Results of the Canadian Health Measures Survey Cycle 1 (2007-2009)
Cat. No.: H128-1/10-601E
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Table of Contents
8.1.13 Zinc (CASRN 7440-66-6)
Zinc was measured in the blood and urine of all participants aged 6-79 years in the Canadian Health Measures Survey and is presented as mg/L in blood and as both µg/L and µg/g creatinine in urine (Tables 8.1.13a, 8.1.13b, 8.1.13c). Finding a measurable amount of zinc in blood or urine is an indicator of exposure to zinc and does not necessarily mean that an adverse health effect will occur. Since it is an essential nutrient, its presence is expected. These data provide reference ranges for blood and urinary levels of zinc in the Canadian population.
Zinc - Arithmetic and geometric means, and selected percentiles of blood concentrations (mg/L) for the Canadian population aged 6-79 years, Canadian Health Measures Survey Cycle 1, 2007-2009.
8.8.2 cis-3-(2,2-Dibromovinyl)-2,2-Dimethylcyclopropane-1-Carboxylic Acid (cis-DBCA)
Appendix B - Limits of Detection for the Environmental Chemicals Measured in the CHMS
Metals and Trace Elements in Urine
Mercury, inorganic 0.20 µg/L
Aroclor 1260* 0.1 µg/L
The development and implementation of the biomonitoring component of the Canadian Health Measures Survey was achieved through extensive contributions of programs and staff across Health Canada and Statistics Canada. A special thank you goes out to the participants of the survey, without whom this study would not be possible.
The Report on Human Biomonitoring of Environmental Chemicals in Canada presents national baseline data on concentrations of environmental chemicals in Canadians. These data were collected as part of Cycle 1 of the Canadian Health Measures Survey (CHMS), the most comprehensive national direct health-measures survey conducted in Canada to date. Statistics Canada, in partnership with Health Canada and the Public Health Agency of Canada, launched the CHMS to collect health and wellness data and biological specimens on a nationally representative sample of Canadians. Data were collected between March 2007 and February 2009 from approximately 5,600 Canadians aged 6-79 years at 15 sites across Canada, from Moncton to Vancouver. Collection for the second cycle of the CHMS began in September 2009 and includes children as young as 3 years of age. Cycle 2 will be completed in 2011, while planning for future cycles is underway.
The CHMS biomonitoring component, the first study of its kind in Canada, measured environmental chemicals and/or their metabolites, in blood and urine of survey participants. For the purposes of this report, an environmental chemical is defined as a chemical substance, either man-made or natural, that is present in the environment and to which humans may be exposed through media such as air, water, food, soil, dust, or consumer products.
In this report, the general CHMS survey design and implementation are described, with emphasis on the biomonitoring component. This is followed by descriptive summaries for each chemical, outlining the chemical's identity, common uses, occurrence in the environment, potential sources of exposure in the human population, toxicokinetics in the body, and health effects. Finally, data tables specific to each chemical are provided, with descriptive statistics on the distribution of blood and/or urine concentrations in the sample population.
The primary purpose of the Report on Human Biomonitoring of Environmental Chemicals in Canada is to provide human biomonitoring data to scientists, and health and environment officials, to aid in assessing the exposure to environmental chemicals and assessing policies to reduce exposure to chemicals for the protection of the health of Canadians.
Some specific uses of the information presented in this report include the following:
The CHMS was designed as a cross-sectional survey to address important data gaps and limitations in existing health information in Canada. Its principal objective is to collect national-level baseline and reference ranges on important indicators of Canadians' health status, including those pertaining to exposures to environmental chemicals. This information is important in understanding health risk factors, detecting emerging trends in risk factors and exposures, advancing health surveillance and research, and assessing the effectiveness of actions by government and others in Canada. Detailed descriptions of the CHMS rationale, survey design, sampling strategy, clinic operations and logistics, and ethical, legal and social issues, have previously been published (Tremblay et al., 2007; Giroux, 2007; Day et al., 2007; Bryan et al., 2007; Statistics Canada, 2010).
The CHMS targets the population aged 6 to 79 years living at home and residing in the ten provinces and three territories. People living on reserves or in other Aboriginal settlements in the provinces, residents of institutions, full-time members of the Canadian Forces, persons living in certain remote areas, and persons living in areas with a low population density were excluded.
To meet the objective of producing reliable estimates at the national level by age group and sex, the CHMS required a sample of at least 5000 persons equally distributed among five age groups (6-11, 12-19, 20-39, 40-59, and 60-79 years) and sex, for a total of ten groups.
