Physiological Daily Inhalation Rates for Free-Living Individuals Aged 1 Month to 96 Years, Using Data from Doubly Labeled Water Measurements: A Proposal for Air Quality Criteria, Standard Calculations and Health Risk Assessment

ABSTRACT Reported disappearance rates of oral doses of doubly labeled water (2H2O and H2 18O) in urine, monitored by gas-isotope-ratio mass spectrometry for an aggregate period of over 30,000 days and completed with indirect calorimetry and nutritional balance measurements, have been used to determine physiological daily inhalation rates for 2210 individuals aged 3 weeks to 96 years. Rates in m3/kg-day for healthy normal-weight individuals (n = 1252) were higher by 6 to 21% compared to their overweight/obese counterparts (n = 679). Rates for healthy normal-weight males and females drop by about 66 to 75% within the course of a lifetime. Infants and children between the age of 3 weeks to less than 7 years inhale 1.6 to 4.3 times more air (0.395 ± 0.048 to 0.739 ± 0.071 m3/kg-day, mean ± S.D., n = 581) than adults aged 23 to 96 years (0.172 ± 0.037 to 0.247 ± 0.039 m3/kg-day, n = 388). The 99th percentile rate of 0.725 m3/kg-day based on measurements for boys aged 2.6 to less than 6 months is recommended for air quality criteria and standard calculation for non-carcinogenic compounds pertaining to individuals of any age or gender (normality confirmed using the Shapiro-Wilk test, p ≥ 0.05). This rate is 2.5-fold more protective than the daily inhalation estimate of 0.286 m3/kg-day published by the Federal Register in 1980 (i.e., 20 m3/day for a 70-kg adult). It ensures that very few newborns aged 1 month and younger, less than 1% of infants aged 2.6 to less than 6 months and of course no older individuals up to 96 years of age inhale more toxic chemicals than associated safe doses which are not anticipated to result in any adverse effects in humans, when air concentration reaches the resulting air quality criteria and standard values. This rate is also protective for underweight, overweight, and obese individuals. Finally, as far as newborns are concerned, a rate of 0.956 m3/kg-day based on the 99th percentile estimates is recommended for short-term criteria and standard calculations for toxic chemicals that yield adverse effects over instantaneous to short-term duration. Key Words: daily inhalation ratesdistribution percentilesprobability density functionsair quality criteriastandard valuerisk assessmentdoubly labeled water. ACKNOWLEDGMENTS The authors thank Mrs. Isabelle Brochu for the linguistic revision of the present article. They also wish to point out that the views expressed in this article may not reflect the official policy of the Québec Ministry of Sustainable Development, Environment and Parks. Web tables for this article can be viewed by accessing the publisher's website. Notes a Formula-fed infants. b Breast-fed infants. c Healthy infants with very low birth weight (CitationReichman et al. 1981, Citation1982). d Infants evaluated as being clinically healthy and neither underweight nor overweight (CitationButte et al. 1990). e Total daily energy requirements (TDERs) reported in Table Web-2 were converted into physiological daily inhalation rates by the following equation: TDER*H*(VE/VO2)*10− 3. H = 0.21 L of O2/Kcal and VE/VO2 = 27 (CitationLayton 1993). TDER = total daily energy requirement. TDER = (TDEE + ECG). TDEE = total daily energy expenditure. ECG = stored daily energy cost for growth. ECGs from Table Web-1 were initially added to the basic TDEEs in order to obtain the appropriate TDERs (Table Web-2). f TDEEs based on nutritional balance measurements (intake and output analysis) during 3-day periods for each infant. g TDEEs based on 2H2O and H2 18O disappearance rates from urine monitored by gaz-isotope-ratio mass spectrometry during 14-day periods. h Daily metabolic equivalent or daily BEE multiplier (TDER/BEE). BEEs or basal energy expenditures (BMRs expressed on a 24-hour basis) were measured by indirect calorimetry (CitationButte et al. 1990; CitationReichman et al. 1981, Citation1982). a Measured body weight. Normal-weight individuals defined according to the body mass index (BMI) cut-offs. BMIs for sub-groups are reported in Table Web-4. b Observed p values based on Shapiro-Wilk normality tests. Daily metabolic equivalent values are given in Table 8. c Total daily energy requirements (TDERs) reported in Table Web-4 (in kcal/day) were converted into physiological daily inhalation rates by the following equation: TDER*H*(VE/VO2)*10−3. H = 0.21 L of O2/Kcal and VE/VO2 = 27 (CitationLayton 1993). TDER = (TDEE + ECG). TDEE = total daily energy expenditure. ECG = stored daily energy cost for growth. d Percentiles based on a normal distribution assumption for all age groups. a Measured body weight. Normal-weight and overweight/obese males defined according to the body mass index (BMI) cut-offs. BMIs for sub-groups are reported in Table Web-6. b Observed p values based on Shapiro-Wilk normality tests. Daily metabolic equivalent values are given in Table 9. c Total daily energy requirements (TDERs) reported in Table Web-6 (in kcal/day) were converted into physiological daily inhalation rates by the following equation: TDER*H*(VE/VO2)*10− 3. H = 0.21 L of O2/Kcal and VE/VO2 = 27 (CitationLayton 1993). TDER = (TDEE + ECG). TDEE = total daily energy expenditure (Table Web-5). d Percentiles based