Tobacco Smoke Habits in a Group of Adolescents: Responsibility ofthe Cohabitants in the Active and Passive Exposure1

Roberto Bono,* Walter Arossa,† Enzo Scursatone,* Valeria Meineri,* and Giorgio Gilli*

*Department of Public Health and Microbiology, University of Turin, Turin, Italy; and †Dispensario di Igiene Sociale, USL VII,Turin, Italy

Received August 8, 1996

Several studies in adults demonstrated a positiverelationship between the number of cigarettessmoked and the urinary cotinine. The aim of thiswork was to analyze the passive and active smokingexposure of 333 sixteen-year-old students, demon-strated by their urinary cotinine, in comparisonwith the smoking habits of all the cohabitants. Thislast information was obtained from a questionnaireand urinary cotinine in mothers. The second pur-pose of this work was to observe whether the smok-ing habits of parents can promote the voluntary ac-tive exposure to tobacco smoke in children. Theconsidered students represent a particular group ofpeople (16 years old) having a life-style still strictlybound to the smoking habit of parents. In fact, thenonactive smokers show urinary cotinine levels de-scribed by the following means: 28.81, 39.35, 39.62,and 57.67 ng/mL. This finding demonstrates a trendof exposure from no exposure to a maximum level ofpassive exposure. Similar results can be observedby considering the urinary cotinine of mothers. Fi-nally, the active smoking habit potentially acquiredby the adolescents seems to be induced also by emu-lation of the smoking habits of fathers. This possi-bility is demonstrated by a light positive and statis-tically significative correlation with the number ofcigarettes actively smoked and, consequently, withurinary cotinine. © 1997 Academic Press

INTRODUCTION

Among the general population, smoking rateshave steadily decreased over the last decade. How-ever, cigarette smoking continues to be a significantproblem among adolescents and large sectors ofadult populations. Furthermore, passive smoking,which has been classificated by the EPA as a class A

carcinogen (U.S. Department of Health and HumanServices, EPA, 1993), is the major source of indoorpollution.

The relationships between smoking habits ofadults and environmental tobacco smoke (ETS) ex-posure of their children have been recognized bymany authors (Townsend, 1991; Stone, 1992; Lead-erer, 1990; NRC, 1986; Willers, 1992; Chilmonczyk,1990; Henderson, 1989; Coultas, 1990), but, exclud-ing Pirkle (Pirkle, 1996), only using an administeredquestionnaire and evaluating the number of ciga-rettes smoked by parents.

Cotinine, an important metabolite of nicotine, hasbeen shown to be very specific and sensitive indica-tor of ETS exposure (Matsukura, 1979; Benowitz,1996) having a half-life of about 20 hr. Several stud-ies in adults have demonstrated a direct relation-ship between the number of cigarettes smoked andthe urinary level of cotinine (Matsukura, 1984; Hoff-man, 1983). The utility of cotinine as an indicator ofETS exposure in children has also been studied byGreenberg (Greenberg, 1984); he found a high cor-relation between an estimate of ETS exposure in thehome and urinary cotinine levels, well reflecting itsrole as an internal dose marker.

The presence of this metabolite in body fluids canbe detectable also in the majority of nonsmokers(nonactive and nonpassive): for example, a study ofurinary cotinine (Repace, 1990) in 663 U.S. never-and ex-smokers showed that 91% of the subjects haddetectable concentrations, averaging about 10 ng/ml. Finally, it can be assumed that cotinine is a sen-sitive and specific internal dose marker for tobaccosmoke exposure.

The aim of this work was to analyze the passiveand active smoking exposure of 333 sixteen-year-oldstudents (15.88 ± 0.6), demonstrated by their uri-nary cotinine, in comparison with the smoking hab-its of all the cohabitants. This last information was

1 This study was conducted in accordance with national andinstitutional guidelines for the protection of human subjects.

ENVIRONMENTAL RESEARCH 75, 95–99 (1997)ARTICLE NO. ER973761

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0013-9351/97 $25.00Copyright © 1997 by Academic Press

All rights of reproduction in any form reserved.

obtained using the answers to an administeredquestionnaire and the dosage of urinary cotinine inmothers. The second purpose of this work was toobserve whether the smoking habits of parents canpromote the voluntary active exposure to tobaccosmoke in adolescents.

MATERIALS AND METHODS

Epidemiological Sample

The construction of the epidemiological samplewas started by choosing three districts of Turin city.In each district all the high schools were identifiedand using a random method one school was chosen.Subsequently, from 408 students attending the sec-ond year of studies in the three schools chosen, 330accepted to participate (81.6%). One school at a timewas considered, and the whole work of samplinglasted 3 months, from December 1992 to February1993.