To meet the requirements of the CHMS, a multistage sampling strategy was used.
The CHMS required participants to report to a mobile examination centre (MEC) and be able to travel to that clinic within a reasonable period of time. The Canadian Labour Force Survey (LFS) sampling frame was used to create 257 collection sites across the country. A collection site is a geographic area with a population of at least 10,000 and a maximum respondent travel distance of 100 kilometres (50 kilometres in urban areas and 100 kilometres in rural areas). Areas not meeting these criteria were excluded. Nonetheless, the CHMS covers 96.3% of the Canadian population aged 6 to 79 (Statistics Canada, 2010).
A large number of collection sites with few respondents would have optimized the precision of the estimates. However, the logistical and cost constraints associated with the use of mobile examination centres restricted the number of collection sites to 15. The 15 collection sites were selected from within the five standard regional boundaries used by Statistics Canada (Atlantic, Quebec, Ontario, Prairies [including Yellowknife], and British Columbia [including Whitehorse]) and were allocated to these regions in proportion to the size of the population. While not every province and territory in Canada had a collection site, the CHMS sites were chosen to represent the Canadian population, East to West, including larger and smaller population densities. The collection sites selected for Cycle 1 of the CHMS are listed in Table 1 (Statistics Canada, 2010).
The 2006 Canadian Census was used as the frame to select dwellings. Within each site, dwellings with known household composition at the time of the 2006 Census were stratified by age of household residents at the time of the survey, with the five age-group strata corresponding to the CHMS age groups (6-11, 12-19, 20-39, 40-59, 60-79). Within each site, a simple random sample of dwellings was selected in each stratum. Each selected dwelling was then contacted and asked to provide a list of current household members, and this list was used to select the survey respondents. One or two people were selected, depending on the household composition.
The environmental chemicals selected for inclusion in the CHMS were based on the results of an expert workshop on Human Biomonitoring of Environmental Chemicals hosted by Health Canada in 2003 and on subsequent consultations with various Health Canada programs and Statistics Canada. The expert workshop had representation from the Canadian government, academia, public health agencies, public health and medical laboratories, and the US Centers for Disease Control and Prevention. Substances were selected from an initial candidate list of over 220 individual chemicals and/or groups of environmental chemicals. Selection was based on health risks, evidence of human exposure, existing data gaps, obligations under national and international treaties, conventions and agreements, availability of standard laboratory analytical methods, and current and anticipated health policy development and implementations.
The environmental chemicals selected for biomonitoring in the Canadian Health Measures Survey were chosen based on one or more of the following criteria:
Ultimately the list was narrowed by the volume of biospecimen available from survey participants to conduct the analysis. Blood volume is generally limited, thus the number of environmental chemicals measured in blood is less than that analyzed in urine. In addition, blood collected was also required for analysis of chronic and infectious diseases and nutritional biomarkers. Some analytes were measured because the analytical method used, such as the ICP-MS method for the metal panel, provided results for additional chemicals with little or no additional biospecimen volume and cost, including essential nutrients such as copper, molybdenum, selenium, and zinc, which are required for maintenance of good health. A full list of the chemicals measured in CHMS 2007-2009 is presented in Table 2.
Chemicals Measured in the Canadian Health Measures Survey 2007-2009
Metals and Trace Elements
Polybrominated Flame Retardants
Organophosphate Insecticides (Metabolites)
Pyrethroid Insecticides (Metabolites)
Phthalates (Metabolites)Footnote *
Due to the high cost of laboratory analysis, some environmental chemicals were measured in subsamples from the CHMS respondents. Subsamples for specific environmental chemicals were independently selected, and as such, a specific respondent could have been selected for measurement of one, two, or all of the environmental chemicals. Consequently, the age range for which a chemical was measured varied by chemical (Table 3). A collocated sampling method was used to minimize the selection of two people living in the same household (6-11 year olds and other age groups) for the same environmental chemical measurement in order to maximize the representativeness of the population sample (Giroux, 2007). Further details on the subsampling for environmental chemicals are available in the Canadian Health Measures Survey (CHMS) Data User Guide: Cycle 1 (Statistics Canada, 2010).
|Measure||Matrix||Target Sample Size||Age (years)|
|Metals and trace elements||Urine and Blood||5600||Yes||Yes||Yes||Yes||Yes|
|Polychlorinated biphenyls (PCBs)||Plasma||1500||No||No||Yes||Yes||Yes|
|Polybrominated flame retardants (PBB & PBDEs)||Plasma||1500||No||No||Yes||Yes||Yes|
|Perfluorinated compounds (PFCs)||Plasma||1500||No||No||Yes||Yes||Yes|
Personal information collected through the CHMS is protected under the federal Statistics Act. Under this Act, Statistics Canada is obliged to safeguard and to keep in trust the information it obtains from the Canadian public. Consequently, Statistics Canada has established a comprehensive framework of policies, procedures, and practices to protect confidential information against loss, theft, unauthorized access, disclosure, copying, or use, which includes physical, organizational, and technological measures. The steps taken by Statistics Canada to safeguard the information collected in the CHMS have been described previously by Day et al. (2007).
