Uric acid and gamma-glutamyl-transferase in children and adolescents with obesity: Association to anthropometric measures and cardiometabolic risk markers depending on pubertal stage, sex, degree of weight loss and type of patient care: Evaluation of the adiposity patient follow-up registry

OBJECTIVES

Associations between body mass index (BMI)- standard deviation score (SDS)/waist-to-height ratio (WHtR) were studied with (i) serum uric acid (sUA)/gamma-glutamyl-transferase (GGT) and (ii) cardiometabolic risk markers in children with obesity, considering sex, pubertal development, and degree of weight loss/type of patient care.

METHODS

102 936 children from the Adiposity-Follow-up registry (APV; 47% boys) were included. Associations were analysed between sUA/GGT and anthropometrics, transaminases, lipids, fasting insulin (FI), homeostasis model assessment of insulin resistance (HOMA-IR), triglycerides to HDL-cholesterol (TG/HDL)-ratio. Follow-up analyses (3-24 months after baseline) considered a BMI-SDS reduction ≥0.2 (n = 11 096) or ≥0.5 (n = 3728). Partialized correlation analyses for sex and BMI-SDS were performed, taking pubertal development into consideration.

RESULTS

At baseline, BMI-SDS showed the strongest correlations to sUA (r = 0.35; n = 26 529), HOMA-IR/FI (r = 0.30; n = 5513 /n = 5880), TG/HDL-ratio (r = 0.23; n = 24 501), and WHtR to sUA (r = 0.32; n = 10 805), GGT (r = 0.34; n = 11 862) and Alanine-aminotransferase (ALAT) (r = 0.33; n = 11 821), with stronger correlations in boys (WHtR and GGT: r = 0.36, n = 5793) and prepubertal children (r = 0.36; n = 2216). GGT and sUA (after partializing effects of age, sex, BMI-SDS) showed a correlation to TG/HDL-ratio (r = 0.27; n = 24 501). Following a BMI-SDS reduction ≥0.2 or ≥0.5, GGT was most strongly related to Aspartate-aminotransferase (ASAT)/ ALAT, most evident in prepuberty and with increasing weight loss, and also to TG/HDL-ratio (r = 0.22; n = 1528). Prepubertal children showed strongest correlations between BMI-SDS/WHtR and GGT. ΔBMI-SDS was strongly correlated to ΔsUA (r = 0.30; n = 4160) and ΔGGT (r = 0.28; n = 3562), and ΔWHtR to ΔGGT (r = 0.28; n = 3562) (all p < 0.0001).

CONCLUSION

Abdominal obesity may trigger hyperuricemia and hepatic involvement already in prepuberty. This may be stronger in infancy than anticipated to date. Even moderate weight loss has favourable effects on cardiometabolic risk profile and glucose homeostasis.

Diabetic ketoacidosis in pediatric patients with type 1- and type 2 diabetes during the COVID-19 pandemic

BACKGROUND

COVID-19 pandemic caused families to stay home and cancel everyday activities. Hospital admissions decreased, affecting changes in diagnoses and management of chronic disease in children.

AIMS

We analyzed how the first lockdown influenced clinical presentation and manifestation of children with diabetes mellitus (DM) in a German University Hospital.

METHODS

During March 15th and October 11th 2020, data on general patient information, clinical symptoms and on lab results related to diabetic ketoacidosis (DKA) were analyzed in children (0-18 years) who presented with new onset of DM or poor metabolic control of known DM. All data including frequency and severity of DKA were compared to data from patients who presented in 2019.

RESULTS

Data from 125 participants with DM were evaluated (2020: n = 52; 2019: n = 73). In 2020, twelve patients (23.1%) were diagnosed with new onset DM, two of them with type2 diabetes, and 66.7% presented with DKA including both patients T2DM. In 2019, 24.5% of patients had new onset DM, and 50% of them presented with DKA. In 2020, patients with new onset DM were younger, presented with more severe symptoms of DKA and had to stay longer in hospital compared to 2019. In 2020, six children (50%) with new onset DM were <6 years, whereas in 2019 most children with new onset DM were adolescents (n = 7, 38.9%).

CONCLUSION

COVID-19 lockdown aggravated complications of diabetes onset and therapy management, including severity and frequency of DKA. It underlines the need of health education for early DKA diagnosis to early identify children at risk.

Childhood Obesity and Cancer Risk in Adulthood

PURPOSE OF REVIEW

The purpose of this review is to summarize our current understanding of the association between childhood obesity and cancer risk later in life.

RECENT FINDINGS

Adipose tissue secrets a variety of adipocytokines, and expression and/or secretion rate of most of them seems to be increased or dysregulated in obesity. In addition, obesity leads to increased secretion of proinflammatory cytokines such as interferon-γ (IFN-γ), interleukin 6 (IL-6), and tumor necrosis factor-α (TNF-α), which promotes an infiltration of inflammatory immune cells into adipose tissue. This process may facilitate a state of "subclinical inflammation" (metaflammation) and may lead to the development of the metabolic syndrome (MetS), starting as early as during childhood. In addition, several oncogenes have been linked to inflammation and cancer development via different pathways, and several types of tumors need an inflammatory environment before a malignant change occurs. An inflammatory environment seems to promote the proliferation and survival of malignant cells as well as angiogenesis. Natural killer (NK) cells play an important role in this process, as they are able to kill transformed cells without prior sensitization and coordinate subsequent immune responses by producing distinct cytokines, thus providing antitumor immunity. First studies in children have suggested that NK cells from obese children are activated, metabolically stressed, and functionally deficient. This may lead to a suppression of antitumor immunity as early as during childhood, probably many years before the development of cancer. Epidemiological studies have shown a strong association between higher body mass index (BMI) during childhood and adolescence and increased risk for several malignancies in adulthood, including leukemia, Hodgkin's disease, colorectal cancer, and breast cancer. Underlying mechanisms are not completely understood, but several adipocytokines and inflammatory markers including NK cells seem to be "key players" in this process.

Metabolic Syndrome in Children and Adolescents: Diagnostic Criteria, Therapeutic Options and Perspectives

PURPOSE OF REVIEW

This review summarizes our current understanding of the metabolic syndrome (MetS) in children and adolescents. Special emphasis is given towards diagnostic criteria and therapeutic options.

