Page 2 - Fourth Report on Human Biomonitoring of Environmental Chemicals in Canada
These data tables present national data on concentrations of environmental chemicals in Canadians. These data were collected as part of the Canadian Health Measures Survey (CHMS), an ongoing national direct health measures survey. Statistics Canada, in partnership with Health Canada and the Public Health Agency of Canada, launched the CHMS in 2007 to collect health and wellness data and biological specimens on a nationally representative sample of Canadians. Biological specimens were analyzed for indicators of health status, chronic and infectious diseases, nutritional status, and environmental chemicals.
The CHMS biomonitoring component measures many environmental chemicals and/or their metabolites in blood and urine of survey participants. An environmental chemical can be defined as a chemical substance, either human-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, and consumer products.
The first Report on Human Biomonitoring of Environmental Chemicals in Canada was published in August 2010 and included baseline data for 92 environmental chemicals measured in cycle 1 (Health Canada, 2010a). Data for cycle 1 of the CHMS were collected between March 2007 and February 2009 from approximately 5,600 Canadians aged 6-79 years at 15 sites across Canada.
The Second Report on Human Biomonitoring of Environmental Chemicals in Canada was published in April 2013 (Health Canada, 2013a). Data for cycle 2 were collected between August 2009 and November 2011 from approximately 6,400 Canadians aged 3-79 years at 18 sites across Canada. Cycle 2 included 91 environmental chemicals, 42 of which were also measured in cycle 1.
The Third Report on Human Biomonitoring of Environmental Chemicals in Canada was published in July 2015 (Health Canada, 2015a). Data for cycle 3 were collected between January 2012 and December 2013 from approximately 5,800 Canadians aged 3-79 years at 16 sites across Canada. Cycle 3 included 48 environmental chemicals, 32 of which were also measured in previous cycles.
Data for cycle 4 were collected between January 2014 and December 2015 from approximately 5,700 Canadians aged 3-79 years at 16 sites across Canada. Cycle 4 included 54 environmental chemicals.
A summary of the environmental chemicals measured in cycle 1, cycle 2, cycle 3, and cycle 4 of the CHMS is presented in the Table 1.1. Cycles 3 and 4 were paired so that the same chemicals were measured in both cycles.
|Chemical group||Cycle 1||Cycle 2||Cycle 3||Cycle 4|
|Polybrominated flame retardants||Yes||No||No||No|
|Metals and trace elements||Yes||Yes||Yes||Yes|
|Polycyclic aromatic hydrocarbon metabolites||No||Yes||Yes||Yes|
|Volatile organic compounds: Benzene metabolites||No||Yes||Yes||Yes|
|Pesticides: Organophosphate pesticide metabolites||No||No||YesFootnote a||Yes|
|Volatile organic compounds||No||No||Yes||Yes|
Collection for cycle 5 of the CHMS began in January 2016 and will be completed in late 2017. Planning for future cycles is under way.
In this report, the general CHMS survey design and implementation are described, with emphasis on the biomonitoring component. These sections are 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, health effects, regulatory status, and existing Canadian biomonitoring data.
Data tables specific to each chemical are provided below the relevant text; the tables are broken down by age group and sex, and contain descriptive statistics on the distribution of blood and/or urine concentrations in the sample population. For chemicals that were also measured in previous cycles, data from all cycles are presented together in tables for ease of comparison. Data for chemicals that were only measured in cycle 1 and/or cycle 2 can be found in the first Report on Human Biomonitoring of Environmental Chemicals in Canada (Health Canada, 2010a) or the Second Report on Human Biomonitoring of Environmental Chemicals in Canada (Health Canada, 2013a). Downloadable tables are available through Canada's Open Government portal.
The primary purpose of the biomonitoring component of the Canadian Health Measures Survey (CHMS) is to provide human biomonitoring data to scientists and health and environment officials to aid in assessing exposure to environmental chemicals and in developing policies to reduce exposure to toxic chemicals for the protection of the health of Canadians.
Some specific uses of the CHMS biomonitoring data include the following:
- to establish baseline concentrations of chemicals in Canadians that could allow for comparisons with subpopulations in Canada and with other countries
- to establish baseline concentrations of chemicals to track trends in Canadians over time
- to provide information for setting priorities and taking action to protect the health of Canadians and to protect Canadians from exposure to environmental chemicals
- to assess the effectiveness of health and environmental risk management actions intended to reduce exposures and health risks from specific chemicals
- to support future research on the potential links between exposure to certain chemicals and specific health effects
- to contribute to international monitoring programs, such as the Stockholm Convention on Persistent Organic Pollutants
3 Survey design
The Canadian Health Measures Survey (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 data on important indicators of Canadians' health status, including those pertaining to exposures to environmental chemicals. This information is important in understanding exposure to risk factors, detecting emerging trends in risk factors and exposures, and advancing health surveillance and research in Canada. Detailed descriptions of the CHMS rationale, survey design, sampling strategy, and mobile examination centre (MEC) operations and logistics for cycle 4 have been published (Labrecque and Quigley, 2016; Statistics Canada, 2017).
