National Workshop on Asthma and the Environment

A national workshop on asthma and the environment was 
held October 23 and 24, 1992. in Montreal, Quebec. 
Twenty-nine speakers presented data on asthma from a 
Canadian perspective. A nun1hcr of recommendations were 
produced which will influence future asthma research and 
management in Canada.


Atelier national sur l'asthme et I' environnement
Un atelier national sur l'asthmc et l'environnemcnt s'est deroule du 23 au 24 octobrc a Montreal (Quebec).Vingtn...:uf conferenc iers ont presente des donnees d'un point de vue ca nad ien.Un certain nombrc de recommandations formulees a cette occasion orienteront Ia recherche future et le lrai tement en matiere d' asthme au Canada.area of the hotel.Almost all of the participants were Canadi an, but Ann Woolcock of Australia, who was in the country as Sim ms Travelling Profe ssor of the Royal College of Physicians.was invited to attend.
Sessions were co-chaired by MargareL Beck lake from Mon treal, and Moira C han-Yeung from Vancouver.Or Cha n-Yeung stated the workshop's aims: • to ident ify and catalogue ongoing Canadian research on asthma and iLs relation to the environment; • to propose and improve study designs as well as standard ize health and environmental measures to promote comparability of results across Canada and ;1void duplication of efforts; and • to recommend an agenda for research and action for reduc ing asth ma morbidity in Canada in the nex t fiVl' years.

ASTHMA:BACKGROUND
Dr Chan-Yeung descri bed asthma as a multifactorial disease.She felt the most important determinants arc genetic predisposition and exposures in the environment.both indoor and outdoor.She introduced the concept of 'inducers' of asthma and 'triggers• or asthmatic allacks.Inducers are agents that may cause asthma in a previously healthy subject.fnduction of asthma is associated with an increase in bronchial hyperresponsiveness, and occurs with allergens such as house dust mites, pollens, fungi and industri al exposures such as isocyanates.T riggers of asthma are agents that provoke attacks of asthma in a known asthmatic, and usually not associateJ with an increase in bronchial hypenesponsivcness.Stimuli that can trigger attacks include exerc ise, cold air and exposure to air pollutants.
Dr Chan-Yeung stated that genetic predisposition also plays an importa nt part in asthma; little is known ahout genetic markers.and there is more understanding of the genetic aspects of atopy.Sensiti zation to common allerge ns occurs in the first two years of life, and studies of the interaction between atopic predisposition and envi ronmental exposure during this window of life are likely to add to our understanding of asthma.
Svene Veda! , also from Vancouver, reviewed asthma and air pollution episodes.Outbreaks or as thma in Barcelona, Spain, were recently shown to he due to airborne soybean dus t from the unloading ofsoyhean in the city harbour.Other outbreaks, although not as clearly attributed to organic dusts, have been Jcscrihed in New Orleans, Louisiana, in Mi nneapoli s, Minnesota.and in Yokohama, Japan.
In the past, severe air pollution episodes have heen accompanied by dramatic increases in respiratory illness and death .with most deaths occurring in people with chronic obstructive lung disease.The best known cpisoJc occuned during the smog of 1952 in London, England.
Exposure to ae roallcrgens such as pollen and pet allerge ns can clearly cause exacerbations in asthmatics, but it is less clearly appreciated that exposure to house dust mites and fun gal spores can also lead to exacerbations.
Most of the information on the adverse health effects of air pollution involve suspcnJcJ particles.su lphur dioxide, nitrogen dioxide or 01.onc.Ambient su lphur dioxide is largely produced by the combustion of foss il fue ls that contai n su lphur impurities ; ground level ozone is formed by the interaction of nitrogen oxide (large ly produced by automohiles), hydrocarbons and su nlight.The combination of ozone with other contaminants may be mon: harmful than exposure to ozone alone.The concentrations of sulphur d ioxide and ozone are generall y low indoors.with the exception of homes with kerosene heaters where high sulphur Ji ox idc conce ntrations have been measured.Indoor nitrogen dioxide from the combustion of natural gas in gas stoves appears to cau e more respiratory symptoms in children.but has not been shown to affect asthmatics more adversely.

