Application of the Cytokinesis-Block Micronucleus Assay for High-Dose Exposures Using Imaging Flow Cytometry.

The cytokinesis-block micronucleus assay is a well-established method to assess radiation-induced genetic damage in human cells. This assay has been adapted to imaging flow cytometry (IFC), allowing automated analysis of many cells, and eliminating the need to create microscope slides. Furthermore, to improve the efficiency of assay performance, a small-volume method previously developed was employed. Irradiated human blood samples were cultured, stained, and analyzed by IFC to produce images of the cells. Samples were run using both manual and 96-well plate automated acquisition. Multiple parameter-based image features were collected for each sample, and the results were compared to confirm that these acquisition methods are functionally identical. This paper details the multi-parametric analysis developed and the resulting calibration curves up to 10 Gy. The calibration curves were created using a quadratic random coefficient model with Poisson errors, as well as a logistic discriminant function. The curves were then validated with blinded, irradiated samples, using relative bias and relative mean square error. Overall, the accuracy of the dose estimates was adequate for triage dosimetry (within 1 Gy of the true dose) over 90% of the time for lower doses and about half the time for higher doses, with the lowest success rate between 5 and 6 Gy where the calibration curve reached its peak and there was the smallest change in MN/BNC with dose. This work describes the application of a novel multi-parametric analysis that fits the calibration curves and allows dose estimates up to 10 Gy, which were previously limited to 4 Gy. Furthermore, it demonstrates that the results from samples acquired manually and with the autosampler are functionally similar.

Association between toxic metals, vitamin D and preterm birth in the Maternal-Infant research on environmental chemicals study.

BACKGROUND: Toxic metals, like lead, are risk factors for preterm birth (PTB), but few studies have examined low levels found in most Canadians. Vitamin D, which may have antioxidant activity, protects against PTB. OBJECTIVES: In this study, we investigated the impact of toxic metals (lead, mercury, cadmium and arsenic) on PTB and examined if maternal plasma vitamin D concentrations modify these associations. METHODS: We investigated whether concentrations of metals in whole blood measured in early and late pregnancy were associated with PTB (<37 weeks) and spontaneous PTB in 1851 live births from the Maternal-Infant Research on Environmental Chemicals Study using discrete time survival analysis. We also investigated whether the risk of PTB was modified by first-trimester plasma 25-hydroxyvitamin D (25OHD) concentrations. RESULTS: Of 1851 live births, 6.1% (n = 113) were PTBs and 4.9% (n = 89) were spontaneous PTB. A 1 µg/dL increase in blood lead concentrations during pregnancy was associated with an increased risk of PTB (relative risk [RR] 1.48, 95% confidence interval [CI] 1.00, 2.20) and spontaneous PTB (RR 1.71, 95% CI 1.13, 2.60). The risk was higher in women with insufficient vitamin D concentrations (25OHD <50 nmol/L) for both PTB (RR 2.42, 95% CI 1.01, 5.79) and spontaneous PTB (RR 3.04, 95% CI 1.15, 8.04). However, an interaction on the additive scale was not present. Arsenic was associated with a higher risk of PTB (RR 1.10, 95% CI 1.02, 1.19) and spontaneous PTB (RR 1.11, 95% CI 1.03, 1.20) per 1 µg/L. CONCLUSIONS: Gestational exposure to low levels of lead and arsenic may increase the risk of PTB and spontaneous PTB; individuals with insufficient vitamin D may be more susceptible to the adverse effects of lead. Given our relatively small number of cases, we encourage testing of this hypothesis in other cohorts, especially those with vitamin D-deficient populations.

Leisure noise exposure and hearing outcomes among Canadians aged 6 to 79 years.

