LB 4 31 ODD EXCHANGE 8061 '12 KVf IVd *A 'M ' soig VENTILATION, WEATHER AND THE COMMON COLD A Study of the Prevalence of Respiratory Affections Among School Children and Their Association with School Ventilation and the Seasonal Changes in Weather BY GEORGE T. PALMER, M.S., Epidemiologist, Detroit Department of Health Reprint from THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE St. Louis Vol. VI, Nos. 11 and 12, Vol. VII, No. 1, August, September, and October, 1921 VENTILATION, WEATHER, AND THE COMMON COLD* A STUDY OF THE PREVALENCE OF RESPIRATORY AFFECTIONS AMONG SCHOOL CHILDREN AND THEIR ASSOCIATION WITH SCHOOL VENTILATION AND THE SEASONAL CHANGES IN WEATHER BY GEORGE T. PALMER, M.S., EPIDEMIOLOGIST DETROIT DEPARTMENT OF HEALTH INTRODUCTORY DURING the last twenty years there has been a great amount of experimental work on ventilation and its effect on the body. Workers in Europe and the United States are in substantial agreement that it is the thermal factors temperature, air motion and humidity which exercise the greatest influence on human comfort, health and efficiency. The chemical composition of the air we ordinarily breathe leaving out of consideration for the moment those special industrial problems involving gases, fumes and dusts is of relatively little moment in its effect on human conduct. School children are far better off in a cool, airy room, regardless of the carbon dioxide content of the air, than they are in air virgin pure chemically which is overheated. It is most important that the facts as we have stated them should be clearly understood, for otherwise, there is bound to arise, as there has in the past, a misunderstanding as to the suitability of different methods of ventilating school buildings. If variable, as opposed to uniform, temperature, air motion and humidity are desirable factors, then very satisfactory conditions can be maintained in school rooms by ventilating with the windows, protected by deflectors, and an exhaust duct on the opposite side of the room, heating being by direct radiation beneath the windows. This method of ventilating will not always give good aeration. At times the room will be amply flushed with outside air. At other times, due to shifting winds, the circulation will be lessened, the room will not be thoroughly flushed, and the carbon dioxide content will rise, indicating an accumulation of the products of exhalation and body vaporization. Even though the aeration of the room fluctuates, it is possible to have coolness at all times and variability, and if the room is cool and *This is an abridged form of a dissertation presented in partial fulfillment of the requirements for the degree of Doctor of Public Health at the University of Michigan, 1920. > This study was conducted jointly by the Bureau of Child Hygiene of the New York City Depart- ment of Health, represented by Dr. S. Josephine Baker, Chief of the Bureau, and "the New York State Commission on Ventilation, represented by the author, who then held the position of chief of the in- vestigating staff. The collection of sickness records and the taking of temperature and other observations on air conditions was done by nurses and physicians of the Health Department under the supervision of Drs. L. Marcus and R. H. Willis. The routine clerical work of tabulation was likewise conducted by the Health Department under the immediate direction of Dr. Franklin Van Wart. The planning of the investigation, selection of schools, initial instruction of the field staff and the final analysis and interpreta- tion of results is largely the work of the author. 507568 3 variable ,wMriii':(>e?taiii.limits.i"t makes little practical difference as to the humidity. On the other hand, if the experimental data of the last two decades are wrong in minimizing the relative value of chemical purity of the atmosphere, then window ventilation as we have described it is inadequate, and it will be necessary to insure at all times voluminous and continuous flushing of the room with outside air. This can be done only by mechanical means, that is by plenum fans or blowers. There has existed for some time a controversy as to the relative merits of natural and mechanical ventilation. An inheritance from the days of Pet- tenkofer, when chemical purity was regarded as vital, has kept alive the carbon dioxide content as the standard of ventilation goodness. This standard persists to this day. Measured in these terms the window venti- lated room falls into disrepute. A carbon dioxide standard of 6 to 10 parts per 10,000 automatically throws any form of window ventilation