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Allergies and asthma
In dealing with allergies and asthma, Lomborg stresses all factors that relate to our own choice of life-styles, such as tobacco smoking and increased insulation of our homes. On the other hand, he downplays the importance of all factors that relate to the non-chosen environment, such as air pollution. At the time when his book was written, this weighting of life-style versus pollution was biased relative to the existing evidence. Since 2001, more evidence has appeared that air pollution may exacerbate and even cause asthma, and therefore the text now (2005) appears more biased than it did in 2001.
Much useful information on the subject may be found in the following review paper, which potentially was available to Lomborg: P. A. Eggleston et al. (1999): The environment and asthma in U.S. inner cities. Env. health perspect. suppl. vol. 107, no. S3, pp. 439-450. A paper which directly criticises Lomborg´s treatment of the subject is A. Bodnar et al. (2004): Lessons learned from "The Skeptical Environmentalist": an environmental health perspective. Int. J. Hyg. Environ. Health 207: 57-67.
P. 186 left: (SLIGHT BIAS)
"A recent meta-study . . . in the British Medical Journal concluded that . . " Comment: It is true that the conclusion of that paper contains the quoted sentence, but Lomborg has omitted the first part of the sentence, which reads: "Until such studies have been performed on more than one occasion in the same population we believe that . . etc." The meta-study included 16 original studies, all of which fulfilled certain strict conditions, including that the same methodology was used at start and end of the study period. The authors concluded that all studies showed increasing prevalences of asthma, and that selection bias is unlikely to explain the observed trends. Note that another meta-study, presented in Lomborg´s figure 101, indicates the same.
P. 186 bottom left: (SLIGHT BIAS)
"A slight increase in mortality over the past 20 years . . ". Comment: The reference NHLBI and WHO 1995 is no longer available. Lomborg´s text follows rather closely the other reference, Jarvis & Burney 1998, but with some slight changes in what is stressed. The original paper states the following: "More recent increases in asthma mortality reported from Britain, France, and the United States may be related to increased prevalence or severity of asthma or inadequate health care." Thus, according to this source, the increase is not "slight" (a figure presented in the paper demonstrates nearly a doubling from 1976 to 1986). The original has the wording "may be related to" which by Lomborg has been changed into "is assumed primarily to have been caused by".
P. 186 bottom right: (COMMENT)
"There generally seems to be more [asthma] in towns and cities than in the countryside." Comment: A review paper by Eggleston et al. (1999) is titled "The environment and asthma in U.S. inner cities". This was potentially available to Lomborg. If he had studied this paper, or the literature cited in it, he would have avoided a number of errors in the following text.
P. 186 - 187: ERROR
"It turns out that although pollution can make things worse for asthma sufferers, it cannot in itself cause the disease." Error: As reported by Eggleston et al. (1999) (see above), when non-allergic humans or experimental animals are exposed to diesel exhaust particles, this leads to allergic reactions, such as airway inflammation. The authors write: "Taken together, these studies suggest that exposure to ambient particulates may play a role not only in exacerbation of existing allergic disease, but may also contribute to the recent rise in the prevalence of asthma." A more recent paper (J. Grigg (2002) Arch. Dis. Child 86: 79-83) argues that the smallest fraction of of particles in air pollution have actually been increasing in the industrialised countries over the last decades, and may be an important causal risk factor for allergic disease.
P. 187 top left: (COMMENT)
"In fact, the official British committee . . . drew the somewhat surprising conclusion . . ". Comment: Lomborg refers to a report from 1995. This is now outdated. Already before 2001, when his book was published, evidence had been obtained that contradicted the conclusions (see Eggleston et al. 1999), and even more evidence for the impact of physico-chemical air pollution on children with asthma has been added in recent years (see e.g. Committee on Environmental Health (2004): Pediatrics 114: 1699-1707).
P. 187 left: ERROR
"The only obvious external air pollution causes are biological pollutants. . . " Error: In 2001, when TSE was published, there existed evidence for the impact of non-biological air pollution on children with asthma, and more evidence has been added since then. Eggleston et al. (1999) refer to a California study that 76 % of all particles in indoor air was from outdoor sources, and to other studies indicating that outdoor sources contribute to the elevation of NO2 in indoor air. Air pollutants that exacerbate asthma include particles, NO2, and ozone. The possible effects of ozone were mentioned already by Eggleston et al. (1999), and they have been confirmed by more recent research. See J.F. Gent et al. (2003): J. Amer. medical ass. 290: 1859-1867; R. McConnell et al. (2002): Lancet 359: 386-391. Review articles include e.g. J. Sunyer (2004): Eur. Respir. J. 23: 185-186.
P. 187 left: FLAW
"By far the majority of asthmatic patients are also hypersensitive to dust mites . . ". Flaw: This is not true for people in large cities, and Lomborg has just written (p. 186) that there is more asthma in cities than in the countryside. The percentage of the asthmatic children who live in large cities in USA that were allergic to various allergens was as follows (Eggleston et al. 1999): Alternaria spores (38 %), cockroaches (36%), house dust mites (35%), cats (24%), rats (19%), dogs (16%) and mice (15%). The same data are presented in Rosentreich et al. (1997), which Lomborg has read. Lomborg´s words, "by far the majority", seem to overstate the role of mites.
P. 187 right - 188: (COMMENT)
Lomborg presents the "hygiene hypothesis" and concludes that development of asthma is due to changes in our life-style, rather than due to environmental factors. Comment: Although the "hygiene hypothesis" seems to be corroborated by recent research, it would be wrong to state that the indoor environment is solely a question of life-style. A British study has shown that asthma among children is more prevalent in families where the home is kept clean. More specifically, there was a correlation between the use of household chemicals and asthma, and this finding was independnet of numerous potential confounding factors. It seemed that there was an effect of the use of household chemicals per se, during and after the mother´s pregnancy. See A. Sherriff et al., Arch. Dis. Childhood 87 (2002): 30-35 and Thorax 60(2005): 45-49.