Ethics approval for all components of the CHMS was obtained from Health Canada's Research Ethics Board. Informed written consent for the clinic portion of the CHMS was obtained from respondents older than 14 years of age. For younger children, a parent or legal guardian provided written consent and the child provided written assent. Participation in this survey was voluntary and respondents could opt out of any part of the survey at any time.
A strategy was developed to communicate results to survey respondents with the advice and expert opinion of the CHMS Laboratory Advisory Committee, the Physician Advisory Committee, and Health Canada's Research Ethics Board (Day et al., 2007). For the environmental chemicals, only results for lead, mercury, and cadmium were actively reported to respondents. However, respondents could receive all other test results upon request to Statistics Canada. More information on reporting to respondents can be found in Haines et al. (2010).
Fieldwork for the CHMS took place over two years from March 2007 to February 2009. Data were collected sequentially at 15 sites across Canada. The sites were ordered to take into account seasonality by region and the temporal effect, subject to operational and logistical constraints. The temporal effect means that the number of sites by region were distributed evenly in year one and year two, with the exception of the Atlantic region, which had only one site (Giroux, 2007).
Respondents were contacted by Statistics Canada through an advance letter and brochure mailed to the household informing them they would be contacted to participate in the survey.
Data collection included a combination of a household personal interview using a computer-assisted interviewing method and for the physical measures, a clinic visit to a Mobile Examination Centre (MEC) specifically designed for the survey. The field team consisted of household interviewers and the CHMS MEC staff, including trained health professionals who performed the physical measures testing. Respondents were first administered a household questionnaire in their home by an interviewer and, within approximately two weeks, the respondents visited an MEC where trained health professionals took the physical health measurements and collected the blood and urine specimens. Biospecimens were processed and stored prior to shipment to the CHMS laboratories.
When visiting the home, the interviewer randomly selected one or two respondents and conducted separate 45 to 60 minute health interviews. This interview collected demographic and socioeconomic data and information about lifestyle, medical history, current health status, the environment, and housing conditions.
Each MEC consisted of two trailers linked by an enclosed pedestrian walkway. One trailer served as a reception and administration area, while the other contained clinic rooms and a laboratory. At the MEC, health professionals took the respondents' physical measurements, such as height, weight, blood pressure, lung function, and physical fitness, and collected their blood and urine specimens.
The MEC operated seven days a week in order to complete approximately 350 clinic visits at each site over six to eight weeks and to accommodate respondents' schedules. Clinic appointments averaged about 2.5 hours. Children under 14 years of age were accompanied by a parent or legal guardian. To maximize response rates, respondents who were unable or unwilling to go to the clinic were offered the option of a home visit to perform the physical measures portion of the survey.
At the start of the clinic visit, respondents signed the consent/assent forms prior to any testing and immediately thereafter provided a urine sample. For logistical purposes, spot samples were collected rather than 24-hour urine samples. Urine samples were collected in 120-mL urine specimen containers.
The respondents were administered a series of screening questions to determine the respondents' eligibility for the various tests, including phlebotomy (i.e., blood collection), based on pre-existing exclusion criteria. Blood specimens were drawn by a certified phlebotomist and the amount of blood drawn was dependent upon the age of the respondent. For children aged 6 to 11 years, approximately 28 mL was drawn; for 12 to 13 years, 38 mL; for 14 to 19 years, 45 mL; and for 20 to 79 years, 75 mL.