RECENT FINDINGS

Consistent diagnostic criteria to define MetS in childhood and adolescence are not available to date. There is common agreement that the main features defining MetS include (1) disturbed glucose metabolism, (2) arterial hypertension, (3) dyslipidemia, and (4) abdominal obesity. However, settings of cut-off values are still heterogeneous in the pediatric population. Additional features that may define cardiometabolic risk, such as non-alcoholic fatty liver disease (NAFDL) or hyperuricemia, are not considered to date. Prevalence of childhood obesity has more than doubled since 1980, and 6-39% of obese children and adolescents already present with MetS, depending on the definition applied. There is common agreement that a consistent definition of MetS is urgently needed for children to identify those at risk as early as possible. Such definition criteria should consider age, gender, pubertal stage, or ethnicity. Additional features such as NAFDL or hyperuricemia should also be included in MetS criteria. Lifestyle modification is still the main basis to prevent or treat childhood obesity and MetS, as other therapeutic options (pharmacotherapy, bariatric surgery) are not available or not recommended for the majority of affected youngster.

Dietary risk factors for inflammatory bowel diseases in a high-risk population: Results from the Faroese IBD study

Background

The Faroe Islands currently have the highest recorded inflammatory bowel disease (IBD) incidence in the world.

Objective

This study investigated environmental risk factors for IBD in the Faroese population.

Methods

Environmental exposure data including lifestyle risk factors and neurotoxicants collected for over 30 years were retrieved from the Children's Health and the Environment in the Faroes (CHEF) cohorts including mainly mother–child pairs, with exposure data collected from pregnant mothers. For lifestyle risk factors, the incidence of IBD and ulcerative colitis (UC) was calculated as the rate ratio (RR) with 95% confidence intervals (CI) in exposed versus non-exposed persons. For neurotoxicants RR was calculated for persons with high versus low exposure.

Results

Six cohorts included 5698 persons with complete follow-up data and at least one exposure, and 37 were diagnosed with IBD. For pilot whale/blubber, the RR was 1.02 (95% CI, 0.48–2.18); RR of 1.01 for fish (95% CI, 0.35–2.91); and of the pollutants studied, a statistical significantly increased risk was found for 1,1,1,-trichloro-2,2-bis-(p-chlorophenyl) ethane (p,p'-DDT); RR 3.04 (95% CI, 1.12–8.30). RRs were 1.96 (95% CI, 1.03–3.73) for smoking and 1.10 (95% CI, 0.55–2.19) for alcohol intake.

Conclusion

The high IBD incidence is unlikely to be caused by special dietary habits or by environmental pollutants.

Future directions for monitoring and human health research for the Arctic Monitoring and Assessment Programme

For the last two and a half decades, a network of human health experts under the Arctic Monitoring and Assessment Program (AMAP) has produced several human health assessment reports. These reports have provided a base of scientific knowledge regarding environmental contaminants and their impact on human health in the Arctic. These reports provide scientific information and policy-relevant recommendations to Arctic governments. They also support international agreements such as the Stockholm Convention on Persistent Organic Pollutants (POPs) and the Minamata Convention on Mercury. Key topics discussed in this paper regarding future human health research in the circumpolar Arctic are continued contaminant biomonitoring, health effects research and risk communication. The objective of this paper is to describe knowledge gaps and future priorities for these fields.

Football training improves metabolic and cardiovascular health status in 55- to 70-year-old women and men with prediabetes

We examined the effects of 16 weeks of football training and dietary advice on blood glucose control and health status in 55- to 70-year-old women and men with prediabetes. Fifty participants with prediabetes (age; 61 ± 6 years, BMI; 29.6 ± 4.7; VO_2max 22.3 ± 5.7 mL·min^-1 ·kg^-1 ) were randomized into a football and dietary advice group (F+D; n = 27) and a dietary advice group (D; n = 23). F+D performed football training (twice weekly 30- to 60-minutes sessions) and received dietary advice, while D only received dietary advice. An oral glucose tolerance test (OGTT) was completed pre and post the 16-week period. Body composition, blood pressure, and maximal oxygen uptake (VO_2max ) were additionally measured. Both groups demonstrated a decrement (P < .05) in fasting blood glucose (-0.4 ± 0.5 mmol·L^-1 ) and lowered blood glucose throughout OGTT. F+D displayed lower values than D (P < .05) after 60 minutes (9.0 ± 2.7 vs 10.6 ± 2.9 mmol·L^-1 ) and 120 minutes (5.7 ± 1.6 vs 7.5 ± 2.4 mmol·L^-1 ). VO_2max increased by 14% in F+D, with a higher (P < .05) change score than in D (2%). Mean arterial pressure declined more (P < .05) in F+D than in D (-8 ± 9 vs -4 ± 11 mm Hg). Fat loss was greater (P < .05) in F+D than in D (-3.4 ± 2.8 vs -1.2 ± 2.0 kg), and the increase in lean body mass was also greater (P < .05) in F+D than in D (0.7 ± 1.5 vs -0.3 ± 1.6 kg). In conclusion, football training combined with dietary advice has broad-spectrum effects on metabolic and cardiovascular health profile with greater overall effects than professional dietary advice per se for 55- to 70-year-old women and men with prediabetes.

Physiological reactions to long-term fishing in the Barents Sea

Background

Fishing in distant waters for months may induce physiological stress.

Aims

To assess the physiological stress reactions in fishermen working for 2-3 months continuously in 6-h shifts on trawlers in the Barents Sea.

Methods

The crew of five trawlers fishing in the Barents Sea from January to April 2004 were invited to participate. In the week before and 5-7 days after the trip, the following measures were collected: salivary cortisol four times a day, 24-h urinary cortisol, blood pressure, heart rate, serum cholesterol, serum high-density lipoprotein (HDL-cholesterol), HbA1c (glycosylated haemoglobin) and weight. In addition, 24-h urinary cortisol, blood pressure and heart rate were measured three times. A questionnaire on health, social conditions and work environment was obtained after the trip.

Results

In total, 136 men agreed to participate. Full data were obtained for 96 fishermen (70%). A significant decrease in salivary and urinary cortisol was found during the trip. Adjustment for age, body mass index, smoking, shift work schedule and time of day for sample collection did not change this finding. Systolic and diastolic blood pressure declined significantly and remained significantly lower after the trip compared to before the trip. Serum cholesterol/HDL ratio declined significantly, whereas triglycerides, HbA1c and weight were unchanged.

Conclusions

Working up to 3 months on 6-h shifts, 84 h a week, with moderate physical activity, even in artificial light and cold weather on a ship, did not result in increased physiological stress.