3.1 Target population
Cycle 4 of the CHMS targets the population aged 3-79 years living in one of the 10 provinces. The following groups are excluded from the survey's coverage: persons living in the three territories; persons living on reserves and other Aboriginal settlements in the provinces; full-time members of the Canadian Forces; the institutionalized population, and residents of certain remote regions. Altogether, these exclusions represent approximately 4% of the target population.
Although the CHMS is not able to provide representative data for the entire Canadian population, there are a number of surveys and research projects carried out in partnership with Health Canada that directly target some of these population gaps.
The First Nations Biomonitoring Initiative (FNBI) is a survey carried out by the Assembly of First Nations and Health Canada that seeks to establish baseline biomonitoring data for First Nations people living on-reserve south of the 60° parallel (AFN, 2013). Between 2009 and 2011, the FNBI measured the levels of 97 environmental chemicals in blood and urine samples collected from 503 participants living in 13 First Nation communities across Canada. The complete report has been published by the Assembly of First Nations (AFN, 2013).
In addition, numerous biomonitoring studies have been undertaken in Canada's North through the Northern Contaminants Program (NCP). The NCP, which is managed by federal government departments, provincial and territorial agencies, and Aboriginal organizations, was established in 1991 to respond to concerns about human exposure to contaminants in traditional diets of Northern Aboriginal peoples. The NCP provides funding for numerous individual studies undertaken in various regions of the North, including the Northwest Territories, Nunavut, and Nunavik (Quebec's North). More detailed information and results from these studies have been summarized in the Canadian Arctic Contaminants Assessment Reports and numerous scientific articles.
3.2 Sample size and allocation
To meet the objective of producing reliable estimates at the national level by age group and sex, cycle 4 of the CHMS required a minimum sample of at least 5,700 participants. The participants were distributed among six age groups (3-5, 6-11, 12-19, 20-39, 40-59, and 60-79 years) and sex (except for 3-5 years), for a total of 11 groups. For the 3- to 5-year age group, the survey was not designed to provide estimates for the individual sexes.
3.3 Sampling strategy
To meet the requirements of the CHMS, a multi-stage sampling strategy was used.
3.3.1 Sampling of collection sites
The CHMS required participants to report to a MEC and be able to travel to the centre within a reasonable period of time. For cycle 4, the 2011 Census geography was used to create 360 collection sites across the country. A geographic area with a population of at least 10,000 and a maximum participant travel distance of 75 kilometres (50 kilometres in urban areas and 75 kilometres in rural areas) were required for the location of collection sites. Areas not meeting these criteria were excluded.
A larger number of collection sites would have optimized the precision of the estimates. However, the logistical and cost constraints associated with the use of MECs restricted the number of collection sites to 16. The 16 collection sites were selected from within the five standard regional boundaries used by Statistics Canada (Atlantic, Quebec, Ontario, the Prairies, and British Columbia); they were allocated to these regions in proportion to the size of the population. Although not every province in Canada had a collection site, the CHMS sites were chosen to represent the Canadian population in all 10 provinces, east to west, including larger and smaller population densities. The collection sites selected for cycle 4 of the CHMS are listed in Table 188.8.131.52.
Table 184.108.40.206 - Canadian Health Measures Survey cycle 4 (2014-2015) collection sites
- Shelburne-Argyle, N.S.
- South Fredericton, N.B.
- West Laval
- West Montréal
- North Toronto
- Thunder Bay
- West Hamilton
- West Toronto
- Central and eastern Edmonton, Alta.
- East Regina, Sask.
3.3.2 Dwelling and participant sampling
Within each site, dwellings with known household composition at the time of the 2011 Census, updated with the most recent information from administrative files, were stratified by age of household residents at the time of the survey, with the six age-group strata corresponding to the CHMS cycle 4 age groups (3-5, 6-11, 12-19, 20-39, 40-59, and 60-79 years). 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; this list was used to select the survey participants. One or two people were selected, depending on the household composition.
3.4 Selection of environmental chemicals
The process to determine the list of environmental chemicals to be included in cycles 3 and 4 of the CHMS built upon the existing consultation process used for cycle 2. The primary mechanism of consultation for cycle 2 was through a questionnaire distributed to key stakeholders with expertise or interest in human biomonitoring of environmental chemicals; the purpose was to define specifically what should be measured in blood and urine samples in the Canadian population. Key participants included various internal Health Canada branches and programs as well as a number of external groups, including other federal departments, provincial/territorial health and environment departments, industry groups, environment and health non-governmental organizations, and academics. Through this consultation, over 310 different chemicals and metabolites were nominated.
Selection was based on health risks; evidence of human exposure; existing data gaps; commitments under national and international treaties, conventions, and agreements; availability of standard laboratory analytical methods; and current and anticipated health policy development and implementations.