into the dis- card. It is only by mechanical means that this degree of chemical purity can be at all times assured. With the development of mechanical ventilation there has grown up an impression that uniformity in temperature, in air motion and in humidity is ideal, and again the mechanically forced ventilation far excells the gravity method in this respect. Furthermore the dust in outside air can be removed readily under the mechanical system by the introduction of air washers. This is not possible with window ventilation. There is much then that can be accomplished with the plenum system that is not possible under the window method. The question arises as to whether the superiority of the mechanical system is superficial, a matter of a relatively unimportant refinement so far as the school classroom is concerned. The drawbacks to the mechanically ventilated classroom are its tendency to over- heating, its unstimulating uniformity and its greater expense. There is much to be said on both sides. The advocates of window ventila- tion are impressed by its success with tuberculously inclined and undernour- ished children. It has a wide application in our public schools at the present time. If good for sick children, why not for well children? Is window ven- tilation in the schoolroom to be ruled out of consideration merely because it fails to live up to the carbon dioxide standard? It was for the purpose of testing out these principles on a practical scale that the present experiment was undertaken. After all, the proof of the pudding is "hi the eating. If the health of school children, as measured by the amount of respiratory illness, such as colds, tonsillitis, etc., is better under the more elaborate systems of mechanical ventilation, then let us proceed to equip our buildings in this manner. If, on the other hand, the mechanical ventilating equipment does not supply substantial benefits to the health, comfort or efficiency of our school child population, or is actually inferior in the things that count for health, let us face the matter squarely. There are innumerable demands for public funds. If we are paying out vast sums of money for benefits which are not real but imaginary, recognition of this fact cannot come too soon. If window ventilation provides the im- portant essentials of a healthy atmosphere in a way that cannot be attained or improved upon by mechanical systems of indirect ventilation, then our school buildings should be built accordingly, and we should not hesitate because a worn out standard of ventilation dictates otherwise. During the latter part of 1916, from February 14th to April 6th (8 weeks), and the winter of 1916-17, from October 30 to January 26 (12 weeks), observa- tions were made on the health of 5500 New York City school children who were exposed to various types of ventilation in 12 different school buildings. In general these ventilation systems may be classified under three main headings, as follows: A Cold, open window rooms, gravity exhaust. B Cool, window ventilated rooms, gravity exhaust. C Plenum, fan ventilated rooms with gravity exhaust and with windows closed. As an index of health, the sickness records of the pupils w^ere used. The condition of the air was determined by readings of temperature and humidity and by the personal sensations of the observers as to temperature, moisture, air motion and odor. It would have been desirable to determine also the carbon dioxide content of the air, but this involved analytical work which the staff was unable to do. The absence of these latter data was not serious, however, for the Ventilation Commission had available a mass of data on this subject collected over two years' time, and it was well established that the carbon dioxide content of fan ventilated rooms averages several parts lower than in window ventilated rooms. For the convenience of the reader we shall reserve the description of work- ing methods and ventilation types in individual schools for the later pages and shall proceed with an account of the findings of this study. RESULTS OF SICKNESS SURVEY IN DIFFERENT TYPES OF VENTILATED SCHOOL ROOMS The first half of the study in the spring of 1916 covered 2500 pupils in 58 classrooms distributed among 8 schools. The second half in the winter of 1916-17 was represented by 3000 pupils in 76 classrooms in 12 schools. In both studies the absences due to respiratory illness and the respiratory illness among pupils present in school was greatest in the fan ventilated rooms, Type C. This is the result after combining all records and disregarding in this instance the balancing