Q;/Vfed1996; 89:279-284 The increase in hay fever: pllen, particulate matter and SO 2 in ambient air A. SEATON, A. SOUTAR and J. MULLINS 1 Frm the Department f Envirnmental and Occupatinal Medicine, University f Aberdeen, and ^Asthma and Allergy Unit, Sully Hspital, Sully, UK Received 15 September 1995 and in revised frm 22 Nvember 1995 Summary T investigate whether the rise in allergic disease is explicable n the basis f an increase in the cncentratins f allergen and urban air pllutants t which the ppulatin has been expsed, we cmpared the cncentratins f grass pllen, sulphur dixide and black smke t which tw samples f children with previusly measured prevalences f hay fever had been expsed, in Cardiff, Suth Glamrgan. In these studies there had been a 59% increase in the prevalence f hay fever amng 12 year ld schl children between 1973 and 1988. Expsures t grass pllen Intrductin There has been a well-demnstrated rise in the prevalence f asthma and ther allergic diseases in Britain and ther westernized cuntries ver the last 25 years. 1 ' 2 The explanatin fr this is unclear, but is likely t be fund in sme envirnmental change. Tw pssible explanatins have gained sme currency; increased expsure t allergens in the hme and increases in expsure t indr r utdr air pllutin. 3 ' 4 In particular, it has been suggested that the new-brn child is nw expsed t higher cncentratins f mites in huse dust than was frmerly the case, and that this explains the increase in asthma and skin sensitizatin. Hwever, direct evidence that mites have increased is lacking in Britain, the ne lngitudinal study having shwn n such rise ver a 10-year perid. 5 It has been nted that very high mite cncentratins were fund in huses f all scial classes in the 1970s. 6 ' 7 As the prevalence f asthma has risen, s has that f the tw ppulatins had been n different, but the earlier sample, with the lwer prevalence f hay fever, had been expsed t substantially higher cncentratins f ambient particulate matter and sulphur dixide. The rise in prevalence f hay fever, ccurring withut a rise in grass pllen cncentratins, supprts the hypthesis that the ppulatin has becme mre susceptible t airbrne allergen. This increased susceptibility is unlikely t be a cnsequence f cncmitant expsure t sulphur dixide and particulate air pllutin. f hay fever. In Aberdeen the prevalence f the latter was 3.2% in primary schl children in 1964, had risen t 11.9% in 1989 8 and in 1994 was 12.7% (Russell G, persnal cmmunicatin). Other studies have shwn similar changes 9 ' 10 and a cncmitant rise in the prevalence f allergic skin sensitivity has been demnstrated. 11 We have argued that these changes in the prevalence f asthma and hay fever (and incidentally eczema) may be explained by an increased ppulatin susceptibility as a cnsequence f the recrded reductins in dietary intake f antixidants, and that changes in mite density may be less relevant. 12 It is nt illgical t argue that, if the rise in asthma were due t increased mite expsure, then the rise in hay fever shuld be explained by a rise in expsure t grass pllen. This hypthesis is directly testable, as is the hypthesis that the risk f sensitizatin is increased by cncurrent changes in the cncentratins f the majr urban air pllutants. Address crrespndence t Prfessr A. Seatn, Department f Envirnmental and Occupatinal Medicine, University Medical Schl, Fresterhill, Aberdeen AB9 2ZD Oxfrd University Press 1996
280 A. Seatn et al. Methds Burr et al. cnducted tw surveys n the prevalence f asthma amng 12-year-ld schl children in the same schls in Cardiff and the cunty f Glamrgan, Wales, 15 years apart, in 1973 and 1988. 1 They studied children wh had their 12th birthday within the current schl year (September-August). The studies had identical prtcls, using questinnaires and exercise prvcatin tests. Exercise testing was carried ut at the same time f year (April-July) n bth ccasins. The presence r absence f hay fever was determined by a questin answered by the child's parent (Burr ML, persnal cmmunicatin). We btained figures fr the prevalence f hay fever frm this paper. We have measured grass pllen cunts daily in central Cardiff since the 1950s, using a Hirst autmatic vlumatic spre trap. The twsample t-test was used t cmpare expsure t grass pllen fr the tw grups f children. Cncentratins f sulphur dixide and particulate matter (by the Black Smke methd) have als been measured n a daily basis in central Cardiff since 1962, and we btained these figures frm the Natinal Envirnment Technlgy Centre. N data fr nitrgen dixide r zne are available ver this prlnged perid in Cardiff, thugh sme sparse infrmatin is available fr ther parts f the UK. Results The prevalence f allergic diseases fund by Burr and clleagues in Suth Glamrgan in 1973 and 1988 are presented in Table 1, shwing a 59% rise in the prevalence f reprted hay fever ver this perid as well as a 118% rise in asthma and a 231% rise in reprted eczema. 