The following criteria were used as a general guide for identifying and selecting the environmental chemicals to include in the CHMS:
- seriousness of known or suspected health effects related to the substance
- need for public health actions related to the substance
- level of public concern about exposures and possible health effects related to the substance
- evidence of exposure of the Canadian population to the substance
- feasibility of collecting biological specimens in a national survey and associated burden on survey participants
- availability and efficiency of laboratory analytical methods
- costs of performing the test
- parity of selected chemicals with other national and international surveys and studies
Because fewer than 2 years had passed between the selection processes for cycle 2 and cycles 3 and 4, it was determined that an entirely new consultation was unnecessary; rather, the existing priority list from cycle 2 was used as the starting point for cycles 3 and 4. Chemicals that were included in the cycle 2 priority list, which could not previously be included for various reasons, were given highest priority for inclusion in cycles 3 and 4. In addition, environmental chemicals from cycles 1 and 2 considered to be high priorities were carried forward into cycles 3 and 4. Ultimately, the list was narrowed by the volume of biospecimens available from survey participants to conduct the analyses. Blood volume is generally limited; it is also required for analyses of chronic and infectious diseases and nutritional biomarkers. Thus, fewer environmental chemicals were measured in blood than in urine.
A full list of the chemicals measured in individual respondents in CHMS cycle 4 is presented in Table 3.4.1.
|Chemical||Cycle 1||Cycle 2||Cycle 3||Cycle 4|
|Acrylamide haemoglobin adduct||No||No||Yes||Yes|
|Glycidamide haemoglobin adduct||No||No||Yes||Yes|
|Metals and trace elements|
|Arsenocholine and arsenobetaine||No||Yes||Yes||Yes|
|Organophosphate pesticide metabolites|
|Malathion dicarboxylic acid||No||No||YesFootnote a||Yes|
|Methyl paraben||No||No||YesFootnote a||Yes|
|Ethyl paraben||No||No||YesFootnote a||Yes|
|Propyl paraben||No||No||YesFootnote a||Yes|
|Butyl paraben||No||No||YesFootnote a||Yes|
|Polycyclic aromatic hydrocarbon metabolites|
|Volatile organic compounds|
|m-Xylene & p-Xylene||No||No||Yes||Yes|
Owing to the high cost of laboratory analyses, some environmental chemicals were not measured for all CHMS participants. The majority of the environmental chemicals were measured in a subsample of 2,500 participants aged 3-79 years, with the following exceptions: lead, cadmium, total mercury, and cotinine were measured in all participants; methylmercury was measured in 1,000 participants aged 20-79 years; and trihalomethanes and volatile organic compounds were measured in 2,500 participants aged 12-79 years. Further details on the subsampling for environmental chemicals are available in the Canadian Health Measures Survey (CHMS) Data User Guide: Cycle 4 (Statistics Canada, 2017) and in Sampling documentation for cycle 4 of the Canadian Health Measures Survey (Labrecque and Quigley, 2016).
|Measure||Matrix||Target sample size||Age (years)|
|Metals and trace elements||Urine, blood||5,700||Yes||Yes||Yes||Yes||Yes||Yes|
|Metals and trace elements: Arsenic||Urine||2,500||Yes||Yes||Yes||Yes||Yes||Yes|
|Metals and trace elements: Fluoride||Urine||2,500||Yes||Yes||Yes||Yes||Yes||Yes|
|Metals and trace elements: Methylmercury||Blood||1,000||No||No||No||Yes||Yes||Yes|
|Organophosphate pesticide metabolites||Urine||2,500||Yes||Yes||Yes||Yes||Yes||Yes|
|Polycyclic aromatic hydrocarbon metabolites||Urine||2,500||Yes||Yes||Yes||Yes||Yes||Yes|
|Volatile organic compounds (VOCs)||Blood||2,500||No||No||Yes||Yes||Yes||Yes|
|VOCs: Benzene metabolites||Urine||2,500||Yes||Yes||Yes||Yes||Yes||Yes|
3.5 Ethical considerations
Personal information collected through the CHMS is protected under the federal Statistics Act (Canada, 1970-71-72). Under the 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; this includes physical, organizational, and technological measures. The steps taken by Statistics Canada to safeguard the information collected in the CHMS have been described previously (Day et al., 2007).
Ethics approval for all components of the CHMS was obtained from the Health Canada and Public Health Agency of Canada Research Ethics Board. Informed written consent for the MEC portion of the CHMS was obtained from participants older than 14 years of age. For younger children, a parent or legal guardian provided written consent, and the child provided assent. Participation in this survey was voluntary, and participants could opt out of any part of the survey at any time.
A strategy was developed to communicate results to survey participants with the advice and expert opinion of the CHMS Laboratory Advisory Committee, the Physician Advisory Committee, l'Institut national de santé publique du Québec (the reference laboratory performing some of the environmental chemical analyses), and Health Canada's Research Ethics Board (Day et al., 2007). For the environmental chemicals, only results for lead and mercury were actively reported to participants. However, participants could receive all other test results upon request to Statistics Canada. More information on reporting to participants, including the ethical challenges encountered, can be found in Haines et al. (2011).
Fieldwork for the Canadian Health Measures Survey (CHMS) cycle 4 took place over a period of 2 years from January 2014 to December 2015. Data were collected sequentially at 16 sites across Canada. The sites were ordered to take into account seasonality by region and the temporal effect, subject to operational and logistical constraints.
Statistics Canada mailed an advance letter and brochure to households that were selected as outlined in the Dwelling and Participant Sampling section. The mailing informed potential participants that they would be contacted for the survey's data collection.
Data were collected from consenting survey participants through a household personal interview, using a computer-assisted method, and a visit to a mobile examination centre (MEC) for physical measures and biospecimen collection. The field team consisted of household interviewers and the CHMS MEC staff, including trained health professionals who performed the physical measures testing (Statistics Canada, 2017).