All blood and urine specimens collected in the MEC were processed in the MEC, including aliquoting and centrifuging of serum and plasma. Two -20ºC freezers were used to temporarily store the biospecimens until shipping. Once a week, the specimens were shipped to the reference laboratory for analysis. Standardized operating procedures (SOPs) were developed for the collection of blood and urine specimens, processing and aliquoting procedures as well as for shipping biospecimens to ensure adequate quality of the data and to standardize data collection. A priority sequence for laboratory analysis was established in the event that an insufficient volume of biospecimen was collected for complete analysis of the environmental chemicals, as well as for analysis of infectious diseases, nutritional status, diabetes, and cardiovascular disease risk factors. Details on the reference laboratory, collection tubes, aliquot volumes, temporary storage and shipping require-ments, and priority testing are presented in Table 4.
|Measure||Matrix||Reference LaboratoryTable 1 footnote a||Collection Tube (size and typeTable 1 footnote b)||Aliquot VolumeTable 1 footnote c||StorageTable 1 footnote d/Shipping|
Table 1 footnotes
|Lipids: triglycerides & total cholesterol||Serum||HC||8.5 mL Red/Grey SST||1.0 mL||freezer/dry ice|
|Metals and trace elements & inorganic mercury||Whole Blood||INSPQ||6.0 mL Lavender EDTA||1.8 mL||freezer/ice pack|
|PCBs, organochlorines, PBB & PBDEs||Plasma||INSPQ||10.0 mL Lavender EDTA||2.7 mL||freezer/ice pack|
|Perfluorinated compounds||Plasma||INSPQ||10.0 mL Lavender EDTA||1.8 mL||freezer/dry ice|
|Creatinine & cotinine||Urine||INSPQ||Urine specimen container||4.5 mL||freezer/dry ice|
|Metals and trace elements & inorganic mercury||Urine||INSPQ||Urine specimen container||4.5 mL||freezer/dry ice|
|Bisphenol A, organophosphate insecticides, pyrethroid insecticides, phenoxy herbicide & chlorophenol||Urine||INSPQ||Urine specimen container||20.0 mL||freezer/ice pack|
To maximize the reliability and validity of the data and to reduce systematic bias, the CHMS developed quality assurance and quality control protocols for all aspects of the fieldwork. Quality assurance for the clinic covered staff selection and training, instructions to respondents (pre-testing guidelines) and issues related to data collection. All staff had appropriate education and training for their respective positions. To ensure consistency among measurement techniques, procedures manuals and training guides were developed in consultation with, and reviewed by, experts in the field. Quality control samples at each site consisted of one field blank (bovine serum for the perfluorinated chemicals and de-ionized water for all analytes) and blind commercial control samples for arsenic, cadmium, lead and mercury in whole blood. These quality control samples were sent to the reference laboratory with a regular specimen shipment. Results were sent to Statistics Canada's CHMS headquarters, along with all other respondent results, where they were assessed to determine the accuracy of the methodology based on the defined analyte concentration. If required, feedback was provided quickly to the reference laboratory for review and remedial action. During this quality assurance process, it was determined that the vacutainers used in the blood metal analysis were contaminated with manganese and a correction factor of 14 nmol/L was applied to all blood manganese results to account for this contamination.
Detailed descriptions of the CHMS clinic operations and logistics have been described previously in Bryan et al., (2007) and Giroux (2007), and are presented in the Canadian Health Measures Survey (CHMS) Data User Guide: Cycle 1 (Statistics Canada, 2010).
Laboratory analysis of environmental chemicals and creatinine was performed at the Centre de toxicologie du Québec (CTQ) of L'Institut national de santé publique du Québec (INSPQ), Québec City. INSPQ followed standardized operating procedures that were developed for every assay and technique performed in their laboratory. The laboratory, which is accredited under ISO 17025, uses numerous internal and external quality control programs. Laboratory analysis of serum lipids was performed at the Health Canada laboratories, Bureau of Nutritional Sciences, Nutrition Research Division, Ottawa. This lab also uses numerous internal and external quality control programs and is a member of a proficiency testing program. The limit of detection (LOD) for each method is presented in Appendix B.
Internal quality control measures within INSPQ include the use of calibration standards, laboratory blanks and other in-house reference materials. External quality control measures include participation in inter-laboratory comparison studies for most analytes. Quality assurance reviews were conducted on laboratory data for each site, in order to identify inconsistencies in results, such as assay drifting. In particular, it was determined during regular quality control testing that the vacutainers used in the blood metal analysis were contaminated with manganese. A correction factor of 14 nmol/L was applied to all blood manganese results.
The methods used in the analysis of the environmental chemicals, creatinine, and lipids are described below.
Blood samples were diluted in a basic solution containing octylphenol ethoxylate and ammonia. They were analyzed for total arsenic, cadmium, copper, lead, manganese, total mercury, molybdenum, nickel, selenium, uranium, and zinc by inductively coupled plasma mass spectrometry (ICP-MS), Perkin Elmer Sciex, Elan DRC II (M-572). Matrix matched calibration was performed using blood from a non-exposed individual (INSPQ, 2009a).