ASTHMA AND THE INDOOR ENVIRONMENT
Dr Woolcock presented data on the relation of house d ust mites and asthma, a theme which surfaced repeatedly at the workshop.In a study of 807 children aged eight to 11 years in a humid rural area of Australia, where house dust mite allergen levels were so high they set records, 27% of the children wheezed.19% had airway hypcncactivity and I( %; had hoth, meeti ng Dr Woolcock• s criteria for current asthma .
In another, less humid.area the prevalence of asthma in chilJrcn was 8.7 1 k.Risk factors for asthma were allergy.parental asthma and a respiratory illness under the age of two years; sex, age, and parental smoking were not important risks, once these factors had been accounted for.Among atopic children, allergy to house dust mites was the greatest risk factor, fo llowed by allergy to cats and Alternariu spores.
Claire Infante-Rivard of Montreal studied the indoor environment and asthma in three-and four-year-old children who presented to emergency rooms.The pred ictors or asthma were familial susceptibility, the mother's (or babysitter's) heavy smoking, a hu midifier in the child's room, and an electric heating system in the house.Twenty per cent of the children were asked to wear a nitrogen dioxide badge for 24 h, and there was a dose-re ponsc relationship between asthma and nitrogen dioxide levels; in houses built after 1970 thi s ri sk increased.
rn a second Montreal study of six-to 12-year-olJ school children by Pierre Ernst, however.lhere was no strong association hctwcrn asthma anJ crowding, da mp damage, cooking fuels or env ironmental tobacco smoke.And in a third study done in Pmt Alberni, British Columbi a, hy Svcrrc Veda), peak expiratory flow rate (PEFR) variability was increased in children with high house dust mite exposure, but asthma was not assoc iated with a cat in the home.
Alexander Ferguson, Vancouver, recommended controlling house dust mites by covering mattresses with zippered plastic covers, removing carpets, washing beddi ng in water at 55°C, and lowering the indoor humidity to 50%.Several acarac ides arc e ffective bu t they require freq uent application and although they kill mites, they do not remove the allergenic protei ns.Vacuum cleani ng and carpet shampooing arc ineffecti ve, and increas ing ve ntilation in the home works only if outside hu midi ty is low .
Paul Comptoi s of Montrea l repo rted that indoo r factors intluencing asthma include natural materials in the bedroom (especially cotton mattresses).wood walls and floors.and molds.ch ietly A.1pergil/11s anJ Pe11ici/li11111 spores.The smaller a spore is, the more li kely it is to become airborne anJ affect health.Plants do not have an impact, nor docs humidity unless it is related to a home nebulizer.
The study of allergy and ex posure to molds has lagged behind that of house dust mite exposure, according to Zave Chad, Montreal.Dr Chad called molds " the forgotten aeroallergens in asthma", a nd felt thi s was because they are so hard to quanti fy.C/adospori11111, Alternaria.Pc11icilliu111 and Aspergillus are the most commonly fo und spores.and the last two arc the most com mon indoors.Fungal volatiles are frequently detected as moldy smells.but there arc no data available on their long term effects.
Asthma and nonallergic exposure in indoor air was Jiscussed by Denn is Bowie from Halifax, Nova Scotia.A number or combustion products, volatile organic products.bioaerosols, particulates and iITitant gases are found in indoor air.Thei r concentrations are altered by temperature, humidity, ventilation, and the use of a ventilating system (but not filters); the effect of combined exposures is not known, although these agents are incriminated in 'sick building syndrome'.An aura of hysteria surrounds the subject and objecti ve ev idence of obstructive airway disease is hard to find.
Richard Menzies surveyed by questionnaire the role uf aeroallergens in producing respiratory symptoms in full-time workers in six office buildings in Montreal.Although over half the workers who had symptoms said they improved when they stayed away from work.there was no significant difference between cases and controls in environmental conditions and the level of aeroallcrgens.As in similar studies, the office environment was measured on only a few occasions and significant exposures could have been missed .