Inflammatory bowel diseases in Faroese-born Danish residents and their offspring: further evidence of the dominant role of environmental factors in IBD development

BACKGROUND

The incidence of inflammatory bowel disease (IBD) is record high in the Faroe Islands, and many Faroese emigrate to Denmark, where the IBD incidence is considerably lower.

AIM

To study the IBD incidence in first-, second- and third-generation immigrants from the Faroe Islands to Denmark to assess the extent to which the immigrants adopt the lower IBD incidence of their new home country.

METHODS

Data on Faroese-born Danish residents and their children were retrieved from the Danish Central Population Register for 1980-2014. Incident IBD cases were identified from the Danish National Patient Register. Standardised Incidence Ratios (SIRs) were used to compare the IBD risk in immigrants with that of Danes. 95% confidence intervals (CI) were calculated using the square-root transform.

RESULTS

First-generation Faroese immigrants had a higher IBD incidence than Danes, SIR 1.25 (95% CI, 0.97-1.59) for men and 1.28 (95% CI, 1.05-1.53) for women. This excess risk derived from ulcerative colitis (UC), SIR 1.44 (95% CI, 1.10-1.87) for men and 1.36 (95% CI, 1.09-1.68) for women. No excess risk was found for Crohn's disease (CD). The UC risk was nearly doubled during the immigrants' first 10 years in Denmark; SIR 2.13 (95% CI, 1.52-2.92) for men and 1.63 (95% CI, 1.19-2.18) for women.

CONCLUSIONS

Although some impact of genetic dilution cannot be excluded, our findings indicate importance of gene-environment interplay in UC, as the excess UC risk in Faroese immigrants to Denmark disappeared over time and over one generation in men and over two generations in women.

Broad-spectrum health improvements with one year of soccer training in inactive mildly hypertensive middle-aged women

The study tested the hypothesis that long-term soccer training has positive impact on cardiovascular profile, body composition, bone health, and physical capacity in inactive, pre-menopausal women with mild hypertension. The study applied a randomized controlled design in which physically inactive middle-aged women were separated into a soccer training group (n=19; SOC) and a control group (n=12; CON). SOC performed 128±29 (±SD) one-h small-sided soccer training sessions over one year. Blood pressure, body composition, blood lipid profile, and fitness level were determined pre- and post-intervention. Over one year, mean arterial pressure decreased more in SOC than in CON (-5±7 vs +4±5 mmHg; P<.05). Total-body fat mass decreased more (P<.05) in SOC than in CON (-2.5±2.5 vs +0.6±3.2 kg; P<.05), while the change scores for lean body mass were not significantly different in SOC (2.6±2.7 kg) compared to CON (1.1±1.9 kg, P=.09). Over one year, change scores in whole-body bone mineral density (0.004±0.032 vs -0.019±0.026 g·cm² ) as well as bone mineral content (30±70 vs -39±113 g) were positive in SOC compared to CON (P<.05). Post-intervention plasma triglycerides decreased more (-0.1±0.7 vs +0.2±0.2 mmol·L^-1 ) and HDL cholesterol increased more (0.2±0.7 vs -0.2±0.2 mmol·L^-1 ) in SOC than in CON (P<.05). Yo-Yo intermittent endurance level 1 (122±105 vs 2±21%) and 20-m sprint performance (6±6 vs -1±2%) increased more (P<.05) in SOC than in CON. In conclusion, long-term soccer training resulted in broad-spectrum improvements in the health profile of untrained, pre-menopausal women with mild hypertension, including cardiovascular, metabolic, and musculo-skeletal benefits.

Children's white blood cell counts in relation to developmental exposures to methylmercury and persistent organic pollutants

BACKGROUND

To explore possible markers of developmental immunotoxicity, we prospectively examined 56 children to determine associations between exposures to methylmercury and persistent organic pollutants since birth and the comprehensive differential counts of white blood cells (WBC) at age 5 years.

MATERIALS AND METHODS

Extended differential count included: neutrophils, eosinophils, basophils, lymphocytes (includingT cells, NK cells, and B cells), and monocytes. Organochlorine compounds (OCs) including polychlorinated biphenyls (PCBs) and pesticides, five perfluoroalkyl substances (PFASs), and total mercury (Hg) were measured in maternal (n=56) and children's blood at 18 months (n=42) and 5 years (n=54). We constructed latent functions for exposures at three different ages using factor analyses and applied structural equation models adjusted for covariates.

RESULTS

Prenatal mercury exposure was associated with depleted total WBC, especially for lymphocytes, where a one standard deviation (SD) increase in the exposure was associated with a decrease by 23% SD (95% CI: -43, -4) in the cell count. Prenatal exposure to OCs was marginally associated with decreases in neutrophil counts. In contrast, the 5-year PFASs concentrations were associated with higher basophil counts (B=46% SD, 95% CI: 13, 79). Significantly reduced subpopulations of lymphocytes such as B cells, CD4-positive T helper cells and CD4 positive recent thymic emigrants may suggest cellular immunity effects and dysregulation of T-cell mediated immunity.

CONCLUSION

Developmental exposure to environmental immunotoxicants appears to have different impacts on WBC counts in childhood.

Spermatogenic capacity in fertile men with elevated exposure to polychlorinated biphenyls

BACKGROUND

Endocrine disrupting industrial chemicals, such as polychlorinated biphenyls (PCBs), are suspected to adversely affect male reproductive functions.

OBJECTIVES

The Faroe Islands community exhibits an unusually wide range of exposures to dietary contaminants, and in this setting we examined the possible association between PCB exposure and semen quality and reproductive hormones in fertile Faroese men.

METHODS

Participants in this cross-sectional study include 266 proven fertile men residing in the Faroe Islands. PCB levels and hormone profiles were measured in serum samples taken at the clinical examination that included semen quality parameters.

RESULTS

A significant positive association was seen between serum-PCB and the testosterone/estradiol ratio (p=0.04). In the unadjusted analyses, elevated PCB exposure was associated with increased serum concentrations of SHBG (p=0.01) and FSH (p=0.05). We found no association between the serum PCB concentration and the semen quality variables.

CONCLUSION

In this population of highly exposed fertile men, the current serum-PCB concentration was associated with higher androgen/estrogen ratio. Further studies are needed to establish the findings and further document PCB-associated hormonal effects, any time windows of increased susceptibility, and the role of PCB in sub-fecundity.

