Epidemic of asthma possibly associated with electrical storms

Abstract

possibility of bias but also the plausible direction in which it might operate.We were at great pains, even in the title of our paper, to show that our findings supported a familial aetiology and that this might be genetic. On the other hand, the segregation analysis makes the genetic aetiology more plausible; we made it quite clear that this was not proof. We also pointed out that voluntary childlessness might not have been exactly the same in both groups, and therefore we performed a sensitivity analysis to see what effects this bias might have had on our conclusions -a point that Gregson and colleagues overlook.The high incidence of subfertility would not seem to explain the striking similarity in the sperm counts across the three families in which extended sampling was permitted.Our paper shows that we were aware of all the biases identified by Gregson and colleagues, and more besides. We believe that our findings should be corroborated and that they are an intriguing clue. If Gregson and colleagues can suggest a method to overcome bias arising from what must inevitably be verbal evidence then we would love to discuss it with them. We would, for example, like to know whether they really think that observers could be blinded in a study of genetic histories and whether this has been accomplished successfully for other topics for which genetic histories are required from cases and controls.With regard to the letter from F J Stewart and A J Hill, absence of the vas deferens causes azoospermia, whereas we were concerned with oligozoospermia. There is no particular reason for thinking that oligozoospermia might be associated with mutations in the cystic fibrosis gene.

A major outbreak of asthma associated with a thunderstorm: experience of accident and emergency departments and patients' characteristics

“…The outbreak was not restricted to the London area,5 6 7 although the number of patients presenting to accident and emergency departments on the night of 24 June 1994 was greater in the Thames regions than in other regions in England 7. Furthermore, not all affected patients attended hospital 8.…”

Thunderstorm associated asthma: a detailed analysis of environmental factors

“…Thunderstorms in which fungal spores and rye grass pollen were implicated as the precipitating factors in asthma epidemics occurred in Birmingham in 19838 9 and Melbourne in 1984 10 11 12. Campbell-Hewson et al reported that the asthma epidemic in Peterborough and Cambridge in June 1994 was associated with a thunderstorm in which there were high ozone concentrations, high pollen counts, and high fungal spore counts with varying levels of atmospheric electrical activity 2. Our findings in west central London suggest that a fall in air temperature and a high pollen count were the best predictors of the asthma epidemic, though all the individual environmental variables were closely related.…”

“…On 24 and 25 June 1994 an acute outbreak of asthma occurred in southern England associated with a thunderstorm 1 2. The abrupt rise in the number of patients presenting with asthma to the accident and emergency department of St Mary's Hospital in west central London provided an opportunity to assess whether there had been any precipitating environmental factors.…”

Reporting of air pollution levels

“…EDITOR,—Two articles in the issue of 22 October reported levels of air pollutants and their possible health effects 1 2. Gregor Campbell-Hewson and colleagues refer to ozone levels being “at a two week high” and report a figure of “45 ppb, compared with a daily average of 28.7 ppb over the preceding and following weeks.”1 Was this value an hourly maximum value for that day, the eight hour mean (for which the Expert Panel on Air Quality Standards has recently set a new standard of 50 ppb3), or a 24 hour mean?…”

“…Gregor Campbell-Hewson and colleagues refer to ozone levels being “at a two week high” and report a figure of “45 ppb, compared with a daily average of 28.7 ppb over the preceding and following weeks.”1 Was this value an hourly maximum value for that day, the eight hour mean (for which the Expert Panel on Air Quality Standards has recently set a new standard of 50 ppb3), or a 24 hour mean? On how many days over the preceding and following weeks (I presume one week each side) was an equivalent value recorded?…”