1 Figures 1-3 shw the 4-mnthly average grass pllen cunts (frm May t August each year) ver the perid 1960 t 1988, and quarterly sulphur dixide and black smke cncentratins frm 1962 t 1988. Average grass pllen cunts vary frm year t year, reflecting the summer weather. The highest average cunt f 97 grains/m 3 was recrded in 1971. Table 1 Prevalence (%) f allergic disease in 12-yearld children, 1973 and 1988 Asthma: ever current Eczema ever Hayfever ever 1973 5.5 4.2 4.8 9.4 Data are frm reference 1. 1988 12.0 9.1 15.9 14.9 Difference 6.5 4.9 11.1 5.5 Between 1972 and 1982, cunts were generally lwer, the lwest value f 20 grains/m 3 being recrded in 1976. N verall increasing trend is apparent. Bth sulphur dixide and Black Smke quarterly averages shw steady and sustained dwnward trends, a cnsequence f actin taken under the Clean Air Acts f 1956 and 1968. Twelve-year-ld children in 1973 and 1988 wuld have been expsed t pllen and ambient air pllutin frm 1961 and 1976, respectively. The table cmpares the grass pllen cncentratins that Cardiff children wuld have been expsed t in the first 12 years f their lives. N significant differences were bserved fr either ttal, average r peak expsures f the tw grups f children. In cntrast, the earlier sample f children had been expsed t much higher cncentratins f sulphur dixide and particulate matter (Figures 4 and 5). Discussin It has reasnably been prpsed that the bserved increase in allergic illness is due t an increase in the amunt f allergen t which children are expsed in the dmestic envirnment, a rise in the cncentratins f huse dust mites having been pstulated n the basis f increased temperature and carpeting f huses. Althugh measurements f mites in huses were made frm the 1970s, it is nt pssible t cmpare these directly with mre recent measurements because f differences in what have been very variable techniques. Thus, n direct evidence fr r against, ver the perid in questin, is available. It has als been suggested that increases in ambient air pllutin due t increases in rad traffic r dmestic cking practices may in sme way be respnsible, and there is evidence that very high cncentratins f pllutants may increase the likelihd f allergic sensitizatin. 13 Hwever, the data n air pllutin in Britain shw prgressive reductins in particles and sulphur dixide. Mrever, althugh the measurements span a shrter perid, there is t date n cnvincing evidence f a rise in urban cncentratins f nitrgen dixide r zne, 14 making it difficult t attribute majr changes in disease prevalence t this cause. 15 As an indirect but lgical test f the 'increase in allergen' hypthesis, we have used the analgy f hay fever. While ascertainment f this cnditin in the Suth Glamrgan studies was simply by asking parents whether r nt their children had ever had the disease, it is unlikely that there wuld have been any systematic bias in the answers causing a spurius increase, hay fever having been familiar t the general public fr the greater part f the 20th century, and the results being cnsistent with thse fund in
The increase in hay fever 281 100-1 80 -\ CO 60 ^ 3 "c 8 40- c ^) " a. 20-1 1960 1965 1970 Figure 1. Average grass pllen cunts May-August, 1960-1994. 1975 1980 1985 1990 1995 7.E GO 3. 160 -> 140-60-I O 40 -I 20-1962 1967 1972 1977 1982 1987 Figure 2. Quarterly sulphur dixide averages, 1962-1994. ther studies. 8 " 10 Our results shw that the recrded 59% rise in reprted hay fever in these schlchildren between 1973 and 1988 ccurred in spite f the absence f systematic change in expsure t the relevant allergen, grass pllen, and in the presence f a substantial decrease in the main urban air pllutants, sulphur dixide and particulate matter. We are unable t cmment n the relevance f any pssible changes in cncentratins f zne and nitrgen dixide in Cardiff, since these pllutants have nly recently been measured in the area; hwever, zne is unlikely t have risen appreciably, there having been n systematic change in thse ther places in the UK, central Lndn, Sibtn and Stevenage, where it has been measured since the mid 1970s. Nitrgen dixide may have increased as a cnsequence f increases in traffic, but current cncentratins in Cardiff are generally much lwer than thse at which effects are likely, and are cmmnly greatly exceeded by thse ccurring in huses with gas ckers. It therefre seems t us unlikely that air pllutin has cntributed t the increase in allergic disease in Cardiff. While these data therefre prvide evidence that sme factr influencing the susceptibility f the ppulatin ther than air pllutin has been at wrk