Participants were first administered a household questionnaire in their home. Using a computer application, the interviewer randomly selected one or two participants and conducted separate 45- to 60-minute health interviews (Statistics Canada, 2017). The interviews collected demographic and socio-economic data and information about lifestyle, medical history, current health status, the environment, and housing conditions. At this time, the collection protocol for the tap water component of the survey was also initiated. Within approximately 2 weeks after the home visit, participants visited the MEC. Each MEC consisted of three trailers linked by enclosed pedestrian walkways. One trailer was for reception and contained an administration area and an examination room; the second trailer contained a laboratory, a phlebotomy (blood collection) room, and examination rooms; and the third trailer contained additional examination rooms. The MEC operated 7 days a week in order to complete approximately 350 visits at each site over 5 to 6 weeks and to accommodate participants' schedules (Statistics Canada, 2017). MEC appointments averaged about 2.5 hours. A parent or legal guardian accompanied children under 14 years of age. To maximize response rates, participants who were unable or unwilling to go to the MEC were offered the option of a home visit by members of the CHMS MEC staff to perform some of the physical measures and the biospecimen collection portion of the survey (Statistics Canada, 2017). At the end of the MEC visit, a subsample of households was asked to place a sampler in their home as part of the indoor air component of the survey.
At the start of the MEC visit, participants signed consent/assent forms prior to any testing and in most cases provided a urine sample immediately thereafter. For logistical purposes, spot samples were collected rather than 24-hour urine samples. The urine samples were collected using the first-catch urine, as opposed to the mid-stream urine collected in cycle 1. Guidelines were provided to participants asking them to abstain from urinating 2 hours prior to their MEC visit. Samples were collected in 120 mL urine specimen containers. Trained health professionals took physical health measurements such as height, weight, blood pressure, lung function, and physical fitness. A series of screening questions were administered to participants to determine their eligibility for the various tests, including phlebotomy, based on pre-existing exclusion criteria (Statistics Canada, 2017). Blood specimens were drawn by a certified phlebotomist; the maximum amount depended upon the age of the participant. The approximate volume drawn from participants aged 3-5 years was 22.0 mL; 6-11 years, 28.5 mL; 12-13 years, 48.8 mL; 14-19 years, 52.8 mL; and 20-79 years, 72.8 mL.
All blood and urine specimens collected in the MEC were processed and aliquoted in the MEC. Biospecimens were stored temporarily in temperature-monitored freezers at −30°C until shipping, with the exception of blood samples collected for volatile organic compound analysis; these were refrigerated. Once a week, the specimens were shipped on dry ice or in monitored refrigerated conditions to the reference laboratory for analyses. Standardized operating procedures were developed for the collection of blood and urine specimens, processing and aliquoting procedures, as well as for shipping biospecimens to ensure adequate data quality and to standardize data collection. A priority sequence for laboratory analyses was established in the event that an insufficient volume of biospecimen was collected for complete analyses of the environmental chemicals as well as for analyses of infectious diseases, nutritional status, and chronic diseases. Details on the collection tubes, aliquot volumes, and priority testing are presented in Table 4.1.
|Measure||Matrix||Collection Tube (size and typeFootnote a)||Optimal VolumeFootnote b|
|Acrylamide||Whole Blood||4.0, 6.0, or 10mLFootnote c Lavender EDTAFootnote d||1.5 mL|
|Methylmercury||1.8 mLFootnote e|
|Volatile organic compounds (VOCs)||Whole Blood||10 mL Washed Grey||10 mL|
|Creatinine||Urine||120 mL urine specimen container||0.5 mL|
|Arsenic (speciated)||1.0 mL|
|Nicotine metabolite||0.8 mL|
|Inorganic mercury||1.5 mL|
|Environmental phenols||0.8 mL|
|Organophosphate pesticide metabolites||4.0 mL|
|Polycyclic aromatic hydrocarbon metabolites (PAHs) and benzene metabolites||12 mL|
|Specific gravity||0.3 mL|
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 MEC 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 consistent measurement techniques, procedure manuals and training guides were developed in consultation with, and reviewed by, experts in the field. Quality control samples were done at each site, consisting of three field blanks per site (deionized water for most analytes), blind replicates (three pairs per site except blood VOCs and cotinine), and blind control samples (approximately six per site).
The quality control samples were sent to the laboratory with regular specimen shipments. Quality control sample 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. The replicates were used to assess the precision of the analysis in pre-established acceptable ranges. If required, feedback was provided quickly to the reference laboratory for review and remedial action.
Beginning in cycle 2, a subsample of CHMS participants' households was selected for a component that involved sampling of indoor air over a 7-day period. A tap water sampling protocol was introduced in cycle 3 to complement the indoor air component. By sampling both indoor air and tap water in the home environment, where Canadians spend the majority of their time, two potential sources of exposure to environmental chemicals are captured.
Participants were asked to place the indoor air sampler in their household for 7 days in order to measure a number of VOCs. One indoor air sampler was given per selected household, along with a pencil, a postage-paid envelope, and an information sheet. After the 7-day collection period was over, participants mailed their indoor air sampler in the envelope provided to CASSEN Testing Laboratories where all indoor air analyses were performed.