Data Collection and Analysis

Data collection was carried out from Monday toFriday each working week in a specially equippedclassroom in each of the three schools chosen. Thesingle procedure, lasting 24 hr, was on day 1 (Mon-day, Tuesday, Wednesday, or Thursday, around 9:00AM) two urine specimen jars were given to each stu-dent, one for his/her urine and one for urine of his/her mother. On the next day (Tuesday, Wednesday,Thursday, or Friday, respectively), each subject re-turned, at the same hour, the two urine specimensand was asked to fill out a questionnaire. In thisway, the sampling procedure did not include the pe-riod covered by the weekend but, correctly, allowedhomogeneous and transversal comparison of thedata inside the selected population.

Questionnaire. Ninety questions were addressedto all the subjects by one interviewer. They re-sponded to individual, familiar, and environmentalitems. The questionnaire was readministered to 80subjects after 1 month by the same interviewer. Thedouble answers showed a K (index of Cohen) ofaround 0.93.

Urine sample. The specimen jars were filled withthe first urine of the morning, the second day of theprocedure. Methodology of cotinine analysis andquality control is published elsewhere (Bono, 1994,1996). Urinary cotinine was quantified by compari-son to a curve obtained by standard additions of co-tinine to urine of a nonsmoker treated in the same

way. The detection limit was below 1 ng/ml and re-covery was 100%.

Weight and Height

The body mass index (B.M.I.)—weight/height2—has been calculated with the aim of considering thisindividual condition as a possible confounding factorinvolved in the composition of the epidemiologicalsample.

Statistical Analysis

Statistical analyses were carried out using theSpearmann and Wilcoxon nonparametric tests forabnormally distributed data. All analyses were per-formed with S.A.S. Packages (SAS 1992).

RESULTS

Table 1 describes numerically the two populationsconsidered, in particular, the students were ana-lyzed considering sex, age, and body mass indexes.The homogeneous age distribution and B.M.I. of stu-dents allowed consideration of these two parametersas not influencing the results obtained. Table 2shows a general description of urinary cotinine forboth the two groups considering means, standarddeviations, median, and the interquartile differ-ences.

Table 3 describes mean and median relative tourinary cotinine values, considering active and pas-sive smoking status of the 333 students. A priori,student nonactive smokers were broken down into

TABLE 1General Description of the Epidemiological Sample

Students

Totalstudents Male Female Mothers

No. 333 95 238 293Age 15.88 ± 0.6 — — 43.380 ± 6.5B.M.I. 20.30 20.27 20.31 —

Note. B.M.I., body mass index.

TABLE 2General Description of Cotinine Measured in the Two

Populations Considered

No.

Urinary cotinine

Mean(ng/mL)

S.D.(ng/mL)

Median(ng/mL)

Q3–Q1(ng/mL)

Students 333 87.02 202.11 33.40 38.38Mothers 293 268.78 499.27 30.28 253.67

BONO ET AL.96

four categories according to smoking habits of peoplesharing the household: (a) none of them smoked: nosmokers, (b) at least one member of the family (in-cluding the father, but not the mother) smoked: pas-sive to other cohabitants, (c) only the mothersmoked: passive to mother, and (d) the mother andat least one other member of the family smoked:passive to mother and others. The Wilcoxon test,applied to the three main group of exposure, showeda high statistical significance (P 4 0.0001).

Table 4 shows the same observation but relative tothe 293 mothers. The Wilcoxon test, applied to thethree main groups (active, passive to husband, and

nonsmokers), showed a high statistical significance(P 4 0.0001).

Table 5 describes the relationships between uri-nary cotinine in the two populations and exposure totobacco smoke. Students and mothers (a and b) showpositive and statistically significant correlations be-tween the number of cigarettes smoked and theirurinary cotinine.

The degree of exposure to ETS of students is alsopartially demonstrated by significative correlationsbetween urinary cotinine and total number of ciga-rettes smoked at home (h), cigarettes smoked bymothers (e), cigarettes smoked by fathers (f), andother cohabitants (g). Instead, the degree of expo-sure to ETS of mothers is partially demonstrated bypositive and statistically significant correlations be-tween urinary cotinine and the total number of ciga-

TABLE 3Mean and Median of the 333 Students Considering the

Tobacco Smoke Exposure Status

Exposurestatus No.

Mean(S.D.)

(ng/mL)Median(ng/mL)

Q3–Q1(ng/mL)

Active smokers 61 299.08 (385.18) 128.85 290.37Passive smokers 163 46.59 (86.19) 33.4 27.13

Passive to motherand others 64 57.67 (122.0) 34.85 33.7

Passive to mother 27 39.62 (18.56) 40.0 17.57Passive to other

cohabitants 72 39.35 (58.59) 27.5 26.05No smokers

(active or passive) 109 28.81 (26.92) 20.38 25.57

Note. The Wilcoxon test was applied for median trend and theP obtained was 0.0001.

TABLE 4Mean and Median of the 293 Mothers Considering the

Tobacco Smoke Exposure Status

Exposurestatus No.