of the type of pupil, location of school, etc., which will be treated more at length later on. The excess of respiratory illness in the Type C rooms holds good both for absentees and those in school. The total illness is least in the second group, or cool, window ventilated rooms. The difference, however, between the first and second types of window ventilation is less than between either the first or second and the third. In other words, assuming for the moment that these differences are due to atmospheric influences, the air conditions in the first two types do not produce greatly divergent effects, but the influences at work in the third type are distinctly less favorable. The significance of these two sets of results may be expressed in this man- ner; for every 100 cases of respiratory illness in the cool window ventilated rooms, there are 152 in cold, window ventilated rooms; and 231 in fan venti- lated rooms. TABLE I RESPIRATORY ILLNESS PER 1000 REGISTRATION (PUPIL-SESSION) UNITS* Ventilation Type FIRST STUDY Among Among Absentees- Pupils Total SECOND STUDY Among Among Total Absentees Pupils in School in School A-Cold, Window Rooms 10.6 37.2 47.8 9.2 75.3 84.5 B-Cool, Window Rooms 10.2 22.1 32.3 10.7 44.1 54.8 C-Fan Ventilated 14.2 76.0 90.2 13.0 98.4 111.4 TABLE II BASIC FIGURES FROM WHICH RATES IN TABLE I ARE COMPUTED FIRST STUDY h- .8" SECOND STUDY o -g *s - .g.s .- "3 3 J.S 02 &r2 t 05 &r2 & || ^1 | "S DQ O '^< ^ EH 3 i fl Q 02 S 1 || ^ gD | a S K^ K J-H r2 O ..j_, Q *s c ID rt g 'So rQ O i s P * S |rf OQ fl '& 3 rt'EL -M OQ ^ S r^ 3 O o O 0? - "O pS fl . o O HM -2 EH M -2 A 61,658 655 2,298 89,067 822 6,705 B 71,231 728 1,578 113,959 1,218 4,661 65,088 925 4,950 115,215 1,497 11,329 The actual temperature conditions found in the three types of rooms are disclosed in the two tables following, in one of which results are expressed as averages, and in the other by temperature groups. TABLE III AVERAGE OF ROOM TEMPERATURES Ventilation Type First Study Second Study Mean A 58.8 59.1 59.0 B 66.9 65.9 66.4 C 68.8 67.9 68.4 *The unit of illness was one pupil per half-day school session. Illness is reported in pupil session units. One pupil ill ten sessions counted the same as ten pupils ill one session. A pupil was continued on the register regardless of the length of absence from school unless it was found that the family had moved away from the school district, or that the pupil had left school permanently. Separate tabulations have been made of illness resulting in absence from school and illness among pupils who continued to attend school. The absences are classified as (1) absence from respiratory illness, including coryza, bronchitis, pharyngitis, laryngitis, tonsillitis, pneumonia, tuberculosis and a miscellaneous group variously termed grippe, colds, sore throat, etc.; (2) absence from illness other than respiratory, namely: stomachache, backache, broken leg, etc. In this group were also the acute infectious diseases such as diphtheria, measles, scarlet fever, whooping cough, chickenpox, mumps, etc. This was done be- cause it was felt that the spread of these infections was largely determined by specific susceptibility rather than by atmospheric influences; (3) absence due to causes other than illness, such as staying at home to mind the baby, going on a visit, shopping with parents, truancy, etc. The fan ventilated or Type C rooms averaged but two degrees higher than those of Type B and nearly ten degrees warmer than Type A. Type A was extremely cold for a school room. Type B was cooler than is cus- tomarily found. The average temperature of Type C, though higher than B, was not exceptionally high. There was a wide range in the daily temperatures, which are lost sight of in the averages. TABLE IV FREQUENCY DISTRIBUTION OF TEMPERATURES PER CENT OF SESSIONS Types Ventilation 59 and below 60-69 . 70 and over 1st Study A 56 41 3 B 5 61 34 C 4 57 39 2nd Study A 46 48 6 B 8 88 4 C 0.2 99 0.8 The A rooms rarely reached 70. Fully half of the sessions were below 59. The B and C rooms rarely fell below 60. The temperatures in the second study were much more uniform, particularly as regards Type C and to a lesser extent Type B. More than one-third of the sessions in B and C in the first study were above 70. Much of this represented an overheated condition. However, the first study was made in the late winter, when greater outdoor variation is experienced than from November to January. Although the pro- portion of sessions between 60 and 70 does not appear to differ much in the B and C rooms, yet there was an appreciable difference within this