The tap water sampling was carried out during the household interview by the interviewer and lasted for approximately 10 minutes. The objective of tap water collection was to determine the prevalence of and characterize the distribution of exposure to fluoride and to VOCs from tap water. Two samples were collected at each household and were shipped to the laboratories where the tap water analysis was performed. Fluoride samples were analyzed by the Laboratoire de santé publique du Québec whereas the VOC samples were analyzed by a Health Canada research laboratory.
Indoor air results were not reported back to respondents; however, the tap water test results were reported back to those who participated in both the household and the clinic portion of the survey. Reports included results for those chemicals for which either aesthetic quality or maximum acceptable concentration (MAC) guidelines have been established by the Federal-Provincial-Territorial Committee on Drinking Water. Aesthetic objectives address concentrations that could affect the taste, smell, or colour of water, while still being below the point at which health effects could appear whereas MACs are established on the basis of health considerations. Certain chemicals measured in the tap water sample do not have established guidelines; respondents were able to receive these results only upon request. If one or more of the tap water results was found to exceed a MAC, survey staff contacted the respondents to inform them of their result and to ask for their consent to share the result with provincial authorities.
A complete list of the substances measured in the indoor air and tap water samples is available in the Canadian Health Measures Survey (CHMS) Content summary for cycles 1 to 8 (Statistics Canada, 2013a). Further details on the indoor air study and tap water sampling are available in the Canadian Health Measures Survey (CHMS) Data User Guide: Cycle 4 (Statistics Canada, 2017). Indoor air and tap water data are available upon request by contacting Statistics Canada at firstname.lastname@example.org.
Detailed descriptions of the CHMS MEC operations and logistics have been described previously in Bryan et al. (2007) and are presented in the Canadian Health Measures Survey (CHMS) Data User Guide: Cycle 4 (Statistics Canada, 2017).
5 Laboratory analyses
Laboratory analyses of environmental chemicals and creatinine were performed at analytical laboratories within Health Canada and l'Institut national de santé publique du Québec (INSPQ). Laboratories developed standardized operating procedures for the analytical methods used to measure environmental chemicals or their metabolites in biological samples. Analytical accuracy and precision of measurements were evaluated through rigorous method validation programs at each laboratory.
Internal quality control measures within each laboratory included the analysis of calibration standards, laboratory blanks, method blanks, and in-house quality control samples in each analytical batch. In addition, laboratories conducted periodical analyses of Standard Reference Materials/Certified Reference Materials when available. Quality assurance reviews were conducted on laboratory data on a regular basis to evaluate any issues in the batch processing and to identify inconsistencies in analytical results. Appropriate corrective measures were taken when required. As part of external quality control measures, laboratories participated in external quality control programs and inter-laboratory comparison studies when available. A table is provided with limits of detection for each method (Appendix A). The methods used in the analyses of the environmental chemicals and creatinine are described below.
Whole blood was thawed at room temperature and reacted with modified Edman reagent (pentafluorophenyl isothiocyanate) for 2 hours at 55°C. The sample was purified using solid phase extraction on Isolute HM-N sorbent. Analytes were then eluted with diisopropyl ether/ethyl acetate/toluene (50/40/10 v/v/v) and the extract was evaporated under a stream of nitrogen. The sample was reconstituted in methanol/water (40/60 v/v) and analyzed using a Waters Acquity ultra performance liquid chromatograph (UPLC) system coupled to a Quattro Premier tandem mass spectrometer (Health Canada, 2014a).
5.2 Environmental phenols
For the analysis of bisphenol A and triclosan, urine samples were subjected to enzymatic hydrolysis (β-glucuronidase enzyme). The samples were 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 dissolved in the appropriate solvent and analyzed using an Agilent 6890 or 7890 gas chromatographic system coupled to a Waters Quattro Micro gas chromatograph (GC) tandem mass spectrometer. The mass spectrometer was operated in the negative ion chemical ionization mode and the analytes were quantified using multiple reaction monitoring (MRM) (INSPQ, 2014a). Free and hydrolyzed forms of bisphenol A were measured together by this procedure.
5.3 Metals and trace elements
Urine samples were diluted in ammonium carbonate solution and analyzed for arsenite (As3+), arsenate (As5+), monomethylarsonic acid, dimethylarsinic acid, and the sum of arsenobetaine and arsenocholine using a Waters Acquity UPLC coupled to a Varian 820-MS inductively coupled plasma-mass spectrometer (ICP-MS) system (INSPQ, 2009a). For arsenocholine, urine was diluted with formic acid and acetonitrile solution and analyzed on Waters Acquity UPLC coupled to a TQ-S tandem mass spectrometer (INSPQ, 2009a).
5.3.2 Cadmium, lead, and total mercury
Blood samples were diluted in a basic solution containing octylphenol ethoxylate and ammonia. They were analyzed for cadmium, lead, and total mercury using a Perkin Elmer Sciex Elan DRC II ICP-MS. Matrix matched calibration was performed using blood from non-exposed individuals (INSPQ, 2010).
Urine samples were diluted with ionic adjustment buffer and analyzed using an Orion pH meter with a fluoride ion selective electrode (Orion Research Inc.) (INSPQ, 2009b).