Football training improves cardiovascular health profile in sedentary, premenopausal hypertensive women

The present study examined the effects of short-term recreational football training on blood pressure (BP), fat mass, and fitness in sedentary, 35-50-year-old premenopausal women with mild hypertension. Forty-one untrained, hypertensive women were randomized into a football training group (n = 21; FTG) and a control group (n = 20; CON). FTG performed 45 ± 1 1-h small-sided football training sessions during the 15-week intervention period. BP, body composition (dual-energy x-ray absorptiometry), blood lipid profile, and fitness level were determined pre- and post-intervention. After 15 weeks, systolic and diastolic BP, respectively, were lowered more (P < 0.05) in FTG (-12 ± 3 and -6 ± 2 mmHg) than in CON (-1 ± 1 and 1 ± 2 mmHg). Total body fat mass decreased more (P < 0.05) in FTG than in CON during the 15-week intervention period (-2.3 ± 0.5 kg vs 0.4 ± 0.3 kg). After 15 weeks, both total cholesterol (-0.4 ± 0.1 mmol/L vs 0.1 ± 0.2 mmol/L) and triglyceride (-0.2 ± 0.1 mmol/L vs 0.3 ± 0.2 mmol/L) were lowered more (P < 0.05) in FTG than in CON. Yo-Yo intermittent endurance level 1 test performance increased more (P < 0.05) in FTG than in CON (111 ± 18% vs 1 ± 3%) during the 15-week intervention period. In conclusion, short-term football training resulted in a marked reduction in BP and induced multiple improvements in fitness and cardiovascular health profile of untrained, premenopausal women with mild hypertension.

Exposure to persistent organic pollutants and sperm sex chromosome ratio in men from the Faroe Islands

People in the Arctic as well as fishermen on the polluted Swedish east coast are highly exposed to persistent organic pollutants (POPs). These compounds have been shown to affect the sperm Y:X chromosome ratio. In present study, the aim was to investigate whether polychlorinated biphenyl (PCB) congeners and 1,1,-dichloro-2,2,-bis(p-chlorophenyl)ethane (p,p'-DDE) influence sperm sex chromosome ratio in Faroese men, and whether these men differ regarding Y:X ratio compared to Greenland Inuit and Swedish fishermen. The study population (n=449) consisted of young men from the general population (n=276) as well as proven fertile men (n=173). The Y:X ratio was assessed by fluorescent in situ hybridization. Serum concentrations of POPs were measured using gas chromatography. Associations between POP concentrations and Y:X ratio were calculated using linear and non-linear regression models as well as trend analysis and pairwise comparison of exposure data categorized into quartiles. The selected POPs were associated with Y:X ratio in fertile Faroese men, but not in the total population; p,p'-DDE (95% CI for B=-0.005 to -0.001, p=0.005) and ΣPCB (95% CI for B=-0.005 to -0.001, p=0.012). Since p,p'-DDE and ΣPCB correlated significantly (r=0.927, p<0.001), the results involving the exposure variables can be regarded as a single finding. The Y:X ratio for the total Faroese population was 0.500±0.018, which was statistically significantly lower than in both Inuit and Swedish fishermen (0.512 for both). In conclusion, Faroese men presented with lower Y:X ratio than Greenland Inuit and Swedish fishermen. Although no direct health effects are expected due to the lower Faroese Y:X ratio, it could be indicative of adverse effects on the reproductive system.

Prevalence and incidence of Parkinson's disease in The Faroe Islands

OBJECTIVE

A study in The Faroe Islands in 1995 suggested a high prevalence of idiopathic Parkinson's disease (IPD) and total parkinsonism of 187.6 and 233.4 per 100,000 inhabitants respectively.

METHODS

Detailed case-finding methods 10 years later were used and a neurologist has verified the diagnosis.

RESULTS

The crude prevalence of IPD and total parkinsonism was 206.7 per 100,000 and 227.4 per 100,000 respectively. The age-adjusted prevalence is twice as high as data from Norway and Denmark. Age at initiation of treatment and the fatality rate did not explain the increased prevalence. During 1995-2005, the average annual incidence was 21.1 per 100,000 persons for Parkinson's disease, and 22.9 per 100,000 persons, if including atypical parkinsonism.

CONCLUSION

The high prevalence was verified and linked to a high incidence. The cause of the high prevalence is unknown, but neurotoxic contaminants in traditional food may play a role in the pathogenesis in this population, perhaps jointly with genetic predisposition.

Birthweight in a fishing community: significance of essential fatty acids and marine food contaminants

BACKGROUND

Marine food provides essential fatty acids that are important during pregnancy, but the benefits may be limited at high intakes and by seafood contaminants.

METHODS

In the fishing community of the Faroe Islands, 182 pregnant women with spontaneous singleton births were consecutively recruited for a cohort in 1994- 1995. Concentrations of fatty acids and seafood contaminants in blood samples were analysed as predictors of gestational length and birthweight.

RESULTS

Serum concentrations of eicosapentaenoic acid (EPA) increased with maternal marine food intake, while the tendency was less clear for docosahexaenoic acid (DHA). An increase in the relative concentration of DHA in cord serum phospholipids by 1% was associated with an increased duration of gestation by 1.5 days (95% CI : 0.7-2.2). However, birthweight adjusted for gestational length decreased by 246 g (95% CI : 16-476) for each increase by 1% of the EPA concentration in cord serum. Concentrations of the seafood pollutants mercury and polychlorinated biphenyls (PCB) were associated with fatty acids levels, but the contaminants did not appear to affect any of the outcome parameters.

CONCLUSION

An increased intake of marine fats appears to prolong the duration of gestation, but birthweight adjusted for gestational age may decrease at high intake levels. This effect does not seem to be due to increased exposures to seafood contaminants.

Neurobehavioral deficits associated with PCB in 7-year-old children prenatally exposed to seafood neurotoxicants

Prenatal exposure to polychlorinated biphenyls (PCBs) was examined by analysis of cord tissue from 435 children from a Faroese birth cohort. Analysis of 50 paired cord blood samples showed excellent correlation with the cord tissue concentration (r=.90). Among 17 neuropsychological outcomes determined at age 7 years, the cord PCB concentration was associated with deficits on the Boston Naming Test (without cues, two-tailed P=.09 not adjusted for mercury; with cues, P=.03), the Continuous Performance Test reaction time (P=.03), and, possibly, on long-term recall on the California Verbal Learning Test (P=.15). The association between cord PCB and cord-blood mercury (r=.42) suggested possible confounding. While no PCB effects were apparent in children with low mercury exposure, PCB-associated deficits within the highest tertile of mercury exposure indicated a possible interaction between the two neurotoxicants. PCB-associated increased thresholds were seen at two of eight frequencies on audiometry, but only on the left side, and no deficits occurred on evoked potentials or contrast sensitivity. The limited PCB-related neurotoxicity in this cohort appears to be affected by concomitant methylmercury exposure.