on a normal distribution assumption for all age groups. n = number of individuals; S.D. = standard deviation. a Measured body weight. Normal-weight and overweight/obese females defined according to the body mass index (BMI) cut-offs. BMIs for sub-groups are reported in Table Web-8. b Observed p values based on Shapiro-Wilk normality tests. Daily metabolic equivalent values are given in Table 10. c Total daily energy requirements (TDERs) reported in Table Web-8 (in kcal/day) were converted into physiological daily inhalation rates by the following equation: TDER*H*(VE/VO2)*10− 3. H = 0.21 L of O2/Kcal and VE/VO2 = 27 (CitationLayton 1993). TDER = (TDEE + ECG). TDEE = total daily energy expenditure (Table Web-7). d Percentiles based on a normal distribution assumption for all age groups. n = number of individuals; S.D. = standard deviation. a Thin Chilean laborers. b Gambian laborers. c Guatemalan mothers. d Gambian farmers. e Measured body weight. f Total daily energy requirements (TDERs) were converted into physiological daily inhalation rates by the following equation: TDER*H*(VE/VO2)*10− 3. H = 0.21 L of O2/Kcal and VE/VO2 = 27 (CitationLayton 1993). TDER = (TDEE + ECG). g Daily metabolic equivalent or daily BEE multiplier (TDER/BEE). BEEs or basal energy expenditures (BMRs expressed on a 24-hour basis) were measured by indirect calorimetry (CitationBlack et al. 1996). a Measured body weight. b Total daily energy requirements (TDERs) were converted into physiological daily inhalation rates by the following equation: TDER*H*(VE/VO2)*10− 3. H = 0.21 L of O2/Kcal and VE/VO2 = 27 (CitationLayton 1993). TDER = (TDEE + ECG). c Daily metabolic equivalent or daily BEE multiplier (TDER/BEE). BEEs or basal energy expenditures (BMRs expressed on a 24-hour basis) were measured by indirect calorimetry (CitationBlack et al. 1996). a Over the 21 days of the Tour de France. b On Mount Everest. c In the first 20 days of sled hauling across the Arctic by adults aged 35.3 and 41 years. d Measured body weight. e Total daily energy requirements (TDERs) were converted into physiological daily inhalation rates by the following equation: TDER*H*(VE/VO2)*10− 3. H = 0.21 L of O2/Kcal and VE/VO2 = 27 (CitationLayton 1993). TDER = (TDEE + ECG). f Daily metabolic equivalent or daily BEE multiplier (TDER/BEE). BEEs or basal energy expenditures (BMRs expressed on a 24-hour basis) were measured by indirect calorimetry (CitationBlack et al. 1996). a Observed p values based on Shapiro-Wilk normality tests. The number of individuals and measured body weights were gathered according to body mass index cut-offs and are given in Table 2. b Total daily energy requirements (TDERs) reported in Table Web-4 (in kcal/kg-day) were converted into physiological daily inhalation rates by the following equation: TDER*H*(VE/VO2)*10−3. H = 0.21 L of O2/Kcal and VE/VO2 = 27 (CitationLayton 1993). TDER = (TDEE + ECG). TDEE = total daily energy expenditure. ECG = stored daily energy cost for growth. TDEEs in Table Web-3 were based on 2H2O and H2 18O disappearance rates from urine monitored by gaz-isotope-ratio mass spectrometry during 7- to 21-day periods for 1,252 individuals aged 2.6 months to 96 years (CitationIOM 2002). ECGs from Table Web-1 were initially added to the basic TDEEs in order to obtain the appropriate TDERs. c Percentiles based on a normal distribution assumption for all age groups. d Daily metabolic equivalent or daily BEE multiplier (TDER/BEE). BEEs or basal energy expenditures (BMRs expressed on a 24-hour basis) were measured by indirect calorimetry (Table Web-3; CitationIOM 2002). S.D. = standard deviation. a Observed p values based on Shapiro-Wilk normality tests. The number of individuals and measured body weight for normal-weight and overweight/obese males were gathered according to body mass index (BMI) cut-offs and are given in Table 3. BMIs for sub-groups are reported in Table Web-6. b Total daily energy requirements (TDERs) reported in Table Web-6 (in kcal/kg-day) were converted into physiological daily inhalation rates by the following equation: TDER*H*(VE/VO2)*10− 3. H = 0.21 L of O2/Kcal and VE/VO2 = 27 (CitationLayton 1993). TDER = (TDEE + ECG). TDEE = total daily energy expenditure (Table Web-5). c Percentiles based on a normal distribution assumption for all age groups. d Daily metabolic equivalent or daily BEE multiplier (TDER/BEE). BEEs or basal energy expenditures (BMRs expressed on a 24-hour basis) were measured by indirect calorimetry (Table Web-5; CitationIOM 2002). a Observed p values based on Shapiro-Wilk normality tests. The number of individuals and measured body weight for normal-weight and overweight/obese females were gathered according to body mass index (BMI) cut-offs and are given in Table 4. BMIs for sub-groups are reported in Table Web-8. b Total daily energy requirements (TDERs) reported in Table Web-8 (in kcal/kg-day) were converted into physiological daily inhalation rates by the following equation: TDER*H*(VE/VO2)*10− 3. H = 0.21 L of O2/Kcal and VE/VO2 = 27 (CitationLayton 1993). TDER = (TDEE + ECG). TDEE = total daily energy expenditure (Table Web-7). c Percentiles based on a normal distribution assumption for all age groups. d Daily metabolic equivalent or daily BEE multiplier (TDER/BEE). BEEs or basal energy expenditures (BMRs expressed on a 24-hour basis) were measured by indirect calorimetry (Table Web-7; CitationIOM 2002).