5.3.4 Inorganic mercury
Urine was digested in nitric acid at 50°C, diluted, and analyzed for inorganic mercury on a Perkin Elmer FIMS 100 (cold vapour system). Matrix matched calibration was performed using urine from non-exposed individuals (INSPQ, 2009c).
Methylmercury was extracted by sonication from whole blood using an L-cysteine acid solution. After centrifugation, proteins were precipitated using acetonitrile. The supernatant was extracted using a micro coaxial solid phase extraction cartridge. The extract was evaporated to dryness, reconstituted in the appropriate solvent, and analyzed using a Waters Acquity UPLC coupled to a Varian 820-MS ICP-MS (INSPQ, 2011).
5.4 Nicotine metabolite
Free cotinine was measured in participants aged 3-11 years (INSPQ, 2009d), and free cotinine and other tobacco biomarkers were measured in participants aged 12-79 years (INSPQ, 2015a). In both methods, free cotinine was recovered from urine samples by solid-phase extraction on an automated Janus workstation. Deuterated cotinine was used as the internal standard. The extract was redissolved in the mobile phase, analyzed using a Waters Acquity UPLC coupled to a Waters Quattro Premier XE tandem mass spectrometer with an electrospray ionization source operating in positive ion mode, and the analytes were quantified using MRM. Data from the two methods were combined and are presented together in tables for the total population aged 3-79 years.
5.5 Organophosphate pesticide metabolites
Malathion dicarboxylic acid (DCA) was measured in urine. The analyte was spiked with DCA analogue isotopically labeled with carbon 13. The two compounds were extracted on an ion-exchange cartridge, eluted, evaporated to dryness, resuspended in ethyl acetate, and then derivatized with MTBSTFA and analyzed using an Agilent 7890 GC coupled to an Agilent 7000B triple-quad tandem mass spectrometer with ions measured in MRM mode with a source in electron ionization mode (INSPQ, 2015b).
The total form (conjugated and free) of 3,5,6-trichloro-2-pyridinol was measured in urine. The urine sample was spiked with TCPy analogue isotopically labeled with carbon 13 and hydrolyzed at 37°C with the enzyme β-glucuronidase/arylsulfatase. The compound and its isotopically labeled analogue were derivatized at 60°C in the presence of dansyl chloride. The compounds were then extracted with hexane. The extracts were dried, resuspended in an acetonitrile:MeOH:water mixture, and analyzed using a Waters Acquity ultrahigh performance liquid chromatograph coupled to a Waters Xevo TQ-S tandem mass spectrometer in MRM mode with an electrospray source in positive mode (INSPQ, 2015c).
For the analysis of butyl paraben, ethyl paraben, methyl paraben, and propyl paraben, urine samples were subjected to enzymatic hydrolysis (β-glucuronidase enzyme). The samples were then acidified and preconcentrated by Solid Phase Extraction. Evaporated extracts were dissolved in the appropriate solvent and analyzed using a Waters Acquity UPLC coupled to a Waters Quattro Premier XE tandem mass spectrometer. The mass spectrometer was operated in the negative ion electrospray ionization mode and the analytes were quantified using MRM. Free and hydrolyzed forms of parabens in urine were measured together by this procedure (Health Canada, 2016a).
5.7 Polycyclic aromatic hydrocarbon metabolites
For the analysis of polycyclic aromatic hydrocarbon metabolites (3-hydroxybenzo[a]pyrene, 2-hydroxychrysene, 3-hydroxychrysene, 4-hydroxychrysene, 6-hydroxychrysene, 3-hydroxyfluoranthene, 2-hydroxyfluorene, 3-hydroxyfluorene, 9-hydroxyfluorene, 1-hydroxynaphthalene, 2-hydroxynaphthalene, 1-hydroxyphenanthrene, 2-hydroxyphenanthrene, 3-hydroxyphenanthrene, 4-hydroxyphenanthrene, 9-hydroxyphenanthrene, and 1-hydroxypyrene), urine samples were hydrolyzed using β-glucuronidase enzymatic solution and extracted with an organic solvent at neutral pH. The extracts were evaporated, derivatized with N-methyl-N-(trimethylsilyl)-trifluoroacetamide, and analyzed using an Agilent 7890 GC coupled to an Agilent 7000B triple-quad tandem mass spectrometer operating in electron impact ionization mode. Analytes were quantified using MRM (INSPQ, 2014b).
5.8 Volatile organic compounds
Whole blood samples were withdrawn using a previously cleaned air-tight syringe, transferred to a glass vial, and a mixture of isotopically labelled analogs was added. The vial was crimp-sealed and placed in a temperature-controlled autosampler tray. The samples were maintained at 40°C with continuous mixing. The analytes (benzene, toluene, ethylbenzene, m-xylene, o-xylene, p-xylene, chloroform, bromoform, bromodichloromethane, dibromochloromethane, trichloroethane, tetrachloroethene, and styrene) were extracted by inserting a solid phase microextraction fiber into the vial headspace. After extraction, the fiber was transferred to a heated GC inlet where the analytes were rapidly desorbed off the fiber. The analytes were focused using a Thermo Fisher Scientific cryotrap (Cryotrap 915) and analyzed using a Thermo Fisher Scientific TRACE™ ultra GC coupled to a TSQ Quantum XLS mass spectrometer equipped with electron ionization source. The analytes were quantified in selected reaction monitoring mode (Aranda-Rodriguez, 2015; Health Canada, 2012a).