Impact of contrast sensitivity performance on visually presented neurobehavioral tests in mercury-exposed children

Presentation of neuropsychological tests on a computer screen may involve a visual challenge to the examinee. The possible need for adjustment for visual contrast sensitivity on test performance was therefore determined from data on 917 mercury-exposed children who were examined at age 7 years. Contrast sensitivity was found to be associated with performance on the computer-assisted Continuous Performance Test. However, it showed similar associations with performance on traditional pencil-and-paper tests, especially Bender Visual Motor Gestalt Test and Wechsler Intelligence Scale for Children-Revised (WISC-R) Block Designs. Contrast sensitivity was not associated with prenatal mercury exposure, and adjustment for visual function had only a negligible effect on the regression coefficients for mercury as predictor of neuropsychological deficits. The mercury-associated neurobehavioral deficits are therefore unlikely to be due to mercury-induced visual system dysfunction causing secondary deficits in cognitive domain testing. Visuospatial processing appears to be a determinant in contrast sensitivity performance, and careful consideration of whether to control for contrast sensitivity in future studies of neurotoxicant effects is therefore recommended.

Maternal seafood diet, methylmercury exposure, and neonatal neurologic function

OBJECTIVE

To determine whether neonatal neurologic function is adversely affected by seafood contaminants from maternal diet during pregnancy.

STUDY DESIGN

One hundred eighty-two singleton term births were evaluated in the Faeroe Islands, where marine food includes pilot whale. Maternal serum, hair, and milk and umbilical cord blood were analyzed for contaminants. Levels of essential fatty acids, selenium, and thyroid hormones were determined in cord blood. Each infant's neurologic optimality score was determined at 2 weeks of age adjusted for gestational age, and predictors were assessed by regression analysis.

RESULTS

Exposures to methylmercury and polychlorinated biphenyls were increased in relation to maternal seafood intake, as were omega3 fatty acid concentrations in cord serum. Thyroid function was normal. After adjustment for confounders, a 10-fold increase of the cord-blood mercury concentration was associated with a decreased neurologic optimality score of 2.0 (P =. 03). This effect corresponds to a decrease in gestational age of about 3 weeks. Other indicators of the seafood diet had no effect on this outcome.

CONCLUSIONS

Prenatal exposure to methylmercury from contaminated seafood was associated with an increased risk of neurodevelopmental deficit. Thus in this North Atlantic population, methylmercury constituted an important neurologic risk factor, although effects of other seafood components were not detectable.

Benchmark dose calculations of methylmercury-associated neurobehavioural deficits

Prenatal methylmercury exposure is associated with neuropsychological deficits in Faroese children at age 7 years. Lower confidence bounds of benchmark doses (BMDLs) have now been calculated. With the cord-blood mercury concentration as the dose parameter, a logarithmic dose-response model tended to show a better fit than a linear dose model for the attention, language and verbal memory tests. The lowest BMDLs averaged approximately 5 microgram/l cord blood, which corresponds to a maternal hair concentration of approximately 1 microgram/g. However, most BMDLs for hair mercury concentrations were higher. Thus, the results of the benchmark calculations depend on the assumed dose-response model.

Methylmercury exposure biomarkers as indicators of neurotoxicity in children aged 7 years

The mercury concentration in blood or scalp hair has been widely used as a biomarker for methylmercury exposure. Because of the increased risks associated with exposures during prenatal and early postnatal development, biomarker results must be interpreted with regard to the age-dependent susceptibility. The authors compared regression coefficients for five sets of exposure biomarkers in 917 children from the Faroe Islands examined at birth, 1 year, and 7 years. Outcome variables were the results of neuropsychologic examination carried out in 1993-1994 at age 7 years. After adjustment for covariates, the cord-blood concentration showed the clearest associations with deficits in language, attention, and memory. Fine-motor function deficits were particularly associated with the maternal hair mercury at parturition. Mercury concentrations in the child's blood and hair at age 7 years were significant predictors only of performance on memory for visuospatial information. These findings emphasize the usefulness of the cord-blood mercury concentration as a main risk indicator. They also support the notion that the greatest susceptibility to methylmercury neurotoxicity occurs during late gestation, while early postnatal vulnerability is less, and they suggest that the time-dependent susceptibility may vary for different brain functions.

Evoked potentials in Faroese children prenatally exposed to methylmercury

A study of 7-year-old children from a fishing village on Madeira has suggested that latencies of evoked potentials may be delayed because of increased exposures to methylmercury during development. Data from a previously published prospective study in the Faroe Islands have therefore been reexamined. Because of changes in instrumentation, results obtained during the second year of examination were excluded. After this restriction, the results show significant mercury-associated delays of the peak III latency and the I-III interpeak latency of the auditory brainstem evoked potentials. Mercury concentrations in both maternal hair at parturition and in cord blood indicated this association, whereas no such relationship was apparent with the child's current hair-mercury concentration. Thus, in agreement with the findings from Madeira, a delay of the peak III latency of the brainstem auditory evoked potentials appears to serve as a marker of prenatal methylmercury toxicity from contaminated seafood.

Delayed evoked potentials in children exposed to methylmercury from seafood

Methylmercury poisoning may cause constriction of visual fields and deafness, especially if exposure occurs prenatally. However, the risks associated with exposure from contaminated seafood is unclear. We examined 149 children attending first grade in a Madeiran fishing community. As maternal dietary habits were relatively unchanged, current maternal hair concentrations were used as indicator of the child's prenatal exposure to methylmercury (geometric average, 9.64 microg/g [48.2 nmol/g]). After adjustment for age and sex, the mean (+/-SD) latency of peak III of the brainstem auditory evoked potentials at 40 Hz was increased by 0.128+/-0.047 ms when maternal hair-mercury concentrations exceeded 10 microg/g (50 nmol/g) (p for association, 0.002), and the increase of the N145 pattern-reversal visual evoked potential latency at 15 minutes of arc was 3.16+/-1.57 ms (p for association, 0.002). No such relationships were seen with the child's own hair-mercury concentration, and other clinical examinations revealed no mercury-associated deficits. Neurophysiological evidence of adverse effects on brain function are relatively independent of confounders, and should be considered in the risk assessment of this seafood pollutant.