OBJECTIVE: To examine the association between individual and cumulative leisure noise exposure in addition to acceptable yearly exposure (AYE) and hearing outcomes among a nationally representative sample of Canadians. DESIGN: Audiometry, distortion-product otoacoustic emissions (DPOAEs) and in-person questionnaires were used to evaluate hearing and leisure noise exposure across age, sex, and household income/education level. High-risk cumulative leisure noise exposure was defined as 85 dBA or greater for 40 h or more per week, with AYE calculations also based on this occupational limit. STUDY SAMPLE: A randomised sample of 10,460 respondents, aged 6-79, completed questionnaires and hearing evaluations between 2012 and 2015. RESULTS: Among 50-79 year olds, high-risk cumulative leisure noise was associated with increased odds of a notch while high exposure to farming/construction equipment noise was associated with hearing loss, notches and absent DPOAEs. No associations with hearing loss were found however, non-significant tendencies observed included higher mean hearing thresholds, notches and hearing loss odds. CONCLUSION: Educational outreach and monitoring of hearing among young and middle-aged populations exposed to hazardous leisure noise would be beneficial.

A comparison of self-reported health status and perceptual responses toward environmental noise in rural, suburban, and urban regions in Canada.

Health Canada, in collaboration with Advanis, conducted the Canadian Perspectives on Environmental Noise Survey (CPENS) to investigate expectations and attitudes toward environmental noise in rural and non-rural Canada. The CPENS, a 26-item questionnaire, was completed online by 6647 randomly selected Canadians, age 18 y and older between April and May 2021. The prevalence of reporting their area as often or always calm, quiet, and relaxing was 76.8%, 64%, and 48.4% in rural/remote, suburban, and urban, respectively. A high expectation of quiet was less prevalent yet followed the same pattern: rural/remote (58.2%), suburban (37.4%), and urban (21.8%). Self-reported health status and noise sensitivity were unrelated to geographic region. A high magnitude of non-specific sleep disturbance over the previous 12 months was reported by 7.8% overall; highest among urban dwellers (9.8%), followed by suburban (7.2%) and rural/remote (5.5%) dwellers (p < 0.01). High annoyance toward road traffic noise was 8.5% overall, and significantly higher in urban (10.5%), relative to suburban (7.9%) and rural/remote (6.6%) areas (p < 0.0001). Annoyance toward noise from rail, aircraft, mining, industry, marine activity, construction, wind turbines, and landscaping equipment is reported. The analysis also explores potential differences between Indigenous Peoples of Canada and non-Indigenous Canadians in their attitudes and expectations toward environmental noise.

Impacts of Subway System Modifications on Air Quality in Subway Platforms and Trains.

Subway PM2.5 can be substantially sourced from the operation of the system itself. Improvements in subway air quality may be possible by examining the potential to reduce these emissions. To this end, PM2.5 was measured on the trains and station platforms of the Toronto subway system. A comparison with previously published data for this system reveals significant changes in below ground platform PM2.5. A reduction of nearly one-third (ratio (95% CI): 0.69 (0.63, 0.75)) in PM2.5 from 2011 to 2018 appears to have resulted from a complete modernization of the rolling stock on one subway line. In contrast, below ground platform PM2.5 for another line increased by a factor of 1.48 (95% CI; 1.42, 1.56). This increase may be related to an increase in emergency brake applications, the resolution of which coincided with a large decrease in PM2.5 concentrations on that line. Finally, platform PM2.5 in two newly opened stations attained, within one year of operation, typical concentrations of the neighboring platforms installed in 1963. Combined, these findings suggest that the production of platform PM2.5 is localized and hence largely freshly emitted. Further, PM2.5 changed across this subway system due to changes in its operation and rolling stock. Thus, similar interventions applied intentionally may prove to be equally effective in reducing PM2.5. Moreover, establishing a network of platform PM2.5 monitors is recommended to monitor ongoing improvements and identify impacts of future system changes on subway air quality. This would result in a better understanding of the relationship between the operations and air quality of subways.

Self-reported occupational noise exposure and cardiovascular disease in Canada: Results from the Canadian Health Measures Survey.