range. Thus, in the first study 24 per cent of sessions in B were from 60 to 64, whereas but 6 per cent of the sessions in C were within this range. Thirty- seven per cent of B sessions were from 65 to 69 as against 51 per cent of the C sessions. The C rooms were warmer, as the averages have already indicated. The interesting point to be noted is that whereas there was but two de- grees difference in temperature between the B and C rooms, there was a wide difference in the sickness rates. Between 7 and 8 degrees separated Types A and B, and yet in spite of this the sickness rates were quite similar. Evi- dently some factor other than temperature operated differently on these three classes of rooms or else a rise of two degrees above 66 is far more conducive to colds than a drop of as much as 7 degrees. HUMIDITY The relative humidity ranged from 38 to 46% and did not differ greatly in the three classes. As would be expected, the relative humidity was higher in the colder rooms. With the same amount of moisture present as in Type A, the relative humidity in the first study at the temperature in Type B would be 33.4, V RELATIVE HUMIDITY Ventilation First Study Second Study Type A 43,7 46.3 B 37.8 43.0 C 37.8 41.2 and in Type C 31.4. The corresponding figures in the second study would be 29.9 for B and 28.7 for C. It would appear, therefore, that there was an accumulation of moisture in the Type B rooms, and this could only come from reduced aeration. In Type C the same explanation would hold. The rooms at P. S. 59 were humidified, as were also the rooms at P. S. 51 and 97, but this would hardly affect the average of all rooms in the group to this extent. It is also possible that the taking of the humidity reading was not as accurately done in the dry rooms, the wet bulb being read before the mer- cury column had completed its fall. These readings are higher than we should expect at this season of the year, judging from records taken by the Com- mission in similar rooms in other schools. Other indices of air conditions were the opinions of the nurses who visited the rooms at least twice daily. FRESHNESS AND ODOR The results of the nurses' votes on the freshness or lack of freshness and presence of odor in the rooms are given in Table VI. TABLE VI PERCENTAGE OF SESSIONS JUDGED Ventilation Exceptionally Odor Absent but Type Fresh not Exceptionally fresh Odorous First Study A 62 B 25 C 21 Second Study A 69 B 18 C 22 24 57 64 28 62 67 14 18 15 3.2 20 11 The results are very interesting from several points of~view. The Type B rooms are most odorous in both studies. The excess over the others was slight in the first study, 18, as compared to 15 for Type C and 14 for A. It was more marked in the second study, 20, as against 11 for C and only 3.2 for A. The freshest rooms are the coldest rooms. Sixty-two per cent of the sessions in Type A in the first study were judged exceptionally fresh, and in the second study the figure was 69 per cent. The figures for Type B were 25 per cent in the first and 18 in the second. Type C had 21 per cent in the first and 22 per cent in the second. 8 What seems clear from these figures is that to be exceptionally fresh the greater part of the time, rooms must be well below 65 degrees in temperature. Warmer rooms may be free from odor and yet exceptionally fresh not much over one-fifth of the time. In rooms that did not differ greatly in temperature, as B and C, the greater aeration produced by fan ventilation reduced odor to a slight degree in the first study, and to a marked degree in the second. It failed to make the rooms any fresher in the first study, but did help out in the second study. Although we do not possess complete records of the carbon dioxide con- tent, there is little doubt but that the smallest amount would be found in the fan ventilated rooms, Type C, as we have already pointed out. Repeated records collected in three schools show this tendency (Table VII). TABLE VII CARBON DIOXIDE IN PARTS PER 10,000 SCHOOL VENTILATION TYPE B C 33 115 97 6.9 5.5 7.6 6.5' 8.6 5.7 The markedly greater freshness of the Type A rooms is due, without ques- tion, to their low temperature, and not because of the greater chemical purity of the air. Freshness is not a question of odor, for the Type B rooms were fresher than C and yet more odorous. SENSATION OF TEMPERATURE The recorded votes of the nurses as to whether the temperature of the rooms felt "too cool," "satisfactory" or "too warm" are given in Table VIII. TABLE VIII VENTILATION TYPE PER CENT OF SESSIONS JUDGED TOO COOL SATISFACTORY TOO WARM First Study A 7.9 77 16 B 6.2 78 16 C 10 76 