Prenatal methylmercury exposure as a cardiovascular risk factor at seven years of age

Blood pressure in childhood is an important determinant of hypertension risk later in life, and methylmercury exposure is a potential environmental risk factor. A birth cohort of 1,000 children from the Faroe Islands was examined for prenatal exposure to methylmercury, and at age 7 years, blood pressure, heart rate, and heart rate variability were determined. After adjustment for body weight, diastolic and systolic blood pressure increased by 13.9 mmHg [95% confidence limits (CL) = 7.4, 20.4] and 14.6 mmHg (95% CL = 8.3, 20.8), respectively, when cord blood mercury concentrations increased from 1 to 10 microg/liter cord blood. Above this level, which corresponds to a current exposure limit, no further increase was seen. Birth weight acted as a modifier, with the mercury effect being stronger in children with lower birth weights. In boys, heart rate variability decreased with increasing mercury exposures, particularly from 1 to 10 microg/liter cord blood, at which the variability was reduced by 47% (95% CL = 14%, 68%). These findings suggest that prenatal exposure to methylmercury may affect the development of cardiovascular homeostasis.

Isolation of Lyme disease Borrelia from puffins (Fratercula arctica) and seabird ticks (Ixodes uriae) on the Faeroe Islands

This is the first report on the isolation of Lyme disease Borrelia from seabirds on the Faeroe Islands and the characteristics of its enzootic cycle. The major components of the Borrelia cycle include the puffin (Fratercula arctica) as the reservoir and Ixodes uriae as the vector. The importance of this cycle and its impact on the spread of human Lyme borreliosis have not yet been established. Borrelia spirochetes isolated from 2 of 102 sampled puffins were compared to the borreliae previously obtained from seabird ticks, I. uriae. The rrf-rrl intergenic spacer and the rrs and the ospC genes were sequenced and a series of phylogenetic trees were constructed. Sequence data and restriction fragment length polymorphism analysis grouped the strains together with Borrelia garinii. In a seroepidemiological survey performed with residents involved in puffin hunting on the Faeroe Islands, 3 of 81 serum samples were found to be positive by two commonly used clinical tests: a flagellin-based enzyme-linked immunosorbent assay (ELISA) and Western blotting. These three positive serum samples also had high optical density values in a whole-cell ELISA. The finding of seropositive Faeroe Islanders who are regularly exposed to I. uriae indicate that there may be a transfer of B. garinii by this tick species to humans.

Methylmercury dose estimation from umbilical cord concentrations in patients with Minamata disease

The methylmercury exposure of patients with congenital or infantile Minamata disease is known only from a small number of analyses of umbilical cords. Four laboratories in Japan have analyzed a total of 176 samples of umbilical cord tissue obtained from Minamata. The highest concentrations were seen in cord tissue from children born during 1950-1965, i.e., the peak period of acetaldehyde production in Minamata before installation of waste water treatment. Twenty-four samples from patients diagnosed with Minamata disease showed a median mercury concentration of 1.63 microg/g and differed significantly from levels seen in cord tissue from control children. However, children diagnosed with mental retardation had mercury concentrations in cord that were intermediate between the two other groups. Using regression coefficients obtained at a study conducted at the Faroe Islands, the median cord mercury concentration from the children with Minamata disease is estimated to correspond to about 216 microg/L cord blood and 41 microg/g in maternal hair. Based on correlations reported in the literature, the median daily mercury intake of the women whose children developed Minamata disease can then be estimated at about 225 microg. Although these children had fully developed Minamata disease, the estimates of median mercury levels are only four to five times higher than current mercury exposure limits.

Cognitive performance of children prenatally exposed to "safe" levels of methylmercury

Within a cohort of 1022 consecutive singleton births in the Faroe Islands, we assessed prenatal methylmercury exposure from the maternal hair mercury concentration. At approximately 7 years of age, 917 of the children underwent detailed neurobehavioral examination. Little risk is thought to occur as long as the hair mercury concentration in pregnant women is kept below 10-20 microg/g (50-100 nmol/l). A case group of 112 children whose mothers had a hair mercury concentration of 10-20 microg/g was therefore matched to children with exposure below 3 microg/g, using age, sex, time of examination, and the mother's score on Raven's Progressive Matrices as matching criteria. The two groups were almost identical with regard to other factors that might affect neurobehavioral performance in this community. On six neuropsychological test measures, the case group showed mild decrements, relative to controls, especially in the domains of motor function, language, and memory. Subtle effects on brain function therefore seem to be detectable at prenatal methylmercury exposure levels currently considered to be safe.

Cognitive deficit in 7-year-old children with prenatal exposure to methylmercury

A cohort of 1022 consecutive singleton births was generated during 1986-1987 in the Faroe Islands. Increased methylmercury exposure from maternal consumption of pilot whale meat was indicated by mercury concentrations in cord blood and maternal hair. At approximately 7 years of age, 917 of the children underwent detailed neurobehavioral examination. Neuropsychological tests included Finger Tapping; Hand-Eye Coordination; reaction time on a Continuous Performance Test; Wechsler Intelligence Scale for Children-Revised Digit Spans, Similarities, and Block Designs; Bender Visual Motor Gestalt Test; Boston Naming Test; and California Verbal Learning Test (Children). Clinical examination and neurophysiological testing did not reveal any clear-cut mercury-related abnormalities. However, mercury-related neuropsychological dysfunctions were most pronounced in the domains of language, attention, and memory, and to a lesser extent in visuospatial and motor functions. These associations remained after adjustment for covariates and after exclusion of children with maternal hair mercury concentrations above 10 microgram(s) (50 nmol/g). The effects on brain function associated with prenatal methylmercury exposure therefore appear widespread, and early dysfunction is detectable at exposure levels currently considered safe.