ASTHMA AN D THE OUTDOOR ENVIRONMENT
Several speakers discussed the relation of community air pollution and asthma admissions .Analysis of data obtained in Ontario between 1983 and l 988 by Richard Burnett.Ottawa, showed a peak of asthma admissions in September.with acute bronch itis, pneumonia and chronic respiratory disease peaking in January in relation to the annual influenza epidemic .Respiratory admission rates from May to August correlated with sulphur dioxide levels measured on the day of admission and up to three days before.Burnett found a similar pattern with ozone.except that there is little effect on the day of admission, and ozone and sulphur dioxide seem to have a synergistic effect.
In Mon treal.Ralph Delfino found admissions from 1983 to 1988 to 31 hos pi tals for all respiratory illnesses, with and without asthma, were significantly associated with level s of sulphate, particks less than l O µm in size.and total suspended particles, des pite the fact that levels of these materials rarely exceeded Canadian standards.
A study of asthma at the Winnipeg Children' s Hospital in 1991, by Jure Manfreda, did not show correlations between tree and grass pollens.emergency room visits and asthma admissions, but ragweed counts did corrclak with emergency room visits and less well with admissions.Other Man itoba data collected between l 979 and 1989 showed no association between asthma and sulphur dioxide, nitrogen dioxide or ozone, but there was a significant relationship between asthma and total suspended particles.
In the Ottawa-Carleton region a fall peak in asthma adm issinns follo ws the peak of the ragweed and mold seasons by a few weeks .Th is suggests that these allergens may induce late-phase intlamatory responses and increase bronchial reactivity to set the stage for vimses, pollutants or othe r allerge ns to act.These data were reported by Michel Droui n.Ottawa.
T he relation of asthma and the outdoor environment is still Car from clear.The use of general practitioners' and specialists' services by asthmatics, reported by David Pengelly , Hamilton, was associated with increased sulphur dioxide levels and coefficient of haze (a measure of fi ne particle concentration), although not with increases in ozone or other pollutants.
In an exhaustive examination of environmental and hospital data from Saint John, New Brunswick, by Robert Can Respir J Vol 1 No 1 Spring 1994

Asthma workshop
Beveridge, no relationship between environ mental pollution and emergency visits for asthma was found, although there was a weak corre lation between nitroge n dioxide and ozone and respiratory symptoms of cough, congestion, d ifficulty breathing, and shortness of breath .Dr Beveridge presented the workshop's most dramatic image, that of a cloud of ozone moving up the eastern seaboard of the United States, arriving at the Maine-New Brunswick border at midnight, and reaching the St John River Valley at about 02 :30.
Pierre Lajoie, Quebec City, reported a significant negative association between the number of emergency room visits per day and temperature, and weak associations between visits and ozone and nitrogen di ox ide levels.Dr Laj oie mentioned the impressive facts that 12% of 3005 asthmatics visited the emergency room three or more times.accounting for 36% of the visits, and that al most 25 % took no drugs, even though they repeatedly visited the emergency room.
All an Becke r, W innipeg, investigated both outdoor and indoor allergens on the prairies, and found that tree and grass pollens did not conelate with emergency room visits or hospital admissions.but ragwei.:dcorrel ated strongly with visits.and significantly with admissions.No correlation was found between visits and total mold counts, and although the seven-day cumulative valUL' ror Alternuriu correlated with emergency room visits, there was no admission s peak.Using a multiple regress ion analysis.both emerge ncy room visits and admissions showed a strong association with ragweed and Cladosporum spores in the late summer and early fa ll.
Susan Tarlo, Toronto, reported on the factors associated with low level ozone and airway disease.The most important is the dose of ozone delivered to the ai rways, which depends on the ambient concentration, the expired mi11ute volume (FEY 1 ), and the duration of exposure.The current Canadi an ambient air quality standard fo r ozone is 0.08 parts per million (ppm) for I h, but levels in some Canadian cities during the summer reach 0.1 6 ppm or more .
The interaction of ozone and aeroallergens was investigated by Noe Zamel , Toronto.He fo und no significa11t differences in FEY I after exposure to ozone but whe n allergen was prccceded by ozone, there was an increase in bronchial reactivity .
The last speake r of the session on the outdoor envi ronment was Ambikaipakan Senthiselvan, Saskatoon.In hi s investigations of pesticide-induced asthma in male Saskatchewan farmers, he found a significant association betwec11 asthma and exposure to cholinesterase-inhibiting insecticides.