5.8.1 Benzene metabolites
Benzene metabolites (trans,trans-muconic acid and S-phenylmercapturic acid) were extracted from urine using a hydrophilic-lipophilic-balanced solid-phase extraction cartridge on an automated Janus workstation. The extracts were evaporated to dryness, reconstituted in the mobile phase, and analyzed using a Waters Acquity UPLC coupled to a Waters Xevo TQ-S tandem mass spectrometer operated in negative ion mode (INSPQ, 2014c).
Creatinine was measured in urine using the colorimetric end-point Jaffe method. An alkaline solution of sodium picrate reacts with creatinine in urine 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 (INSPQ, 2008).
6 Statistical data analyses
Descriptive statistics on the concentrations of environmental chemicals in the blood and urine of Canadians, aged 3-79 years, were generated using the Statistical Analysis System software (SAS Institute Inc., version 9.2, 2008) and the SUDAAN® (SUDAAN Release 11.0.1, 2013) statistical software package.
The Canadian Health Measures Survey (CHMS) is a sample survey, meaning that the participants represent many other Canadians not included in the survey. In order for the results of the survey to be representative of the entire population, sample weights were generated by Statistics Canada and incorporated into all estimates presented in the data tables (e.g. geometric means). Survey weights were used to take into account 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 data set was used to estimate the 95% confidence intervals (CIs) for all means and percentiles (Rao et al., 1992; Rust and Rao, 1996).
For each chemical measured in cycle 4, data tables are presented. Data from cycles 1, 2, and 3 are also provided within the tables for those substances measured in all cycles. In the first Report on Biomonitoring of Environmental Chemicals in Canada, results for cycle 1 were reported to two decimal places. For cycles 2, 3, and 4 of the CHMS, the reporting protocol changed and the results were reported to two significant digits. For consistency, cycle 1 data were adjusted to two significant digits before generating the descriptive statistics, and data from all cycles are presented to two significant digits. Therefore, the descriptive statistics presented for cycle 1 may differ from those presented in the first report. The differences are not significant and the values presented in the first report are still considered to be accurate.
The data tables include the sample size (n); percentage of results that fall below the limit of detection (LOD); geometric mean (GM); the 10th, 50th, 90th, and 95th percentiles; and associated 95% CIs. For each chemical, results are presented for the total population as well as by age group and sex. For each chemical that was measured in multiple cycles of the CHMS, a summary table is provided that compares results for the aggregate of all age groups common to all cycles and for that same aggregate population separated by sex. Measurements that fell below the 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%, GMs were not calculated. Percentile estimates that are less than the LOD are reported as <LOD. The appendices contain tables of LOD values for each chemical, specific to each cycle, and conversion factors to assist in the comparison of data from other studies that report different units (Appendices A and B).
Chemicals measured in whole blood are presented as weight of chemical per volume of whole blood (e.g. µg chemical/L blood).
For urine measurements, concentrations are presented as weight of chemical per volume of urine (e.g. µg chemical/L urine) and adjusted for urinary creatinine (e.g. µg chemical/g creatinine). Urinary creatinine is a chemical by-product generated from muscle metabolism; it 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 owing to homeostatic controls (Barr et al., 2005; Boeniger et al., 1993; 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 adjust for the effect of urinary dilution as well as some differences in renal function and lean body mass (Barr et al., 2005; CDC, 2009; Pearson et al., 2009). Creatinine is primarily excreted by glomerular filtration; therefore, creatinine adjustment may not be appropriate for compounds that are excreted primarily by tubular secretion in the kidney (Barr et al., 2005; Teass et al., 2003). In addition, creatinine excretion can vary owing to age, sex, and ethnicity; therefore, it may not be appropriate to compare creatinine-adjusted concentrations among different demographic groups (e.g. children with adults) (Barr et al., 2005). Where urinary creatinine values were missing or <LOD, the estimate of that participant's creatinine-adjusted chemical was not calculated and was also set to missing.
Descriptive statistics are available for creatinine (mg/dL) (Appendix C). These include n; GM; the 10th, 50th, 90th, and 95th percentiles; and associated 95% CIs for the total population as well as by age group and sex.
Specific gravity was also measured in all urine samples immediately following sample collection at the mobile examination centre. Urinary specific gravity is the ratio of densities between urine and pure water and can be used to adjust for variations in urine output, similar to urinary creatinine adjustment. Urinary specific gravity adjustment has not been presented for any of the chemicals; however, specific gravity data are available upon request by contacting Statistics Canada at email@example.com should researchers wish to perform this adjustment for their own data analyses.
Under the Statistics Act, Statistics Canada is required to ensure participant confidentiality. Therefore, estimates based on a small number of participants are suppressed. Following suppression rules for the CHMS, any estimate based on fewer than 10 participants is suppressed in the data tables. To avoid suppression, estimates at the 95th percentile require at least 200 participants, estimates at the 10th and 90th percentiles require at least 100 participants, estimates at the 50th percentile require at least 20 participants, and estimates of the geometric mean require at least 10 participants.