Health implications for Faroe islanders of heavy metals and PCBs from pilot whales

In the Faroe Islands marine food constitutes a considerable part of the diet. In addition to fish, both meat and blubber from pilot whales are included in the diet. Muscle tissue of pilot whales caught in the Faroe Islands contains an average mercury concentration of 3.3 micrograms/g (16 nmol/g), about half of which is methylmercury. In some years an evenly distributed annual catch of pilot whales would make the average dietary intake of mercury close to an excess of the Provisional Temporary Weekly Intake of 0.3 mg recommended by WHO. In one out of eight consecutive births, the mercury concentration in maternal hair exceeded a limit of 10 micrograms/g where a risk of neurobehavioral dysfunction in the child may occur; the maximum was 39.1 micrograms/g. Mercury concentrations in umbilical cord blood showed a similar distribution with a maximum of 351 micrograms/l. The large variation in mercury exposure is associated with differences in the frequency of whale dinners. The average PCB concentration in pilot whale blubber is very high, i.e. about 30 micrograms/g. With an estimated daily consumption of 7 g of blubber, the average daily PCB intake could therefore exceed 200 micrograms, i.e. close to the Acceptable Daily Intake. In Scandinavia, the average daily PCB intake is about 15-20 micrograms. To obtain an improved scientific basis for public health action, two major prospective studies have been initiated. A birth cohort of 1000 children has been examined at approximately 7 years of age for neurobehavioral dysfunctions associated with prenatal exposure to mercury and PCB. Preliminary analyses of the data show that several neurobehavioral tests are associated with mercury exposure parameters. With emphasis on prenatal exposures to PCB, another cohort has been generated during 1994-95, and this cohort will be followed closely during the next years.

Feasibility and validity of three computer-assisted neurobehavioral tests in 7-year-old children

Three tests from the computerized Neurobehavioral Examination System (NES) were administered to a group of 917 Faroese children at approximately 7 years of age. The NES Continuous Performance Test (CPT) was modified to use animal silhouettes as stimuli instead of letters. Almost all children completed Finger Tapping (FT), the modified CPT, and Hand-Eye Coordination (HE). However, 18% of the children missed at least 25% of the stimuli on the CPT (full test period), and 37% of the children did not improve their HE performance by at least 10%, as compared to the first trial. Boys obtained better results than girls, and older children performed better than younger ones. However, both factors were confounded by acquaintance with computer games. Children who used glasses, who had strabismus, or who had decreased contrast sensitivity obtained less satisfactory scores, especially on CPT and HE. The NES performance was significantly associated with functional neurological performance, including catching a ball, diadochokinesia, and finger agnosia. Slight, though statistically significant, decrements were seen with increased levels of prenatal exposure to neurotoxicants, as indicated by the mercury concentrations in cord blood obtained at the time of birth. In conclusion, the tests were feasible in this age group after slight modifications, and the test results showed meaningful associations with major predictors, thus supporting the validity of the data.

Neurobehavioral epidemiology: application in risk assessment

Neurobehavioral epidemiology may contribute information to risk assessment in relation to a) characterization of neurotoxicity and its time course; b) the dose-effect relationship; c) the dose-response relationship; and d) predisposing factors. The quality of this information relies on the validity of the exposure data, the validity and sensitivity of neurobehavioral function tests, and the degree to which sources of bias are controlled. With epidemiologic studies of methylmercury-associated neurotoxicity as an example, the field of research involves numerous uncertainties that should be taken into account in the risk assessment process.

Relation of a seafood diet to mercury, selenium, arsenic, and polychlorinated biphenyl and other organochlorine concentrations in human milk

Human transition milk was sampled from 88 mothers at the Faroe Islands, where the seafood diet includes pilot whale meat and blubber. Milk mercury concentrations (median, 2.45 micrograms/liter) were significantly associated with mercury concentrations in cord blood and with the frequency of pilot whale dinners during pregnancy. Milk selenium concentrations (mean, 19.1 micrograms/liter) correlated significantly with concentrations in cord blood but not with seafood consumption. Arsenic concentrations were very low. Twenty-four of the milk samples were separated into four pools based on fish intake and milk mercury concentrations. The polychlorinated biphenyl (PCB) concentrations (1.8-3.5 micrograms/g lipid) were high and mainly due to congener numbers 153, 180, and 138. One pool contained a congener 77 concentration of 1380 ppt, which is the highest ever reported in a human specimen for a coplanar PCB. The highest PCB concentrations were seen in the pools from women who had eaten frequent whale dinners and whose milk contained high mercury concentrations. The concentrations of chlorinated dibenzo-p-dioxins and furans were not similarly elevated. Given the advantages associated with breast-feeding, advice to nursing mothers in this population should take into regard the possible risks associated with long-term exposure to milk contaminants.

Methylmercury: significance of intrauterine and postnatal exposures

Outbreaks of methylmercury poisoning in Japan and Iraq have demonstrated the sensitivity of the fetus to neurotoxic effects. Based on toxicokinetics and considerations of practicability, the optimal biomarker of methylmercury exposure is the hair concentration, but whole-blood measurements of mercury are also useful. Dose-response relations are still incompletely known, especially concentrating developmental neurotoxicity under conditions of chronic exposure. Available evidence indicates that neurobehavioral dysfunction in children may occur if the maternal mercury concentration in hair is > 6 micrograms/g (30 nmol/g). This value corresponds to a blood mercury concentration of approximately 24 micrograms/L (120 nmol/L). The period of maximum sensitivity of the nervous system to methylmercury toxicity is unknown, but the transfer of mercury to the newborn through human milk may represent an additional risk. In view of the wide occurrence of mercury contamination in developing countries, increased use of the exposure biomarkers is encouraged.

Methylmercury: significance of intrauterine and postnatal exposures

Outbreaks of methylmercury poisoning in Japan and Iraq have demonstrated the sensitivity of the fetus to neurotoxic effects. Based on toxicokinetics and considerations of practicability, the optimal biomarker of methylmercury exposure is the hair concentration, but whole-blood measurements of mercury are also useful. Dose-response relations are still incompletely known, especially concentrating developmental neurotoxicity under conditions of chronic exposure. Available evidence indicates that neurobehavioral dysfunction in children may occur if the maternal mercury concentration in hair is &gt; 6 micrograms/g (30 nmol/g). This value corresponds to a blood mercury concentration of approximately 24 micrograms/L (120 nmol/L). The period of maximum sensitivity of the nervous system to methylmercury toxicity is unknown, but the transfer of mercury to the newborn through human milk may represent an additional risk. In view of the wide occurrence of mercury contamination in developing countries, increased use of the exposure biomarkers is encouraged.

Mercury in the Umbilical Cord: Implications for Risk Assessment for Minamata Disease

Umbilical cord tissue was obtained from 50 births in the Faroe Islands, where high mercury intake is due to ingestion of pilot whale meat. The mercury concentration correlated significantly with the frequency of maternal whale meat dinners during pregnancy and with mercury concentrations in umbilical cord blood and in maternal hair. The results were compared with published values for mercury in umbilical cord tissue from 12 infants diagnosed with congenital methylmercury poisoning in Minamata, Japan. From the regression coefficients obtained in the Faroese samples, the median umbilical cord mercury concentration of 4.95 nmol/g dry weight in Minamata would correspond to 668 nmol/l cord blood and 114 nmol/g maternal hair. These levels agree well with other evidence of susceptibility of the fetus to increased exposure to methylmercury.