ASTHMA IN CANADA TODAY
A problem for those who teach or speak in public is that simple, tip-to-date numbers that the public can easily u11derstand are difficult to obtain .Kathryn Wilkins, an epidemiologist with Health Canada's Laboratory Centre for Disease Control who edits Chronic Diseases in Canada.reported a number of useful fig ures.An average of 11 children under 15 years of age die in Canada of asthma every year.Although from age 15 to 34 the death rate is twice that of the younger age group, the death rate has not changed since the 1980s.
However, hospitalizations for asthma increased by 40% between 1980 and 1988.and the rate of admission was five times higher for people under 15 years than for those aged 15 to 34.The rate of first-ever medical consultations for asthma doubled between 1979 and 1990, suggesting that the incidence of the disease in Canada has increased.
Robert Dales, also from Ottawa, reviewed the prevalence of asthma in Canada.Using a questionnaire, he surveyed 17,962 families of children five to eight years old and found that 4. 7% had physician-diagnosed asthma.13% had wheezing and 69' o had persistent cough.Asthma prevalence was highest in the Maritimes (7 .4%)and lowest in British Colombia (3.3 %) and Quebec (3.4%).This regional variation corresponded to distances between provincial hospitals, and was not explained by child's age and sex, respondent's age, passive smoking.gas or wood stoves, home mold/dampness, maximal parental education.pets, or hobbies in the home.
Lamont Sweet.Charlottetown, discussed a study which was done on asthma deaths in Prince Edward Island because, except for the year I 980, asthma deaths in that province from 1979 to 1988 appeared to be three times the national average.There were 34 coded asthma deaths in the years 1984 to 1988, and their death certificates, hospital charts and autopsy reports were reviewed.Using established criteria for asthma death, only three cases under l'ive years and four cases over 49 years were considered valid diagnoses of asthma.A total of 22 cases (6Yl<l) were judged to be invalid, all over 50 years of age; the records had been coded incorrectly due to physician misunderstanding.or to an international coding rule which gave precedence to asthma deaths over other causes appearing on the death certificate.Dr Sweet also reviewed Prince Edward Island's asthma hospitalization study, in which a 10% sample of 4230 hospital charts were reviewed; the valid admission rate was found to be 69°/o .Patients from rural areas were under-represented, and the diagnosis of asthma was found to be most accurate (88% ) in the 10-to 39-year-old age group.