14 Second Study A 26 70 3.9 B 8.6 80 11 C 3.6 85 12 In the first study the per cent of satisfactory sessions was about the same in all three types, being in the neighborhood of 77 per cent. There were more sessions judged "too warm" in Types A and B than in C, although the average temperature was lower than C. The "too cool" sessions were most numerous in Type C, the rooms of highest temperature. In other words, the coldest rooms felt warmer than the warm rooms. In view of the actual temperature found, it would appear that the nurses were influenced in their judgment of what the temperature should have been rather than by actual sensation. In no other way can we account for the votes in rooms whose temperature differed by at least ten degrees, as was the case in Types A and C. The votes in the second study more nearly reveal the actual temperature condition as indicated by the thermometer. In A 26 per cent of the sessions were judged "too cool." In fact, 4 per cent were voted "too cold" an ex- treme condition. In Type B, 8.6 per cent were "too cool" and in C 3.6 per cent. Type C had the greatest number of sessions judged satisfactory as to tem- perature; namely, 85 per cent. The corresponding figure for Type B was 80 and for A, 70. Too great warmth was experienced 12 per cent of the time in C, 11 per cent in B and but 3.9 per cent in A. The sensation of temperature reflects the actual thermometer reading to some extent at least. There was much lesss overheating in the second study, and this agrees with the lesser number of "too warm" votes. SENSATION OF MOISTURE As will be seen from the figures given below, over 80 per cent of sessions in all three types of the first study were judged satisfactory as to moisture. Both moisture and dryness were most pronounced in Type C. TABLE IX VENTILATION TYPE PER CENT OF SESSIONS JUDGED MOIST SATISFACTORY DRY First Study A 5.9 88 6.7 B 1.7 89 9.0 C 7.3 83 9.7 Second Study A 33 66 0.6 B 20 74 6.4 C 8.5 84 7.9 The second study reveals a greater divergence between the rooms. Type C had the highest percentage of satisfactory sessions, 84. Type B had but 74 per cent and Type A, only 66. The cooler sessions are associated with moisture, the warmer sessions with dryness. " One-third of all sessions in A were moist and less than 1 per cent dry. Twenty per cent of sessions in B were moist and 6.4 per cent dry. Eight and five-tenths per cent of C were moist and 7.9 per cent dry. There was less overheating in the second study and the sensation of dryness is less. Type C is similar in both studies. The other two types are different in that the second study shows many more moist sessions. AIR MOTION The greatest proportion of satisfactory votes as to air motion was found in A. Moving air was noticed most frequently in A and least in B. The results 10 of both studies are similar, although it is surprising to find the sessions in Type C judged "dead" to be more numerous in the second study where the air flow through the rooms was greater and the temperature was lower. TABLE X PER CENT OF SESSIONS JUDGED VENTILATION TYPE DEAD SATISFACTORY BREEZY First Study A 4.7 81 14 B 15 78 7.1 C 9.3 73 18 Second Study A 9.2 74 17 B 18 75 7.0 C 23 68 9.8 ANALYSIS OF SICKNESS RATES IN INDIVIDUAL ROOMS AND SCHOOLS A S we have pointed out in the introductory remarks, great care must be ** taken in drawing conclusions as to the correlation of different facts from the average results of a group. In the study before us it will be necessary to inquire into the records of each school and of the individual rooms to see whether they agree uniformly with the characteristics of the group. In Tables XI and XII are assembled records for each room covering the nature of air conditions and the amotint of respiratory sickness. It is noticeable that there is a wide variation in respiratory illness. Room 415 (Type B) at P. S. 22 in the second study had no absences whatever from respiratory illness. Room 311 (Type C), P. S. 115, in the second study, has a rate of 50.4. These represent the minimum and maximum limits. The range of respiratory sickness-in-attendance rates is even greater from zero to 316. Room 311, P. S. 59 (Type A) is the most congested in the first study, there being but 6.5 square feet of floor space per pupil. In spite of this crowded condition, the absence rate from respiratory disease is only 0.6 one of the lowest. On the other hand, Room 202, P. S. 165, being the least con- gested, with 19.6 square feet per pupil, has a respiratory absence rate of 37.0, a very high figure. Overcrowding does not inevitably lead to respiratory illness. The average temperature of Type A rooms was about 59 degrees in both studies. This is much colder than the ordinary school room. In fact, it seems from our general experience entirely too cold for public school children, and yet, on looking over the absence rates, there is no indication that these children had more colds as a result. In fact, the average absence rate for the entire group is lower than the other two ventilation types, as has already been pointed out. In the first study there are only two rooms in Type A with rates over 20. There are three each in Types B and C. Respiratory sickness among those present in school is greater in Type A than in B, but less in A than in C. 