Self-reported occupational noise exposure has been associated with impaired hearing, but its relationship with extra-auditory affects remains uncertain. This research assessed the association between self-reported occupational noise exposure and cardiovascular outcomes. Participants (n = 6318, ∼50% male) from the Canadian Health Measures Survey (2012-2015) aged 20-79 years were randomly recruited across Canada. An in-person household interview included basic demographics, perceived stress, diagnosed health conditions, and self-reported exposure to a noisy work environment. Direct physiological assessment in a mobile examination centre permitted the determination of biomarkers/risk factors related to cardiovascular function. Logistic or linear regression models explored the association between self-reported occupational noise exposure and several cardiovascular endpoints after adjusting for confounding variables. After adjustments, there was no evidence for an association between occupational noise and any of the evaluated endpoints, which included but were not limited to blood pressure, heart rate, blood glucose, insulin, lipids, diagnosed hypertension, medication for hypertension, myocardial infarction, stroke, or heart disease. There was no evidence that self-reported occupational noise exposure was associated with evaluated cardiovascular-related biomarkers, or cardiovascular diseases among Canadians aged 20-79 years. This study, and others like it, provides an important contribution to an evidence base that could inform policy related to occupational noise exposure.

High frequency hearing impairment and cardiovascular disease in Canada: Results from the Canadian Health Measures Survey.

Noise-induced stress may precipitate cardiovascular diseases. This research assessed the association between sensorineural bilateral high frequency hearing loss (HFHL), as an indication of excessive noise exposure, and cardiovascular outcomes. Participants (n = 6318, ∼50% male) 20-79 years were recruited through the cross-sectional Canadian Health Measures Survey. Questionnaires included several demographic and health-related variables. Audiometry and blood/urine collection took place in a mobile examination centre. Average thresholds ≥25 dB averaged across 3, 4, and 6 kHz defined HFHL. Logistic or linear regression models explored associations between HFHL and cardiovascular-related risk factors/outcomes. Adjusted models indicated elevated diastolic blood pressure in respondents with normal hearing, X¯ = 72.52 (95% confidence interval: 71.85-73.18) compared to the group with bilateral HFHL, X¯ = 70.28 (95%CI: 69.13-71.43), p < 0.05. Average total cholesterol, high-density lipoprotein, low-density lipoprotein and apolipoprotein A1 were elevated in the normal hearing group (p < 0.05). Insulin, high-sensitivity C-reactive protein, and average resting heart rate were elevated in the group with bilateral HFHL, p < 0.05. A stratified analysis by sex- and age, or history of loud occupational noise exposure, did not change the overall results. Although some findings warrant further exploration, the overall analysis did not provide compelling evidence for an association between HFHL and cardiovascular-related biomarkers, or cardiovascular diseases among Canadians aged 20-79 years.

Personal listening device usage among Canadians and audiometric outcomes among 6-29 year olds.

OBJECTIVE: To describe personal listening device (PLD) usage and sociodemographic variables among a nationally representative sample of Canadians and examine audiometric outcomes among a subsample. DESIGN: Audiometry and in-person questionnaires were used to evaluate hearing and PLD usage across age, sex, household income/education level. PLD exposure was quantified using a common occupational noise limit. STUDY SAMPLE: A randomised sample of 10,460 respondents, aged 6-79, with audiometric analysis of a subsample (n = 4807), aged 6-29, tested between 2012 and 2015. RESULTS: Loud PLD usage was reported by19.5% of Canadians. The highest prevalence was among teenagers (44.2%) and young adults (36.3%). Among children, 13.1% of users listened at loud volumes. High PLD usage (equivalent to or above 85 dBA, LEX 40) among 12-19 year olds was double that of 20-29 year olds: 10.2% versus 5.1%E. Five years or more of loud PLD usage was associated with significantly higher mean hearing thresholds compared to less years. No association between loud or high PLD usage and mean thresholds were found. CONCLUSION: The majority used PLDs safely, however a small proportion reported high risk usage which will impact hearing should this pattern persist over many years.