Estimates from a sample survey inevitably include sampling errors. Measuring the possible scope of sampling errors is based on the standard error of the estimates drawn from the survey results. To get a better indication of the size of the standard error, it is often more useful to express the standard error in terms of the estimate being measured. The resulting measure, called the coefficient of variation (CV), is obtained by dividing the standard error of the estimate by the estimate itself, and it is expressed as a percentage of the estimate. This report employs the following Statistics Canada guidelines for releasing estimates based on their CV:
- When a CV is between 16.6% and 33.3%, an estimate can be considered for general unrestricted release but is accompanied by a warning cautioning subsequent users of the high sampling variability associated with the estimate. These estimates are identified by the superscript letter E.
- When a CV is greater than 33.3%, Statistics Canada recommends not releasing the estimate because conclusions based on these data will be unreliable and most likely invalid. These estimates will not be published and will instead be replaced by the letter F.
Further details on the sample weights and data analysis are available in the Canadian Health Measures Survey (CHMS) Data User Guide: Cycle 4 (Statistics Canada, 2017).
7 Considerations for interpreting the biomonitoring data
The Canadian Health Measures Survey (CHMS) was designed to provide estimates of environmental chemical concentrations in blood or urine for the Canadian population as a whole. The first cycle of the survey covered approximately 96% of the Canadian population aged 6-79 years. The second, third, and fourth cycles included children as young as 3 years of age and also covered approximately 96% of the Canadian population aged 3-79 years of age. The survey was not designed to permit breakdown of data by region, province, or collection site, although some analysis is possible if data from more than one cycle are combined (see Instructions for Combining Multiple Cycles of Canadian Health Measures Survey [CHMS] Data [Statistics Canada, 2015]). In addition, the CHMS design did not target specific exposure scenarios; consequently, it did not select or exclude participants 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 it cannot say what health effects, if any, may result from that exposure. The ability to measure environmental chemicals at very low concentrations has advanced in recent years. However, the presence alone 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 toxicity of the chemical, and the duration and timing of exposure are important to determine whether potential adverse health effects may occur. For chemicals such as lead or mercury, research studies have provided a good understanding of the health risks associated with different concentrations in blood. However, for many chemicals, further research is needed to understand the potential 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 (children, 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 detecting 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 has entered the body through all routes of exposure (ingestion, inhalation, and 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 and anthropogenic sources. Many chemicals (lead, mercury, cadmium, and arsenic) occur naturally in the environment and are also present in human-made products.
While metals are measured in urine as the parent compounds, almost all other chemicals are measured as metabolites. For many chemicals, parent compounds may be broken down (i.e. metabolized) in the body into one or more metabolites. For example, the polycyclic aromatic hydrocarbon chrysene is broken down into several metabolites. Some metabolites are specific to one parent compound whereas others are common to several parent compounds. Several urinary metabolites are also formed in the environment (e.g. chlorpyrifos metabolites). 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 the concentrations of chemicals measured in blood and urine 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, also called toxicokinetics, depend on both the characteristics of the chemical, including its solubility in fat (or lipophilicity), its pH, its particle size, and the characteristics of the individual being exposed, such as age, diet, health status, and ethnicity. For these reasons, the way in which a chemical will act in the body will differ among individuals and cannot be predicted with certainty.
The CHMS biomonitoring data currently available include temporal data for substances measured in cycle 1 (2007-2009), cycle 2 (2009-2011), cycle 3 (2012-2013), and cycle 4 (2014-2015). Results from future cycles can be compared with the baseline data from the CHMS in order to begin to examine trends in Canadians' exposures to selected environmental chemicals. It is important to note that there were some sampling and analytical modifications between cycles that may have contributed some variation in results for those substances measured in multiple cycles. The limits of detection (LOD) for certain analytical methods have changed from cycle to cycle. Although the LOD values did not change by a large margin, this difference should be noted when comparing data from multiple cycles. A list of LOD values from cycles 1, 2, 3, and 4 is provided (Appendix A). In addition, the urine collection protocol and guidelines were changed in cycle 2, and this may have resulted in a shift in creatinine levels when cycle 1 data are compared with those from subsequent cycles. This, in turn, could affect creatinine-adjusted levels of some chemicals.
Urinary creatinine concentrations can also be affected by variables such as age, sex, and ethnicity resulting in differences among demographic groups within a single cycle (Mage et al., 2004). In particular, creatinine excretion per unit bodyweight increases substantially with increasing age in children (Aylward et al., 2011; Remer et al., 2002). As a result, it is acceptable to compare creatinine-adjusted concentrations among similar demographic groups (e.g. children with children, adults with adults, males with males) but not among two different demographic groups (e.g. children with adults, males with females) (Barr et al., 2005).
More in-depth statistical analyses of the CHMS biomonitoring data, including time trends, exploring relationships among environmental chemicals, other physical measures, and self-reported information are being published by researchers in the scientific literature. A bibliography of publications using CHMS data is available. CHMS data are available to scientists through Statistics Canada's Research Data Centres Program and are a resource for additional scientific analyses. Further information about the CHMS can be obtained by contacting Statistics Canada at firstname.lastname@example.org.
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