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REL. HUMIDITY PER CENT W H 5 Q PH O W Q 03 H 00. Type A Cold Open Window Eooms 12 303 3.9 46.6 50.7 59.9 58.0 28 2 A 409 8.1 13.7 21.8 61.3 54.4 18 4 B 410 11.1 14.2 25.3 60.3 56.0 33 4 B 39 202 6.9 65.0 71.9 58.7 41.3 65 4 3 A 203 13 40.0 53.0 56.2 43.4 72 2 4 A 204 21.6 45.9 67.5 56.6 43.1 72 1 3 B 205 6.7 30.3 37.0 58.7 42.2 46 7 3 B 206 9.3 24.9 34.2 58.3 40.3 55 3 A 207 11.7 18.4 30.1 57.6 41.4 60 2 4 B 59 308 4.0 165 169 60.0 48.0 100 3 B 311 8.5 144. 152.5 58.5 48.9 100 3 A 313 26.8 213 239.8 59.0 44.7 85 11 2 A 412 4.3 150 154.3 58.1 45.1 100 4 A 413 9.2 147 156.2 60.0 48.0 98 2 4 B 414 3.0 124 127 57.8 48.4 100 4 A 416 8.0 91.3 99.3 57.6 46.5 100 4 B 73 301 5.1 44.1 49.2 60.2 44.8 71 2 5 B 309 11.6 34.8 46.4 58.9 45.9 67 2 4 A 402 6.1 18.4 24.5 60.5 44.7 72 5 6 A 403 6.2 39.4 45.6 63.5 45.3 50 29 5 B Type B- -Moderate Temperature, Open Window Eooms 2 Bx. 301 10.7 9.7 20.4 68.6 38.5 13 2 B 302 7.7 5.8 13.5 69.0 38.5 23 2 B 316 11.6 12.2 23.8 65.4 40.0 24 5 A 12 405 9.5 33.2 42.7 62.2 57.8 6 1 4 A 408 15.9 31.4 47.3 63.5 59.0 1 2 3 B 12 411 9.9 5.8 15.7 63.8 60.6 3 10 4 A 22 415 67.6 57.7 17 82 5 B 416 5.5 2.7 8.2 68.2 56.0 23 72 6 A 418 .9 24.6 25.5 67.3 56.7 29 65 5 B 33 Bx. 13 21.4 55.7 77.1 69.3 31.3 9 8 B 23 27.5 47.5 75.0 69.4 37.2 1 21 7 A 39 302 10.9 33.6 44.5 63.0 40.3 19 4 A 308 8.6 42.8 51.4 65.0 37.7 23 3 5 A 408 2.9 58.0 1 60.9 65.2 39.0 9 31 5 A 59 318 3.7 187 190.7 64.9 48.5 4 61 3 A 415 16.2 158 174.2 58.8 48.2 100 4 B 73 305 9.7 23 32.7 61.6 46.5 45 10 4 B 406 2.7 41 43.7 67.1 43.3 17 35 3 A 408 16 51 67 61.1 43.6 74 ' 4 3 B 97 302 6.4 37 43 67.0 38.2 17 62 5 B 313 7.1 50 57 67.3 41.8 71 17 4 A 501 3.0 55 58 65.9 44.8 59 18 6 B 115 312 23.3 67.8 28.8 3 3 4 B 502 40.2 67.9 26.2 2 3 5 B TABLE XII (CONTINUED) RESPIRATORY SICKNESS RATES M rn O PER CENT H SESSIONS ri ^ , co 1 jri Is III a PH 1 |i M K CQ f H O I o o II |sE! g > ^ PH* CO cs CO <1 H < S D n. c sl PI J: t. o> a < &,. / V \ \ ^ ~J7 \V / \ ^ \ ^ J /; ^^ \ \ ^ \> -,^ J v\\ i ^ */ '\N // \\ - x I "^" \ /- 1 f tLATIVE HUMIDITY IN CLASSROOMS 1 L " x < / 1 1 WEEKLY INCIDENCE OF TOTAL RESPIRATORY ILLNESS IN CLASSROOMS VARIOUSLY VENTILATED Data from a/1 schools included t ACept 97, 115, 31 Bx ^ A- Cold, wi- Jo* venti atd rooms (about 5 ) B- Cool, window vent,latd room* (about 65*) C- fan- ventilated room* (about 69'} Chart IV. during the last seven weeks of the second study. The fan ventilation group shows the greatest amount, and the window ventilated, moderate temperature, the lowest amount of respiratory illness throughout. Respiratory illness declines from February to April although the fan ven- tilated rooms show the highest point during the middle of March. Colds 34 are at a higher level in October than they are in April. In the Type C and B rooms colds increase abruptly during the first 5 weeks in the Autumn. Type C then holds this level. The B rooms fall off and do not rise again until January. Colds in the Type A rooms increase gradually from October till RESPIRATORY ILLNESS AMONG- SCHOOL CHILDREN AND IT'S ASSOCIATION WITH THE. WEATHE.R By Weeks FIRST STUDY StCOND STUDY 8weeks Feb 14,- Apr. 6,l9ife I2*veeks Oct. 30, 1914,- Jan 26, (917 90 70 50 JO 90 75 60 45 TO, ^ . "-**. *- ,^-= .--* ^^< N, -~~" ^ -\ OUTDOOR WEATHLR RECORDS / , j 7 "--. _..