Blood was digested in a water bath at 80°C with an equal volume of concentrated nitric acid. Inorganic mercury was analyzed by cold vapour atomic absorption spectrometry using a mercury monitor (Model 100 from Pharmacia). An aliquot of the digest was then introduced in the system's reaction chamber containing a reducing solution of stannous chloride. The mercury vapour was generated and detected. Aqueous calibration was performed (INSPQ, 2009b).
Urine samples were diluted in dilute nitric acid (0.5%) and analyzed for antimony, total arsenic, cadmium, copper, lead, manganese, molybdenum, nickel, selenium, uranium, vanadium, and zinc by ICP-MS, Elan DRC II (M-571). Matrix matched calibration was performed using urine from non-exposed individuals (INSPQ, 2009c).
Following an acid mineralization, the resulting solution was diluted and analyzed on the Flow Injection Mercury System (FIMS) module from Perkin Elmer (M-568) using cold vapour atomic absorption spectrometry. Ionized mercury was reduced to metallic mercury by the action of tin chloride. The volatile mercury formed was detected in the UV/VIS range (INSPQ, 2009d).
Plasma samples were enriched with internal standards and denatured with formic acid. Organohalogenated compounds, including PCB 28, PCB 52, PCB 66, PCB 74, PCB 99, PCB 101, PCB 105, PCB 118, PCB 128, PCB 138, PCB 146, PCB 153, PCB 156, PCB 163, PCB 167, PCB 170, PCB 178, PCB 180, PCB 183, PCB 187, PCB 194, PCB 201, PCB 203, PCB 206, aldrin, α-chlordane, γ-chlordane, cis-nonachlor, trans-nonachlor, oxychlordane, β-HCH, γ-HCH, p,p'-DDE, p,p'-DDT, hexachlorobenzene, mirex, toxaphene parlar 26, toxaphene parlar 50, PBB 153, PBDE 15, PBDE 17, PBDE 25, PBDE 28, PBDE 33, PBDE 47, PBDE 99, PBDE 100, and PBDE 153, were automatically extracted from the aqueous matrix using solid phase separation. Extracts were cleaned up on florisil columns to be analyzed by gas chromatograph (Agilent 6890) coupled to an electron capture detector (ECD) (Agilent G2397A) and mass spectrometry detector (Agilent 5973 Network) with Agilent MSD Chem software. Ions generated were measured after negative chemical ionization. Analyte concentrations were evaluated by consideration of the per cent recovery of labelled internal standards. The ECD served to verify the detection limits for PCB congeners 28 and 52 (INSPQ, 2009e).
Aroclor 1260 was calculated by INSPQ based on the concentration of PCB 153 and PCB 138 as per CAroclor 1260 = (CPCB 153 + CPCB 138) x 5.2 (NIOSH, 1997; Patterson, 1991).
Average contamination in the laboratory blanks was subtracted from each sample for hexachlorobenzene, PBDE 47 and PBDE 99. Contamination varied depending on how well the source of contamination was controlled during the laboratory analysis (INSPQ, 2010).
Perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexane sulfonate (PFHxS) were extracted with methyl-tert butyl ether in forming an ion pair with tetrabutylammonium hydrogen sulfate. Extracts were evaporated to dryness and dissolved in 200 µL of the mobile phase. They were analyzed by Waters Acquity Ultra Performance Liquid Chromatography (UPLC) coupled to Waters Quattro Premier XE mass spectrometer (MS) and Waters MassLynx software (MS), E-453, operated in the multiple reaction monitoring (MRM) mode with an "electrospray" ion source in the negative mode (INSPQ, 2009f).
Urine samples were thawed at 4°C overnight and shaken vigorously. Samples were stored at room temperature during pipetting, then immediately refrozen. Samples underwent multiple freeze-thaw cycles; 77%, 22%, and 0.8% underwent one, two and three freeze-thaw cycles respectively. 100 µL of urine was fortified with13C12-BPA and buffered to a pH 5. Samples were hydrolyzed with β-glucuronidase for three hours at 37°C, then derivatized with pentafluorobenzyl bromide at 70°C for 2 hours. The derivatized products were extracted with a mixture of dichloromethane-hexane. Evaporated extracts were re-dissolved and analyzed by gas chromatography (Agilent 6890 or 7890) coupled to tandem mass spectrometry detector (Waters Quattro Micro-GC), operating in MRM mode following negative chemical ionization (NCI). The free and hydrolysed forms of BPA were measured together by this procedure. Special precautions were taken to minimize BPA contamination throughout the laboratory analysis. Contamination in the laboratory blanks (deionized water, hydrolyzed and derivatized) was subtracted from each analytical sequence. BPA in the laboratory blanks averaged 0.41 µg/L and ranged from 0.08 to 1.27 µg/L (INSPQ, 2009g; 2010).
