exposure, it is debatable whether a one-time measurement of airborne culturable mold spores qualifies as a valid measure of chronic exposure (see below).

Respiratory Symptoms and Occupational Exposures in New Zealand Plywood Mill Workers

Abstract: (GM = 0.7 µg/m3, GSD = 1.8) and were significantly (P < 0.05) higher for workers in the composer area of the process. Geometric mean levels of α-pinene, β-pinene and ∆3-carene were 1.0 (GSD = 2.7), 1.5 (GSD = 2.8) and 0.1 (GSD = 1.4), respectively, and α-pinene and β-pinene levels were significantly (P < 0.001) higher for workers in the ‘green end’ of the process, up to and including the veneer dryers. Formaldehyde levels ranged from 0.01 to 0.74 mg/m3 [GM = 0.08 mg/m3 (= 0.06 p.p.m.), GSD = 3.0]. Asthma symptoms were more common in plywood mill workers (20.5%, n = 112) than in the general population [12.8%, n = 415, adjusted OR (95% CI) = 1.5 (0.9–2.8)]. Asthma symptoms were associated with duration of employment and were reported to lessen or disappear during holidays. No clear association with any of the measured exposures was found, with the exception of formaldehyde, where workers with high exposure reported more asthma symptoms (36.4%) than low exposed workers [7.9%, adjusted OR (95% CI) = 4.3 (0.7–27.7)]. Conclusions: Plywood mill workers are exposed to inhalable dust, bacterial endotoxin, abietic acid, terpenes and formaldehyde, and they appear to have an increased risk of developing work-related respiratory symptoms. These symptoms may be due to formaldehyde exposure, although a potential causal role for other exposures cannot be excluded.

Prevention and control of diabetes in Pacific people.

Abstract: Diabetes is a major problem worldwide. Among Pacific people, prevention and control of diabetes lies in counteracting rapid changes in lifestyle and must take account of political and economic factors and social structure Early studies clearly showed that while diabetes was virtually non-existent in populations indigenous to the Pacific maintaining a traditional lifestyle, the reverse was true for the urbanised Pacific populations.1 In recent decades diabetes prevalence has increased rapidly over time in the indigenous people in the Pacific region (Polynesian, Melanesian, Micronesian), both in the Pacific islands and in countries such as New Zealand.2 Epidemiological evidence indicates that prevalence is generally lowest in traditional Pacific environments, and is higher in both urban Pacific and adopted metropolitan environments; in the latter environments, prevalence is markedly higher in Pacific people than in white people. Prevalence has been increasing rapidly in all three environments, and Pacific people experience greater morbidity and more complications than white people with diabetes. Genetic factors alone cannot explain these patterns, which are due to rapid changes in lifestyle and risk factors such as obesity, unhealthy diets, and physical inactivity that have become widespread throughout the region.2 Although the risk factors associated with diabetes are now reasonably well understood, the prevention and control of the condition in the Pacific, and in Pacific people in Western countries, is not straightforward. We here consider the individual level and population level approaches to diabetes prevention and control in Pacific people. Vigorous pharmacological interventions have a clear role in the management of existing diabetes. Nevertheless, in some Pacific countries a large proportion of resources is spent on identifying people with diabetes and on a variety of non-standardised drug treatment regimens. Modification of individual behaviour is undertaken in less than 5% of the population.3 Given the high cost of …

Changing pattern of ill health for indigenous people

Abstract: Control of lifestyle is beyond individuals and depends on social and political factors Industrialising societies are said to have undergone various epidemiological transition stages, in which the transition from stage two to stage three involves a change from receding pandemics to lifestyle diseases.1 The dynamics of this transition, which took thousands of years in Western countries, have been unprecedented and greatly compacted in time in most indigenous populations. Rather than a transition we see the rise of lifestyle non-communicable diseases at a time when the receding pandemics have not yet receded.2 The pattern seems to be similar in indigenous people in their traditional lands, such as the Pacific, and in newly adopted metropolitan centres, such as New Zealand. We consider here the different dynamics of the epidemiological transition in indigenous people and argue that these are linked to socioeconomic transitions beyond their power and their borders. Thus individual lifestyle interventions cannot be naively transferred to indigenous populations. Rather, what is required is appropriate national and international social and political commitment to health protection, …

Cellular telephone use and time trends for brain, head and neck tumours.

Abstract: Aim The objective of this study was to determine whether incidence rates of head and neck malignancies in New Zealand have varied since the introduction of cellular telephones in 1987. In particular, we sought to compare trends in tumour rates in anatomical sites that receive high, medium and low levels of cellular telephone radiation (based on dosimetry data). Methods We investigated whether trends in tumour incidence rates in New Zealand have varied since the introduction of cellular telephones in 1987. The exposure measure used was the proportion of cellular telephone subscribers within the national population, calculated using the number of subscribers over the study period. Results The graphs for high, medium and low exposure sites did not display any significant changes in trend patterns for either gender over the years 1986 to 1998. Conclusions Incidence rates for malignancies arising in the head and neck, including those sites that hypothetically receive the highest levels of radio frequency radiation during cellular telephone use, have not changed materially since the introduction of cellular telephones to New Zealand. However, ecological studies of this nature are limited in many ways and a stronger study design is clearly needed to establish more exactly any elevation in risk.

Prevalence and causes of diabetes in Pacific people.

Abstract: Diabetes is approaching epidemic proportions among Pacific people both in their traditional homelands as well as in metropolitan centres of their newly adopted Western countries. Although the risk factors associated with diabetes among individuals are reasonably well understood, the "upstream" causes needs to be critically appraised. While individual interventions and health education has its role, there is an urgent need to intervene at the upstream causes of diabetes and other ill health including social, trade, economic and political at the population, state and international level. Attempts to control diabetes in a vacuum without reference to socioeconomic and political context is a convenient vehicle that has contributed to and will continue to fuel calories to the diabetes epidemic.

Epidemiology: populations, methods and theories.

Abstract: There is much that I disagree with in Miettinen's paper [1], including his focus on medicine rather than health, the related view that all epidemiologists should first train in clinical medicine, and his tortous terminology which often involves inventing new complicated terms for old simple concepts. However, these disagreements partly just reflect the fact that Miettinen sees epidemiology through the viewpoint of medicine, whereas I see it through the viewpoint of public health [2]. Bearing these complementary perspectives in mind, there are some key ideas that I agree with, and which I will focus on here.