Prevalence of loud leisure noise activities among a representative sample of Canadians aged 6-79 years.

This population-based study estimates the prevalence of loud leisure noise exposure and hearing protection usage among Canadians, as well as the population potentially at-risk using an occupational limit of 85 dBA, LEX 40 h, which denotes a typical occupational noise limit for a 40 hour work week. A total of 10 460 participants, aged 6-79 years, completed a Canadian Health Measures Survey household questionnaire. Loud leisure noise was defined by vocal effort required while communicating at arm's length except for loud personal listening device (PLD) usage with earbuds/headphones, which included both volume setting and vocal effort. The most prevalent loud leisure noise activities were amplified music, car/home stereo listening, and power tools, with 40% reporting each source, followed by sporting/entertainment (25%), gasoline engines (23%), and loud PLD listening (19.5%). Loud leisure noise was more prevalent among 12-39 year olds and males. Hearing protection usage was uncommon, from 44.2% (firearms) to 20.3% (power tools) and below 3% during amplified music and sporting/entertainment events. Calculations using self-reported duration of loud leisure noise activities estimated that 6.6 × 106 Canadians were in the high cumulative noise exposure category. A large proportion of Canadians would be expected to develop some degree of noise-induced hearing loss should this pattern persist over years.

Sodium bisulfite pyrosequencing revealed that developmental exposure to environmental contaminant mixtures does not affect DNA methylation of DNA repeats in Sprague-Dawley rats.

Hypomethylation of DNA repeats has been linked to diseases and cancer predisposition. Human studies suggest that higher blood concentrations of environmental contaminants (EC) correlate with levels of hypomethylation of DNA repeats in blood. The objective of this study was to examine the effect of in utero and/or lactational exposure to EC on the methylation of DNA repeats (LINE-1 and identifier element) in Sprague-Dawley rat pups at birth, at postnatal day (PND) 21, and in adulthood (PND78-86). From gestation day 0 to PND20, dams were exposed to a mixture "M" of polychlorinated biphenyls (PCB), pesticides, and methylmercury (MeHg), at 0.5 or 1 mg/kg/d (0.5M and M). At birth, some control (C) and M litters were cross-fostered to create the following in utero/postnatal exposure groups: C/C, M/C, C/M, M/M. Additional dams received 1.8 ng/kg/d of a mixture of aryl-hydrocarbon receptor (AhR) agonists (non-ortho-PCB, PC-dibenzodioxins, and PC-dibenzofurans) without or with 0.5M (0.5MAhR). Measurements of EC residue levels confirmed differences in their accumulation across treatments, age, and tissues. Although induction of hepatic detoxification enzyme activities (cytochrome P-450) demonstrated biological effects of treatments, the assessment of methylation in DNA repeats by sodium bisulfite pyrosequencing of liver, spleen, and thymus samples revealed no marked treatment-related effects but significant tissue- and age-related methylation differences. Further studies are required to determine whether absence of significant observable treatment effects on methylation of DNA repeats in the rat relate to tissue, strain, or species differences.

Estimating annoyance to calculated wind turbine shadow flicker is improved when variables associated with wind turbine noise exposure are considered.