282 A. Seatn et al. 140 -,.100-80 - c 60 H 8 O 40 -I 20-1962 1967 1972 1977 1982 1987 Figure 3. Quarterly Black Smke averages, 1962-1994. 160 -i 140 - "9b 100 - I 80 c 8 60 O 40 1973 chrt 1988 chrt 20 1 2 3 4 5 6 7 8 9 Figure 4. Quarterly sulphur dixide values in the first 12 years f life. 10 11 12 ver the relevant perid, the rise in hay fever recrded by Burr ef al. and by thers has been smaller than the cncurrent rise in asthma, suggesting that anther factr is likely als t be relevant t the increase in the latter cnditin. This may be simply that grass pllen is a less ptent sensitizer than the huse dust mite, but is als cnsistent with the hypthesis that children have indeed been expsed t increasing cncentratins f the latter. The mst plausible explanatin f the rise in allergic diseases in Britain and, by implicatin, in ther Westernized cuntries, is that there has been a shift in ppulatin susceptibility, pssibly amplified in the case f asthma by an increase in expsure t mites. The nset f allergic disease very early in life argues fr a pssible intrauterine r infantile change ver time having been respnsible fr the increase in allergic disease, and tw candidate (but nt cmpeting) hyptheses have been prpsed. Firstly, it has been suggested that a reductin in early childhd infectins may have resulted in a shift f the immune respnse twards an atpic ne, since evidence suggests that early bacterial and viral infectins result in a dwn-regulatin f IgE prductin. 16
The increase in hay fever 283 140 T 100-1973 chrt 1988 chrt 15 80-60 - 40-20 - 1 2 3 4 5 6 7 8 9 10 11 12 Figure 5. Quarterly Black Smke values in the first 12 years f life. Table 2 Average cunts Ttal cunts Peak cunts Summer grass pllen cunts (grains/m ) in Cardiff, 1961-73 and 1976-88 1961-1973 Mean 53.4 6570.2 679.5 95% Cl 41.6-65.2 5121.9-8018.4 367.7-991.4 Secndly, we have suggested that the substantial recrded reductin in the ppulatin's dietary intake f fds cntaining antixidants may have caused a shift in the ppulatin's lung defences, and that this may have resulted in a prgressive decrease in the resistance f successive chrts f new-brn babies t allergens. 12 Others have mre recently cme t the same cnclusin 17 and, if such a hypthesis were crrect, it culd lead t a mre practicable and effective methd f cntrlling the rise in allergic disease than effrts t eradicate mites r eliminate air pllutin. References 1. Burr ML, Butland BK, King S, Vaughan-Williams E. Changes in asthma prevalence: tw surveys 15 years apart. Arch Dis Child 1989; 64:1452-6. 2. Andersn HR, Butland BK, Strachan DP. Trends in prevalence and severity f childhd asthma. Br MedJ 1994; 308:1600-4. 3. Warner JA, Little SA, Pllck I, Lngbttm JL and Warner JO. Influence f expsure t huse dust mite, cat, pllen 1976-1988 Mean 50.4 6196.7 627.0 95% Cl 38.5-62.3 4733.7-7659.6 420.7-833.3 P 0.693 0.693 0.761 and fungal allergens in the hme n primary sensitisatin in asthma. Pediatr Allergy Immunl 1990; 1:79-86. 4. Devalia JL, Rusznack C, Herdman NJ, Trigg CJ, Tarraf H, Davies RJ. Effect f nitrgen dixide and sulphur dixide n airway respnse f mild asthmatic patients t allergen inhalatin. Lancet 1994; 344:1668-71. 5. Sprik R, Hlgate ST, Platts-Mills TAE, Cgswell JJ. Expsure t huse-dust mite allergen (Der p I) and the develpment f asthma in childhd. N EnglJ Med 1990; 323:502-7. 6. Sesay HR, Dbsn RM. Studies n the mite fauna f huse dust in Sctland, with special reference t that f bedding. Acarlgia 1972; 14:384-92. 7. Ra VRM, Dean BV, Seatn A, Williams DA. A cmparisn f mite ppulatins in mattress dust frm hspital and frm private huses in Cardiff, Wales. Clin Allergy 1975; 5:209-15. 8. Ninan TK, Russell G. Respiratry symptms and atpy in Aberdeen schlchildren: evidence frm tw surveys 25 years apart. Br Med 11992; 304:873-5. 9. Fleming DM, Crmbie DL. Prevalence f asthma and hay fever in England and Wales, fir Med; 1987; 294:279-83. 10. Lewis S, Butland B, Strachan D, Butler N, Brittn J. Cmparisn f the prevalence and aetilgy f wheezing illness at age 16 in 1974 and 1986. Thrax 1994; 49:1052 P.
284 A. 5eatnetal. 11. Sibbald B, Rink E, D'Suza M. Is the prevalence f atpy increasing? BrJ Gen PracM 990; 40:338-40. 12. Seatn A, Gdden DJ, Brwn K. Increase in asthma: a mre txic envirnment r a mre susceptible ppulatin? Thrax 1994; 49:171-4. 13. Ant JM, Sunyer J. Nitrgen dixide and allergic asthma: starting t clarify an bscure assciatin. Lancet 1995; 345:402-3. 14. Quality f Urban Air Review Grup. Urban air quality in the United Kingdm. Lndn, Department f the Envirnment, 1992. 15. Cmmittee n the Medical Effects f Air pllutants. Asthma and utdr air pllutin. Lndn, Her Majesty's Statinary Office, 1995. 16. Vn Mutius E, Martinez FD, Fritzsch C, era/. Skin test reactivity and number f siblings. Br MedJ 1994; 308:692-5. 17. Hatch GE. Asthma, inhaled xidants and dietary antixidants. Am) Clin Nurr 1995; 61(S):625S-30S.