Urinary metabolites of diethylphosphate (DEP), dimethyl-phosphate (DMP), diethylthiophosphate (DETP), dimethylthiophosphate (DMTP), diethyldithiophosphate (DEDTP), dimethyldithiophosphate (DMDTP), 2,4-dichlorophenol, and 2,4-dichlorophenoxyacetic acid were hydrolyzed in β-glucuronidase enzyme. The samples were then derivatized with pentafluorobenzyl bromide at 70ºC for 2 hours. The derivatized products were extracted with a mixture of dichloromethane-hexane. Evaporated extracts were re-dissolved and analyzed by GC-MS or GC-MS-MS. The GC-MS method employed gas chromatograph (Agilent 6890) coupled to mass spectrometry detector (Agilent MSD-5973 N or Agilent MSD-5975N), with Agilent Chemstation software operated in the single ion monitoring (SIM) mode following either negative chemical ionization (NCI) or electronic impact (EI). The GC-MS-MS method employed gas chromatography (Agilent 6890 or 7890) coupled to tandem mass spectrometry detector (Waters Quattro Micro-GC) with Waters Masslynx software, operating in MRM mode following NCI (INSPQ, 2009g; 2009h).
Urinary metabolites were hydrolyzed in β-glucuronidase enzyme. The samples were then acidified and extracted with hexane. Extracts were derivatized and extracted a second time with a mixture of isooctane-hexane. Evaporated extracts were dissolved in hexane and analyzed by gas chromatograph (Agilent 6890 N) coupled to a mass spectrometry detector (Agilent 5973 N) with Agilent MSD Chem software operated in the single ion monitoring (SIM) mode following negative chemical ionization (INSPQ, 2009i).
Cotinine was recovered by solid-phase extraction in a 96 well plate format on a Perkin-Elmer JANUS© automated robotic workstation (C-550). Deuterated cotinine was used as the internal standard. The extract was then re-dissolved into 250 µL of mobile phase, and 10 µL was injected into the Waters Acquity Ultra Performance Liquid Chromatography (UPLC) coupled to Waters Quattro Premier XE tandem mass spectrometer (MS) and Waters Masslynx software, operated in the MRM mode with an ion source in "positive electrospray" (INSPQ, 2009j).
Creatinine was measured using the colorimetric end-point Jaffe method. An alkaline solution of sodium picrate reacts with creatinine to form a red Janovski complex using Microgenics DRI "Creatinine-Detect" reagents (#917). The absorbance was read at 505 nm on a Hitachi 917 chemistry autoanalyzer (C-530) (INSPQ, 2009k).
Triglycerides and total cholesterol were measured by enzymatic methods (Health Canada, 2009a; 2009b). Triglycerides were measured using the VITROS TRIG Slide method based on the procedure described by Spayd et al., (1978) and total cholesterol was measured using the VITROS CHOL Slide method based on the procedure proposed by Allain et al., (1974).
Descriptive statistics on the concentration of environmental chemicals in blood and urine of Canadians, aged 6-79 years, were generated using the Statistical Analysis System (SAS) software (SAS Institute Inc., 2002-2003) and the SUDAAN (SUDAAN Release 10.0, 2008) statistical software package.
The CHMS is a sample survey, which means that the respondents "represent" many other Canadians not included in the survey. In order that the results of the survey are representative of the entire population, rather than the sample itself, sample weights were generated by Statistics Canada and incorporated into all estimates presented in this report (e.g., geometric means). Sample weights are used to adjust for the unequal probability of selection into the survey, as well as non-response. Further, to account for the complex survey design of the CHMS, the set of bootstrap weights included with the dataset was used to estimate the 95% confidence intervals for all means and percentiles (Rao et al., 1992; Rust & Rao, 1996).