The Community Noise and Health Study conducted by Health Canada included randomly selected participants aged 18-79 yrs (606 males, 632 females, response rate 78.9%), living between 0.25 and 11.22 km from operational wind turbines. Annoyance to wind turbine noise (WTN) and other features, including shadow flicker (SF) was assessed. The current analysis reports on the degree to which estimating high annoyance to wind turbine shadow flicker (HAWTSF) was improved when variables known to be related to WTN exposure were also considered. As SF exposure increased [calculated as maximum minutes per day (SFm)], HAWTSF increased from 3.8% at 0 ≤ SFm < 10 to 21.1% at SFm ≥ 30, p < 0.0001. For each unit increase in SFm the odds ratio was 2.02 [95% confidence interval: (1.68,2.43)]. Stepwise regression models for HAWTSF had a predictive strength of up to 53% with 10% attributed to SFm. Variables associated with HAWTSF included, but were not limited to, annoyance to other wind turbine-related features, concern for physical safety, and noise sensitivity. Reported dizziness was also retained in the final model at p = 0.0581. Study findings add to the growing science base in this area and may be helpful in identifying factors associated with community reactions to SF exposure from wind turbines.

Exposure to wind turbine noise: Perceptual responses and reported health effects.

Health Canada, in collaboration with Statistics Canada, and other external experts, conducted the Community Noise and Health Study to better understand the impacts of wind turbine noise (WTN) on health and well-being. A cross-sectional epidemiological study was carried out between May and September 2013 in southwestern Ontario and Prince Edward Island on 1238 randomly selected participants (606 males, 632 females) aged 18-79 years, living between 0.25 and 11.22 km from operational wind turbines. Calculated outdoor WTN levels at the dwelling reached 46 dBA. Response rate was 78.9% and did not significantly differ across sample strata. Self-reported health effects (e.g., migraines, tinnitus, dizziness, etc.), sleep disturbance, sleep disorders, quality of life, and perceived stress were not related to WTN levels. Visual and auditory perception of wind turbines as reported by respondents increased significantly with increasing WTN levels as did high annoyance toward several wind turbine features, including the following: noise, blinking lights, shadow flicker, visual impacts, and vibrations. Concern for physical safety and closing bedroom windows to reduce WTN during sleep also increased with increasing WTN levels. Other sample characteristics are discussed in relation to WTN levels. Beyond annoyance, results do not support an association between exposure to WTN up to 46 dBA and the evaluated health-related endpoints.

Personal and situational variables associated with wind turbine noise annoyance.

The possibility that wind turbine noise (WTN) affects human health remains controversial. The current analysis presents results related to WTN annoyance reported by randomly selected participants (606 males, 632 females), aged 18-79, living between 0.25 and 11.22 km from wind turbines. WTN levels reached 46 dB, and for each 5 dB increase in WTN levels, the odds of reporting to be either very or extremely (i.e., highly) annoyed increased by 2.60 [95% confidence interval: (1.92, 3.58), p < 0.0001]. Multiple regression models had R(2)'s up to 58%, with approximately 9% attributed to WTN level. Variables associated with WTN annoyance included, but were not limited to, other wind turbine-related annoyances, personal benefit, noise sensitivity, physical safety concerns, property ownership, and province. Annoyance was related to several reported measures of health and well-being, although these associations were statistically weak (R(2 )< 9%), independent of WTN levels, and not retained in multiple regression models. The role of community tolerance level as a complement and/or an alternative to multiple regression in predicting the prevalence of WTN annoyance is also provided. The analysis suggests that communities are between 11 and 26 dB less tolerant of WTN than of other transportation noise sources.

Self-reported and measured stress related responses associated with exposure to wind turbine noise.

The current study was the first to assess stress reactions associated with wind turbine noise (WTN) exposure using self-reported and objective measures. Randomly selected participants, aged 18-79 yr (606 males; 632 females), living between 0.25 and 11.22 km from wind turbines, were exposed to outdoor calculated WTN levels up to 46 dBA (response rate 78.9%). Multiple regression modeling left the great majority (77%-89%) of the variance in perceived stress scale (PSS) scores, hair cortisol concentrations, resting blood pressure, and heart rate unaccounted for, and WTN exposure had no apparent influence on any of these endpoints. PSS scores were positively, but weakly, related to cortisol concentrations and resting heart rate (Pearson r = 0.13 and r = 0.08, respectively). Across WTN categories, modeled mean PSS scores ranged from 13.15 to 13.84 (p = 0.8614). Modeled geometric means for hair cortisol concentrations, resting mean systolic, diastolic blood pressure, and heart rate were 150.54-191.12 ng/g (p = 0.5416), 113.38-116.82 mmHg (p = 0.4990), 67.98-70.34 mmHg (p = 0.5006), and 68.24-70.71 bpm (p = 0.5223), respectively. Irrespective of WTN levels, diastolic blood pressure appeared to be slightly (2.90 mmHg 95% CI: 0.75,5.05) higher among participants highly annoyed by blinking lights on turbines (p = 0.0081). Collectively, the findings do not support an association between exposure to WTN up to 46 dBA and elevated self-reported and objectively defined measures of stress.