-' *.. *' '' " ^. "*N. *= % x 30 70 u 50 40 30 Ik Mean Temper-afore iQAM-PM ^-^1 i^-^ * ^ ^ k x "^-x. \ / N / \ X \ 7 \ ^J / \ 7 N^ 1\ 7 \ ^ \ I \ Per Cent of Fbasible Sunshir J V / V J , \ V veroge Change inTe -npcraturel S 70 65 fed 55 50 6 5 3 2 10 8 I / \ 1 V x \ \ X ^^ K-*"^ h "v. ^^- - ^X ^^~ ^ I 1 I MQ^ Relative Hun n.dily -> 7 ^vj^. \- / \ \ / ^ s x ./* Ny 7 \ Lx \ 7 ^^ X 7 V y \ 2T ^ y / 'X \ ^s ^ IV N N j V \ \ . '****^ 1 \ \ \ / \ ( fMeon Hours Roin or SnowfoJ I pr dc^ ^v -\- -/- \^ > i^*- ^^^ ^^ "S x- s^^ S. / ^s ^^ x^ Mon Do. Iv W.nd Velocity Chart V. the first week in December. From this point they decline only to rise again the latter part of January. Room temperature in the fan ventilated rooms is the most uniform, keep- ing quite constantly between 68 and 69 degrees. In the window rooms Type B, temperature has a slightly wider variation, from 65 to 68 degrees, but is consistently below Type C. In Type A rooms we note a wide variation, 35 from 55 to 66. During February and March these rooms run between 50 and 60, and this is true also in December and January. In April and Novem- ber the temperature is from 60 to 65. Kelative humidity is greatest in the A rooms. It is lowest in March and January. As will be seen from a later chart, humidity is influenced mostly by outdoor temperature and next to that by outdoor moisture. Total Respiratory S/ckness Pate. Weather Corn fort Vote. 8 RESPIRATORY ILLNESS, WEATHER AND THE SENSATION OF WEATHER Mean Outdoor Temperature Total Deheating Potver <*^ \Heather~ The general points to be noted from this chart are that colds are more common in fall than in late winter, that even though the room temperature and humid- ity in Types B and C are quite similar, there is an appreciable difference in the prevalence of colds, and finally that the course of respiratory illness from week to week is guided mainly by influences other than the temperature and humidity of the classroom. 36 That outdoor weather bears a close relationship to colds is illustrated by the various graphs on Chart V. Far overshadowing other weather in- fluences is temperature. In the spring, colds decrease as the weather becomes warmer. In the fall, oncoming cold weather is coincident with increasing respiratory affections. V ^ / -^ i ~ 1 6O ^^* ^ ' ^_ -*. ^ 40 Mild Cole 3 m Not"! suffic lent t i caus abs< nee i rom schoo |. Week Ending 3 10 n 24 1 8 15 22 5 \Z \9 fJb, MOV ^ DEC JAN. u? / ^ ^ ^5^ / \ / 4 . -: ^ Sever e Co ds On LSI Q _absc. vce o rom scho ol. Week Endmo 3 >0 7 Z4 -l 8 |5 NOV. DEC. 22 5 12 19 2fc ,c 00 DeatKa from Pneumonia n w Y/// % i, OCT NOV. DEC THE SEQUENCE OF COLDS AND PNEUMONIA JAN. NEW YORK CITY 1916-1917 Colds among 3000 school children expressed as a rate per 1000 pupil session registration units. Total deaths from pneumonia (all forms) in New York City. Chart VII. What is understood as changeable weather does not have marked influence on colds. The third week in February shows an extreme daily change in temperature with no accompanying increase in colds. Relative humidity shows wide variations from week to week without corre- 37 spending undulations in the sickness curve. The late winter is more blus- tery than the fall, and yet colds are less numerous in the windy season. Temperature and colds are most closely related. Is it temperature per se or the total chilling effect of all weather elements combined? The formula derived by Dr. Leonard Hill of England from his instrument known as the kata-thermometer permits us to sum up in a single expression the combined deheating effect of cold, evaporation and wind action.* From the mean daily outdoor temperature, vapor pressure and wind velocity we have com- puted the mean " total H" or total deheating power of the elements. This graph has been placed alongside curves for respiratory illniess in the second study, and mean temperature and a fourth curve labelled " comfort." The comfort vote is a summary of the recorded daily impressions of the tem- perature feeling of the weather, as judged by three members of the staff of the Ventilation Commission. The kata and temperature curves closely parallel each other. In some respects the kata curve is more closely associated with the rise and fall of illness than the temperature curve. Thus, the kata curve shows increasing cold for the first four weeks corresponding to increasing illness. The tem- perature curve shows no increase in cold in the fourth week over the third. Illness falls off as the temperature stabilizes. In the 7th week tempera- ture again descends, and sickness picks up. The 10th week is much colder as judged by the kata reading although the temperature is no lower. There is however, very low humidity and high wind velocity, which are heat extrac- tors. These data suggest that it is the total chilling effect of the atmosphere rather than low temperature alone that is conducive to illness. The curve of outdoor temperature comfort closely parallels the temperature curve, more so than the kata curve. The sequence of mild colds in November, followed by heavier colds in December and then by pneumonia in midwinter, is strongly suggestive of a progressive weakening of vitality. Our mid-winter pneumonia peak is thus the result