Mean(S.D.)

(ng/mL)Median(ng/mL)

Q3–Q1(ng/mL)

Active smokers 100 733.06 (632.3) 626.39 773.33Passive to husband 72 33.57 (64.06) 17.62 26.35Passive to others or

not passively exposed 121 25.02 (39.16) 16.54 19.56

Note. The Wilcoxon test was applied for median trend and ‘‘p’’obtained was 0.0001.

TABLE 5Spearmann Correlation Analysis between Urinary Cotinine in the Two Populations and Some

Environmental Parameters

Urinary cotinine

Students Mothers

(a) Cig./die smokedby the student r 4 0.52304, P 4 0.0001

(b) Cig./die smokedby mother r 4 0.79160, P 4 0.0001

(c) Urinary cotinineof students — r 4 0.25368, P 4 0.0001

(d) Cig./die smokedby the student — N.S.

(e) Cig./die smokedby mother r 4 0.25209, P 4 0.0001 —

(f) Cig./die smokedby father/husband r 4 0.17817, P 4 0.0011 r 4 020530, P 4 0.0004

(g) Cig./ die smokedby others r 4 0.13931, P 4 0.0109 N.S.

(h) Cig./m2 ofthe apartment r 4 0.32867, P 4 0.0001 r 4 0.45617, P 4 0.0001

Note. a, b, and c, ng/mL; cig., number of cigarettes smoked.

TOBACCO EXPOSURE IN ADOLESCENTS: ROLE OF COHABITANTS 97

rettes smoked at home (h) and the number of ciga-rettes smoked by their husbands (f). Furthermore, arelationship between urinary cotinine of studentsand their mothers is observed (c). No other types oftobacco (pipe, cigars) were consumed in the familiesconsidered.

Table 6 shows the possible correlations consider-ing only the students who actively smoke and theirparents. Students smokers show levels of urinarycotinine and number of cigarettes actively smokedthat correlated significantly to the number of ciga-rettes smoked by their fathers but not by their moth-ers. These findings can partially demonstrate thatthe start of the smoking activity of students can de-pend principally by the spirit of emulation of thefather.

DISCUSSION AND CONCLUSIONS

Data shown in this work identifies a direct rela-tionship between the levels of exposure to tobaccosmoke described by a questionnaire and urinary co-tinine. This relationship was proved by the statisti-cally demonstrated difference between concentra-tions of cotinine in urine of smokers and nonsmokersand, above all, by the difference inside the passivesmoker groups selected using the questionnaire.

The present epidemiological sample represents aparticular group of people (16-year-old students)having a life style still strictly bound to the homeenvironment and, therefore, to the smoking habit oftheir parents. In fact, the non-active smokers (Table3) show urinary cotinine levels described by the fol-lowing means: 28.81, 39.35, 39.62, and 57.67 ng/mL.This finding demonstrates a trend of exposure fromno exposure to a maximum level of passive exposure(mothers + fathers + other cohabitants). Similar re-

sults can be observed considering the urinary coti-nine of mothers (Table 4).

Cotinine trend observed in Table 3 is confirmed bythe r of correlation showed in Table 5 (e, f, and g). Infact, the r of Spearman decreases considering thesmoking habits of the mother, the father, and theother cohabitants: 0.252 > 0.178 > 0.139. These re-sults could depend on the different amounts of timespent at home by the students together with theirparents or other cohabitants. Excluding the expo-sure at home, no other exposures to ETS during the24 hr preceding the urine sampling seems to con-tribute significatively to the passive exposure of thenonactive smokers. Data from questionnaires ex-plained that these 272 students spent their after-noon, evening, and night at home; 20.8% of themspent, on average, also 2 hr during the afternoonmaking sportive activities or shopping and 3.1%went after dinner to the cinema, where smoking isprohibited. At home, each cohabitant or visitor whosmoked was included in the group named ‘‘other co-habitants.’’

Finally, the active smoking habit potentially ac-quired by the adolescents could be induced also bythe smoking habits of the fathers. This is demon-strated by the light positive and statistically signifi-cative correlation between cotinine of studentssmokers or number of cigarettes smoked by the stu-dents and the number of cigarettes smoked by thefathers.

The present findings could be helpful in cancerresearch and in a prevention campaign against to-bacco smoke in an age class in which respiratorysensitivity is very high and the use of tobacco canstart.

ACKNOWLEDGEMENTS

This study was made possible by a grant of from AssociazioneItaliana per la Ricerca Sul Cancro (1993) and from Ministerodell’Universita, della Ricerca Scientifica e Tecnologica, quota60%, es. fin. 1994 and 1995.

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TABLE 6Spearmann Correlation Analysis between Urinary Coti-

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Number of cigarettes activelysmoked vs cigarettes smokedby mother r 4 0.24778 P 4 0.0542

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