An assessment of quality of life using the WHOQOL-BREF among participants living in the vicinity of wind turbines.

Living within the vicinity of wind turbines may have adverse impacts on health measures associated with quality of life (QOL). There are few studies in this area and inconsistent findings preclude definitive conclusions regarding the impact that exposure to wind turbine noise (WTN) may have on QOL. In the current study (officially titled the Community Noise and Health Study or CNHS), the World Health Organization QOL-BREF (WHOQOL-BREF) questionnaire provided an evaluation of QOL in relation to WTN levels among randomly selected participants aged 18-79 (606 males, 632 females) living between 0.25 and 11.22 km from wind turbines (response rate 78.9%). In the multiple regression analyses, WTN levels were not found to be related to scores on the Physical, Psychological, Social or Environment domains, or to rated QOL and Satisfaction with Health questions. However, some wind turbine-related variables were associated with scores on the WHOQOL-BREF, irrespective of WTN levels. Hearing wind turbines for less than one year (compared to not at all and greater than one year) was associated with improved (i.e. higher) scores on the Psychological domain (p=0.0108). Lower scores on both the Physical and Environment domains (p=0.0218 and p=0.0372, respectively), were observed among participants reporting high visual annoyance toward wind turbines. Personal benefit from having wind turbines in the area was related to higher scores on the Physical domain (p=0.0417). Other variables significantly related to one or more domains, included sex, age, marital status, employment, education, income, alcohol consumption, smoking status, chronic diseases and sleep disorders. Collectively, results do not support an association between exposure to WTN up to 46 dBA and QOL assessed using the WHOQOL-BREF questionnaire.

Audiometric thresholds and portable digital audio player user listening habits.

OBJECTIVE: To examine the relationship between portable digital audio player listening behaviours and (1) measured sound pressure levels, (2) audiometric measures, (3) self-reported hearing loss symptoms. DESIGN: A questionnaire to evaluate listening behaviours, including self-reported hearing loss symptoms and listening duration/volume settings. Multivariate regression analysis was used to determine the relationship between these variables, audiometric evaluation, calculated exposure levels, Lex(8hr), and measured sound pressure levels, Leq(32sec). STUDY SAMPLE: This study included 103 males and 134 female subjects aged 10 to 17 years. RESULTS: Calculated Lex(8hr) and measured Leq(32sec) levels increased with age and self-reported usage time. Audiometric thresholds averaged over 4 and 8 kHz were higher when usage exceeded five years as compared to less than one year. Higher measured sound pressure levels were associated with worse audiometric thresholds at (0.5, 1, 2 kHz, averaged) and 4 kHz. Self-reported hearing loss symptoms were reported by 33% to 50% of subjects. CONCLUSIONS: In this cohort sample, our results support a statistical association between hearing acuity and (1) Self-reported weekly usage in hours; (2) Tightness of fit; (3) Years of usage; and (4) Measured sound pressure levels. Generalizing these results beyond the current sample would require additional research.

Variation in the stringency of COVID-19 public health measures on self-reported health, stress, and overall wellbeing in Canada.