For each chemical measured, data tables are presented, which include the sample size (n), percentage of results that fall below the limit of detection (% <LOD), arithmetic mean (AM), geometric mean (GM), the 10th, 25th, 50th, 75th, 90th and 95th percentiles and associated 95% confidence intervals (95%CI). Three steps were involved in the calculation of the GM and associated 95% CIs. First, the log of each variable was calculated. Second, the mean and 95% CIs for the log transformed variables were calculated using bootstrap weights. Finally, the GM and associated 95% CIs were calculated by taking the antilog of the log transformed mean and associated 95% CIs. For each chemical, results are presented for the total population as well as by age group and gender. The first cycle of the CHMS was designed to produce national level estimates; as such, site level data is not presented. Measurements that fell below the limit of detection (LOD) for the laboratory analytical method were assigned a value equal to half the LOD. If the proportion of results below the LOD was greater than 40%, geometric and arithmetic means were not calculated. Percentile estimates that are less than the LOD are reported as "< LOD." Appendix B contains a table of LOD values for each chemical. For ease of comparison of data in this report with results from other studies reported in different units, a table of conversion factors is provided in Appendix C.
Chemicals measured in whole blood and plasma are presented as weight of chemical per volume of whole blood or plasma (µg chemical/L blood or plasma, or dL blood in the case of lead). Lipophilic chemicals (i.e., chemicals that accumulate in lipids) measured in plasma, including the organochlorines, PCBs and PBDEs, are presented as weight of chemical per kilogram of total lipid (µg chemical/kg lipid). Lipophilic chemicals concentrate in lipids in the body, including lipids in plasma and serum. Concentrations of these chemicals are reported relative to lipids to reflect the amount of these chemicals that are stored in body fat. Total lipids (g/l) were estimated using the formula:
If a respondent's total cholesterol and/or triglycerides value was missing or <LOD, then the estimate of that respondent's lipid adjusted chemical was also set to missing.
Ideally, the lipids and environmental chemicals would be measured in the same matrix (e.g., plasma) at the same laboratory. However, due to logistical constraints, the environmental chemicals were measured in plasma at INSPQ and lipids (total cholesterol and triglycerides) were measured in serum by the Health Canada Nutrition Laboratory. Several studies have investigated the difference between lipid measurements in plasma or serum and almost all found plasma lipid levels to be slightly lower than serum lipid levels; however, the magnitude of this effect varied considerably among the studies from 1.3% to 6% (Grande et al., 1964; Lab Methods Committee, 1977; Cloey et al., 1990; Wickus & Dukerschein, 1992; Beheshti et al., 1994). In this report, serum lipid levels were not converted to plasma equivalent levels by applying a conversion factor, as these would not necessarily improve the accuracy of the final lipid-adjusted chemical concentrations, when taking into consideration other sources of variability in the measurements of lipids (e.g., inter- and intra-laboratory analytical variability). Variability in lipid measurements can be as great as 10%-15% among laboratories (INSPQ, 2008). Despite these considerations, the reported values for the lipid adjusted environmental chemicals might be underestimateddue to the plasma-serum lipid difference. Further investigation of a potential systematic bias due to plasma-serum lipid differences may be warranted.
For urine measurements, concentrations are presented as weight of chemical per volume of urine (µg chemical/L urine) and adjusted for urinary creatinine (µg chemical/g creatinine). Urinary creatinine is a chemical by-product generated from muscle metabolism and is frequently used to adjust for urine concentration (or dilution) in spot urine samples because its production and excretion are relatively constant over 24 hours due to homeostatic controls (Boeniger et al., 1993; Barr et al., 2005; Pearson et al., 2009). If the chemical measured behaves similarly to creatinine in the kidney, it will be filtered at the same rate, thus expressing the chemical per gram of creatinine helps correct for the effect of urinary dilution as well as some differences in renal function and lean body mass (Barr et al., 2005; Pearson et al., 2009; CDC, 2009). Creatinine is primarily excreted by glomerular filtration in the kidney, and as such, creatinine adjustment may not be appropriate for compounds that are excreted primarily by tubular secretion in the kidney (Teass et al., 2003; Barr et al., 2005). Where urinary creatinine values were missing or <LOD, the estimate of that respondent's creatinine-adjusted chemical was also set to missing.
Descriptive statistics are presented for creatinine (mg/dL) in Appendix D, which include the sample size (n), percentage of results that fall below the limit of detection (% <LOD), arithmetic mean (AM), geometric mean (GM), the 10th, 25th, 50th, 75th, 90th and 95th percentiles, and associated 95% confidence intervals (CI), for the total population as well as by age group and gender. Measurements that fell below the limit of detection (LOD) for the laboratory analytical method were assigned a value equal to half the LOD.