Human milk as a source of methylmercury exposure in infants

As methylmercury is excreted in human milk and infants are particularly susceptible to toxicity due to this compound, the purpose of this study was to evaluate the possible transfer of methylmercury to infants via breast-feeding. In a community with a high intake of seafood, 583 children from a birth cohort were followed. The duration of nursing was recorded, and hair samples were obtained for mercury analysis at approximately 12 months of age. The hair mercury concentrations increased with the length of the nursing period, and those nursed throughout the first year showed the highest geometric mean (9.0 nmol/g or 1.8 microg/g). Human milk therefore seems to be an important source of methylmercury exposure in infants. An increasing time interval from weaning to hair sample collection was not associated with any detectable decrease in mercury concentrations. A slow or absent elimination of methylmercury during the first year after birth could explain this finding. In certain fishing communities, infants nursed for long periods may be at increased risk of developing methylmercury toxicity.

Frequency of seafood intake in pregnancy as a determinant of birth weight: evidence for a dose dependent relationship

STUDY OBJECTIVE

The aim was to explore whether maternal consumption of seafood is a determinant of birth weight in a dose dependent manner.

DESIGN

A population based survey of lifestyle factors in pregnancy was linked with information from antenatal and obstetric records.

SETTING AND PARTICIPANTS

Seventy five per cent of all 1362 women who delivered in the Faroe Islands during the study period 1986-87 who gave a structured post partum interview on lifestyle factors.

MAIN RESULTS

Altogether, 2, 6, 16, 33, 26, 14, and 3% of women had consumed approximately 0, 1, 2, 3, 4, 5, and 6+ respectively seafood (fish or whale) dinner meals per week during pregnancy. The average birth weight (p = 0.02) and birth length (p = 0.002) varied significantly between the seven groups, and increased by about 0.2 kg and 1 cm, respectively between women who ate 0 and those who consumed 3 seafood meals per week. Mean birth weight and length tended to level off with further fish consumption: when fitting a second degree polynomial, the quadratic terms were negative and significant for both birth weight (p = 0.005) and length (p = 0.001). Analogous analyses for pregnancy duration were not significant, but exhibited similar trends. All analyses were adjusted for maternal height, weight, parity, age, marital status, and smoking.

CONCLUSIONS

The weight and length of the newborn increased with the frequency of seafood dinner meals consumed in pregnancy but only up to a consumption level of about 3 meals per week.

Neurobehavioral effects of intrauterine mercury exposure: potential sources of bias

Sources of bias were examined in a study of neurobehavioral effects of intrauterine exposure to methyl mercury in the Faroe Islands. The cohort of 1000 children was born during a 21-month period and did not differ from Faroese births in general as regards major obstetrical parameters. However, high mercury concentrations in the cord blood was associated with increased birth weight, presumably because other constituents of marine fish may cause a prolongation of the gestation period. Thus, children with high mercury exposures were somewhat protected against low birth weight and its associated neurobehavioral risks. Less than 25% of the women indicated occasional alcohol drinking during pregnancy, thus suggesting a limited fetal exposure to this neurobehavioral risk factor. However, maternal alcohol drinking caused a decrease in mercury concentrations in cord blood, probably because of a toxicokinetic interaction between ethanol and mercury. Any alcohol-related effect on neurobehavioral development would then be associated with lower levels of mercury exposures. The effects of these confounders would tend to bias the results of the study toward the null hypothesis.

Screening for complement deficiencies in patients surviving from epidemic meningococcal disease

Sera from 132 patients surviving from meningococcal disease during the high-endemic period 1 January 1980 to 31 December 1984 on the Faroe Islands were screened for deficiencies of the complement (C) system by measuring hemolytic complement function in serum. Samples from 12 patients with reduced C function were further investigated by immunochemical quantification of individual C proteins. One patients was identified with C3-deficiency (C3-concentration 6% of normal) due to the presence of C3 nephritic factor (C3NeF) in serum. In addition, eight patients had minor aberrations in one or several complement proteins. It is concluded, that C deficiency is not an important risk factor during epidemics of meningococcal disease. The C3NeF activity could not be absorbed with Neisseria meningitidis group B, type 15, indicating absence of crossreactivity between neisserial antigens and C3NeF.

An epidemic outbreak of group B meningococcal disease on the Faroe Islands

An epidemic of group B meningococcal disease on the Faroe Islands is described. A peak annual incidence of 95 cases/100,000 was reached in 1981. The time at which the epidemic commenced cannot be determined due to inadequate diagnostic facilities, but was presumably around the end of the 1970s. The incidence fell to 29 cases/100,000 in 1985, which indicates that the Faroe Islands are still a high incidence area. A total of 203 cases of meningococcal disease were recorded during the period 1978-1985 with 11 deaths (lethality rate 5.4%). After rifampicin was introduced in 1981 as prophylactic treatment against secondary cases, 1,892 persons were treated with this agent and none of these appeared in the study population. Before rifampicin prophylaxis was introduced, the number of cases were distributed with an evenly increasing incidence in the capital and in the provinces. Following the introduction of rifampicin as prophylactic agent, a fall in the incidence in both areas was observed. This fall was more pronounced in the capital, where the number of prescribed prophylactic doses per case of meningococcal disease was higher than in the province.

Hepatic microsomal enzyme function in technicians and anesthesiologists exposed to halothane and nitrous oxide

It is controversial whether daily occupational exposure to halothane stimulates (induces) the hepatic microsomal enzyme function in man. We investigated two groups of persons with different degrees of exposure to halothane: Six technicians who for years had been employed with repair and control of anesthesiologic equipment resulting in exposure to about 7 ppm of halothane and 50 ppm of nitrous oxide, and seven anesthesiologists exposed during months to about 2 ppm of halothane and 75 ppm of nitrous oxide. The clearance of antipyrine was determined from saliva concentrations before and 4 wk after discontinuation of exposure. Matched control persons were investigated simultaneously. No significant differences were found between the half-life, apparent volume of distribution, or clearance of antipyrine either within the groups or between the groups. If the antipyrine data from both exposure groups are compared to those of the control groups, the data exclude (95% confidence limit) that antipyrine metabolism increased by more than 3% during exposure to waste anesthetics. This indicates that occupational exposure to halothane in concentrations above the proposed maximal time weighted average concentration of 2 ppm does not change the microsomal activity.