NEW TECHNIQUES FOR THE INVESTIGATION OF ASTHMA
Irving Broder.Toronto.discussed the investigation of air pollution, commenting that after 1975 research used detailed examination of exposures in susceptible populations, with searches for dose/response relationships.Since a biological dose is rarely available, data from government measurements at fixed outdoor sites can be used, despite the fact that they are imprecise and do not represent what happens indoors.Exposure models are currently being developed, which will provide the most precise estimate while exposing the subject to the least risk, and at a low cost.
Frances Silverman.Toronto, described three approaches to research on asthma.Animal studies provide evidence of pollution-induced damage, but it is difficult to extrapolate the results to humans, and experiments are ofte n done at higher levels than humans encounter.Epidemiological studies allow examination of complex outcomes, but because of the complexity of air pollution mixtures it is difficult to establish cause/effect and dose/response relationships.The third technique is the 'clinical study'. in which human subjects are exposed to low levels of pollutants under controlled laboratory conditions.Dr Silverman echoed Dr Broder's contention that experimental human e xposure in the laboratory allows for control of variables, but the number of subjects is limited.it is difficult to duplicate environmental conditions, and ethical considerations impose constraints.Accidents with high concentrations (such as Bhopal) can also be examined, allowing the study of conditions which cannot be used experimentally for ethical reasons.
New techniques which could be used in asthma investigation in Canada were discussed.Mark Raizcnne, Ottawa.described a 'spiromodem', an instrument which will allow subjects to record spirometry independently at home and down load it to a computer at another location at an appropriate time.
Anuther research tool for population studies is PEFR variability, discussed by Robe1t Cowie, Calgary.Dr Cowie stated that questionnaire responses are not specific for asthma and they may be insensitive because they depend on community awareness.He felt that the PEFR, although it might not detect all the asthmatics in a population, could easily give an index of prevalence.
Finally, James Day of Kingston described an environmental chamber that he and R Clark developed which exposes individuals to environmental materials and allergens in a controlled fashion and allows the careful evaluation of resulting respiratory tract disease.

PROPOSED RESEARCH
Pl ans for four research projects were described and discussed.The first, by Suzanne Tough, Edmonton, will study all patients aged five to 50 years dying of asth ma in the prairie provinces from November I, 1992 until No vember I. 1995.
Information about the patients' demographics, lifestyle, medication , occupation and their acute event will be sought.Thi s will be compared with data from population controls matched for age, gender, demographic variables and characteristics of disease.A second control group will consist of matched cases of asthma treated in an emergency within two weeks of the fata l case.It is anticipated that 70 fatal cases of asthma will be collected, and lead to a clearer understanding of the factors involved in high ri sk cases.
The Laboratory Centre for Disease Control.Health Canada, will participate in the prairie provinces project, according to Dr Felix Li, Ottawa, and will also incorporate an asthma questionnaire into the 1994 and subsequent Canada Health Surveys.
Patrick Hessel, Edmonton, described plans for a third study which will investigate conditions in four commun ities in Alberta where citizens have expressed concerns about the effects of pollution from local petrochemical or forest produc t industries on their lung health .
A fourth project was described by Donald F Stark, Vancouver.The Canadian Society of Allergy and Clinical Immunology plans to estimate the prevalence of atopic disease with a study of 2000 Canadian students aged 17 to 25 years who have lived for three or more ye:u-s in the same place.

RECOMMENDATIONS OF THE WORKSHOP
After a great deal of discussion, 30 recommendations were made.The fi rst of these, as might be expected from a meeting where the value of communication was so amply demonstrated, was that more workshops should be held.having a similar format, to discuss study design, maximize resource use, and avoid duplication of effort.The rest of the rernmmendations, although they covered many specific issues which the participants felt should be specifically mentioned, could be collected into four main themes.
The first was the importance of establishing standardized instrnments for the collection of data, with recommendations regarding the use of a standardized asthma questionnaire, standardized skin testing methods.and the use of sentinel Can Respir J Vol 1 No 1 Spring 1994 Asthma workshop hospitals and physicians to provide quality data in an organized and consistent way.
The extent and the depth of the discussion made it clear to all participants that much more needs to be known ahout asthma, both in terms of aeroallergens and the environment in and out of doors.This leads to another group ol' recommendations, for the establishment of nationwide aeroallergen and air pollution monitoring networks, and for the inwstigation of the interaction of the many factors involved.
Another common theme in the recommendations was that methods for the control of factors causing asthma need to be sought.This could begin with the setting of reasonable air pollution standards.
The final group of recommendations concerned the dissemination of information 011 the management of the two causes of asthma about which much is already known: the abolition of cigarette smoking, and the control of the house dust mite.