Under the Statistics Act, Statistics Canada is required to ensure respondent confidentiality. Therefore, estimates based on a small number of respondents are suppressed. Following suppression rules for the CHMS, any estimate based on fewer than 10 respondents is suppressed in this report. To avoid suppression, estimates at the 95th percentile require at least 200 respondents; estimates at the 90th and 10th percentiles require at least 100 respondents; estimates at the 75th and 25th percentiles require at least 40 respondents; estimates at the 50th percentile require at least 20 respondents; and, estimates of the arithmetic and geometric means require at least 10 respondents.
Further details on the sample weights and data analysis are available in the Canadian Health Measures Survey (CHMS) Data User Guide: Cycle 1 (Statistics Canada, 2010).
The Canadian Health Measures Survey was designed to provide estimates of environmental chemical concentrations in blood or urine for the Canadian population as a whole. The survey covered approximately 96% of the Canadian population ages 6-79 years; however, the survey was not designed to permit further breakdown of data by collection site. In addition, the CHMS design did not target specific exposure scenarios and consequently, did not select or exclude respondents on the basis of their potential for low or high exposures to environmental chemicals.
Biomonitoring can estimate how much of a chemical is present in a person, but cannot tell you what health effects, if any, may result from that exposure. Our ability to measure environmental chemicals at very low levels has advanced. The presence of a chemical in a person's body does not necessarily mean that it will cause a health effect. Factors such as the dose, the duration and timing of exposure, and the toxicity of the chemical are important to determine whether adverse health effects may occur. For chemicals such as lead or mercury, research studies have provided us with a good understanding of what health risks are associated with different levels in blood. However, for many chemicals, further research is needed to understand the health effects, if any, from different blood or urine concentrations. Furthermore, small amounts of certain chemicals, such as manganese and zinc, are essential for the maintenance of good health, and would be expected to be present in the body. In addition, the way in which a chemical will act in the body will differ among individuals and cannot be predicted with certainty. Certain populations (pregnant women, the elderly, or immuno-compromised people) may be more susceptible to the effects of exposure.
The absence of a chemical does not necessarily mean a person has not been exposed. It may be that the technology is not capable of measuring such a small amount, or that the exposure occurred at an earlier point in time, allowing for the chemical to be eliminated from the person's body before measurement took place.
Biomonitoring cannot tell us the source or route of the exposure. The amount of chemical measured indicates the total amount that enters the body through all routes of exposure (ingestion, inhalation, skin contact) and from all sources (air, water, soil, food, and consumer products). The detection of the chemical may be the result of exposure to a single source or multiple sources. In addition, in most cases biomonitoring cannot distinguish between natural sources and anthropogenic sources. Many chemicals - lead, mercury, cadmium, and arsenic for example - occur naturally in the environment and are also present in anthropogenic products.
With the exception of metals, most of the urine measurements in this survey quantify chemical metabolites. For many chemicals, parent compounds may be broken down (i.e., metabolized) into one or more metabolites. For example, the pyrethroid insecticide cyfluthrin is broken down into several metabolites, including 4-F-3-PBA, cis-DCCA, and trans-DCCA. Some metabolites are specific to one parent compound, while others are common to several parent compounds. Several urinary metabolites are also environmental metabolites (e.g., dialkyl phosphate metabolites) and their presence in urine does not necessarily mean that an exposure to the parent chemical has occurred; rather exposure could be to the metabolite itself in media such as food, water, or air.
Factors that contribute to measured blood and urine levels include the quantity entering the body through all routes of exposure, absorption rates, distribution to various tissues in the body, metabolism, and excretion of the chemical and/or its metabolites from the body. These processes are dependent on both the characteristics of the chemical, including lipophilicity, pH, and particle size, and the characteristics of the individual, such as age, diet, health status, and race (Teass et al., 2003). For these reasons, the way in which a chemical will act in the body will differ among individuals and cannot be predicted with certainty.
This report does not examine trends over time as this is the first survey of this kind conducted in Canada. Results from future cycles of CHMS will be compared to the baseline data from Cycle 1 in order to examine trends in Canadians' exposures to selected environmental chemicals.
More in-depth statistical analysis of the CHMS biomonitoring data, including exploring relationships among environmental chemicals, other physical measures, and self-reported information are beyond the scope of this report and may be performed in the future. The Canadian Health Measures Survey data are being made available to scientists through Statistics Canada's Research Data Centres located across the country and will be a resource for additional scientific analysis.
Phthalate metabolites were measured in Cycle 1 of the CHMS, but the data are not presented in this report due to an ongoing quality assurance investigation into accuracy of the analytical standards used in the laboratory analysis.