Evidence is building regarding the association between government implemented public health measures aimed at combating COVID-19 and their impacts on health. This study investigated the relationship between the stringency of public health measures implemented in Canada and self-reported mental health, physical health, stress, and wellbeing among a random sample of 6647 Canadians 18 years of age and older. The analysis was based on self-reported health data from the Canadian Perspectives on Environmental Noise Survey. This data was combined with the Oxford COVID-19 Government Response Tracker database, which included overall stringency index (SI), and four of its sub-components, i.e., school and business closures, restrictions on gatherings, and stay at home policies. Adjusted multivariate logistic regression models indicated that the magnitude of the overall SI was associated with higher or lower odds of reporting worse physical health, mental health, stress and/or overall wellbeing, depending on the measure evaluated. Similarly, policy directed at the four sub-components had varying impacts on the odds of reporting worse health, depending on the sub-component, the strength of the policy restriction, and the health outcome evaluated. The association between the strength of the public health measures and self-reported health, and how this may inform future policy, is discussed.

Biomonitoring of DEET and DCBA in Canadian children following typical protective insect repellent use.

N,N-diethyl-m-toluamide (DEET) is an ingredient found in many consumer insect repellents and its use is recommended to Canadians by government agencies, including Health Canada, for protection against insect bites including mosquitos and ticks. The majority of research on DEET exposure and toxicokinetics in humans has focused on adult populations with little information from vulnerable populations, including children. We aimed to fill this knowledge gap by examining real-world exposure data for DEET and its metabolite 3-diethylcarbamoyl benzoic acid (DCBA) in a sample population of Canadian children. We conducted a 24-h observational exposure human biomonitoring study at three overnight summer camps in Ontario, Canada through July and August 2019. Participating children aged 7-13 years provided multiple spot urine samples over a 24-h period and completed a journal to document insect repellent use and factors that could influence absorption of DEET. Children were instructed to use insect repellent as they usually would while attending a summer camp. Exposure was quantified using the information from the participant's journal and the change in the mass of their insect repellent containers over the course of the study. A total of 389 urine samples were collected from 124 children. Among participants using insect repellent, urinary levels of DEET were elevated between 2 and 8 h post-application and decreased thereafter but remained qualitatively higher than concentrations in participants who did not use insect repellent on the study day, even at 18-22 h post-application. DCBA was the predominant metabolite of DEET exposure in urine. DCBA was elevated between 8 and 14 h post-application, and declined thereafter, but not to the level observed among those who did not use insect repellent on the study day. Children who used more insect repellent, or used higher concentration insect repellent (10%-30% DEET) excreted higher levels of DEET and DCBA. Excreted DEET and DCBA accounted for 0.001% (median) and 1.3% (median) of the estimated applied DEET, respectively. Children did not reach an undetectable level of DEET or DCBA in urine, even among those not using insect repellent during the study day, indicating a potentially complex multi-route exposure to insect repellents in a real world scenario. This work provides targeted biomonitoring data for children intentionally using DEET-based insect repellents for normal protective use, and will support the risk re-evaluation of DEET by Health Canada.

Audiometric thresholds among a Canadian sample of 10 to 17 year old students.

A total of 237 students, 10 to 17 years of age, from 14 schools underwent hearing evaluations. Otoscopic examination, tympanometry and air-conduction pure tone audiometry was conducted at low (0.5, 1, 2 kHz) and high (4 and 8 kHz) frequencies. In all schools, hearing thresholds were measured with headphones in a portable audiometric booth. Socio-demographic information from students and their parents were collected using questionnaires. Overall, the prevalence of any hearing loss greater than 15 dB was 22.3% for low or high frequency pure tone averages. Self-reported symptoms of hearing loss, such as tinnitus, difficulty following a conversation with background noise, and having to turn up the TV/radio more than in the past, were associated with audiometric thresholds, most notably at 4 kHz. These study findings are among the first to provide a detailed characterization of hearing status in a sample of youth in a Canadian demographic.