of attrition of vital resistance caused, among other things, by acute respiratory affections in the months preceding. SUMMARY AND CONCLUSIONS Prom the results of this study there appears to be something inherent in the indirect method of ventilating schoolrooms by means of forced draught and gravity exhaust, as practiced in this study, that is productive of respiratory affections, something which is not present in rooms ventilated with windows and gravity exhaust. What these unfavorable elements are is not entirely clear. Higher temperature is one. Uniformity of temperature and air flow is another. Uniformity is characteristic of the fan ventilated room. In an unvarying atmosphere the occupants miss that pleasant stimulating effect. Evidently the absence of this quality affects health adversely as well as comfort. *"The Measurement of the Rate of Heat loss at Body Temperature by Convection, Radiation and Evaporation." By Leonard Hill, F. R. S., O. W. Griffith and Martin Flack, Philosophical Trans- actions of the Royal Society of London. Series B. Vol. 207, pgs. 183-220. 1916. 38 The temperature of window ventilated schoolrooms may be reduced as low as 59 degrees without increasing the prevalence of colds. It must not be inferred that window ventilation- as represented in this study was uniformly satisfactory. It was not. As a rule the rooms exposed on the east do not fare as well as others. Ample exhaust openings are better than those of small area. There is the matter of location of outlets with respect to the windows, location, size and control of direct radiation, window deflectors, etc., which affect the success of window ventilation. All of these factors must be studied. In spite of our inadequate knowledge of window ventilation at its best, the fact remains that the window rooms of this study, even though of crude arrangement and not built originally for the purpose, competed on favorable terms, from a hygienic and aesthetic standpoint, with the most elaborate and costly fan and duct equipment. The tendency in the past twenty years has been away from natural and toward mechanical ventilation. The time and effort of the heating and ventilating engineer has been directed toward the perfecting of mechanical means for aerating buildings. What would the same amount of effort have yielded if expended on the development of natural ventilation? Possibly something of great value and at less expense. Because window ventilation is practicable for the ordinary schoolroom, it does not follow that the assembly room, the theatre and other places seating several hundred people can also be dealt with in this manner. Each type of enclosure must be handled as a distinct problem. Natural ventilation has its limitations. That the schoolroom is not beyond these limitations is the indication of this study. The factors which, above all others, promote comfort, health and effi- ciency are coolness and fluctuating air motion. If the teacher maintains her classroom in a changing condition, without draughts, between 64 and 70 degrees, with the mean lying nearer the lower figure, it matters little from a practical standpoint what the other measurements of ventilation indicate. To this standard the room properly equipped with window ventilation and gravity exhaust, can readily conform. In its quantitative effect on respiratory illness school ventilation is of much less moment than the outdoor weather influence. Respiratory affections increase with the onset of cold weather. They diminish with the advent of mild weather in the spring. Wind and humidity accentuate the temperature in- fluence. Sunlight exerts at least a warming influence sufficient to modify the unfavorable effect of cold. Abrupt changes in temperature do not in- fluence respiratory illness as much as one might expect from everyday experience. The sanitarian is interested in the prevention of the tremendous increase in the mortality from the pneumonias, which occurs in cold weather. If it is possible to mitigate the unfavorable weather effect by the proper regulation of the indoor atmosphere, it behooves the public health fr&ternity to bend every effort toward this goal. The problem is an alluring one. The results of this school study hold forth much promise in this direction. 39 THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW AN INITIAL FINE OF 25 CENTS WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. THE PENALTY WILL INCREASE TO SO CENTS ON THE FOURTH DAY AND TO $1.OO ON THE SEVENTH DAY OVERDUE. JAN 21 1&J3 It JUL082004 1939 tP DEC 27 1943 FEB 19 LD 21-50} 507568 UNIVERSITY OF CALIFORNIA LIBRARY