Can Flanders resist the measles outbreak? Assessing vaccination coverage in different age groups among Flemish residents.

The Belgian strategic plan to eliminate measles contains several vaccination strategies including routine immunisation programmes and catch-up campaigns. A new expanded programme on immunisation-based survey (2016) assessed the uptake of the recommended measles-mumps-rubella (MMR) vaccine in three different cohorts: toddlers, adolescents and parents of toddlers. A two-stage cluster sampling technique was used to select 875 toddlers (age 18-24 months) and 1250 adolescents (born in 2000) from 107 municipalities in Flanders. After consent of the parent(s), 746 (85.2%) families of toddlers and 1012 (81.0%) families of adolescents were interviewed at home. Measles vaccination coverage was high at 18-24 months (96.2%) and 81.5% were vaccinated at recommended age. Toddlers who had two siblings or a non-working mother or changed vaccinator were more at risk for not being vaccinated. Coverage of the teenager dose reached 93.5% and was lower in adolescents with educational underachievement or whose mother was part-time working or with a non-Belgian background. Only 56.0% of mothers and 48.3% of fathers remembered having received at least one measles-containing vaccine. Although measles vaccination coverage in toddlers meets the required standards for elimination, administration of the teenager dose of MMR vaccine and parent compliance to the recent measles catch-up campaign in Flanders leave room for improvement.

Evaluating the implementation fidelity of a multicomponent intervention for oral health promotion in preschool children.

This study evaluates the process of implementation of a longitudinal intervention program to promote oral health in preschool children in Flanders, Belgium. As the program was implemented in an existing preventive health care organization, the study also evaluates this setting as the context for implementation. Qualitative and quantitative methods were used to evaluate implementation fidelity, based on Carroll's theoretical framework of implementation fidelity (Carroll et al., Implementation Science 2:40, 2007). Questionnaire data from participants and health workers were analyzed, and document analyses were performed to compare registrations of the actions with the planning manual. Results were mixed. Whereas more than 88 % of all parents attended all home visits, only 57 % received at least 9 of the 11 planned consultations. Fifty-two percent of the families received all supporting materials, and on average, 73 % of all attending families received all information at a contact as described in the manual. Moderating factors such as the adequate use of facilitators and high participant responsiveness had a positive impact on implementation fidelity, whereas the quality of delivery differed to a great extent between the nurses who were involved during the entire intervention period and those who gave only a few sessions. Implementing an intervention in an existing well-baby program has many advantages, although lack of time presents a challenge to implementation fidelity. The results of this process evaluation allow a better understanding of the contribution of implementation fidelity to the effectiveness of health promotion programs.

Rotavirus vaccination coverage and adherence to recommended age among infants in Flanders (Belgium) in 2012.

In Belgium, rotavirus vaccination has been recommended and partially reimbursed since October 2006. Through a retrospective survey in 2012, we estimated the coverage rate of the rotavirus vaccination in Flanders among infants born in 2010. Using a standardised questionnaire, 874 families were interviewed at home, collecting information on demographic characteristics, socio-economic background and documented vaccination history (updated from medical files and vaccination database, if needed). Adherence to the recommended age for vaccination (8, 12 and 16 weeks) was also assessed. The coverage rate for two doses of rotavirus vaccination was 92.2% (95% confidence interval: 90.2-93.8). Respectively 31.7% and 10.1% of the children received their first and second dose at the recommended age. Incomplete vaccination was often a deliberate choice of the parents. Only eight children (1%) were vaccinated after the maximum age of 26 weeks. Factors identified by multiple logistic regression as related to incomplete vaccination were: living in the province of Antwerp, unemployed mother, and three or more older siblings in the household. Four years after introduction, the coverage rates were surprisingly high for a vaccine that is not fully reimbursed and not readily available in the vaccinator's fridge, which is the case for the other recommended infant vaccines.

Universal hepatitis B vaccination in Belgium: impact on serological markers 3 and 7 years after implementation.

Hepatitis B virus (HBV) can be eliminated by effective universal vaccination. In Belgium, a free-of-charge HBV vaccination programme in infants with catch-up in adolescents was introduced in 1999. To evaluate the effects in <20-year-olds, seroprotection (anti-HBs >11 mIU/ml, according to the assay) and markers of infection (anti-HBc, HBsAg) were assessed in 2443 residual sera collected 7-8 years after implementation of the programme. The maximal prevalence of a solely anti-HBs seroprotective ('vaccinated') serostatus was 82·9% at age 1 year and 60·5% at age 13 years. A clear increase was found in age cohorts targeted by the campaign after a similar serosurvey conducted 4 years earlier. The prevalence of HBV infection remained unchanged at a low level (1·8% in 2006) similar to pre-vaccination data (1993-1994). We conclude that universal HBV vaccination has achieved overall high levels of vaccine-induced immunity, despite regional variations, which may give rise to pockets of susceptible young adults in the future.

Prevalence of endometriosis diagnosed by laparoscopy in adolescents with dysmenorrhea or chronic pelvic pain: a systematic review.

BACKGROUND Endometriosis associated with pain symptoms in adolescents has been extensively reported, but the exact prevalence is unclear because pain symptoms may be atypical and endometriosis can only be diagnosed by laparoscopy. The aim of this paper is to provide a systematic review of the prevalence of endometriosis diagnosed by laparoscopy in adolescents. METHODS A systematic literature search was carried out for relevant articles published between 1980 and 2011 in the databases PUBMED and EMBASE, based on the keywords 'endometriosis', 'laparoscopy', 'adolescents' and 'chronic pelvic pain (CPP)'. In addition, the reference lists of the selected articles were examined. RESULTS Based on 15 selected studies, the overall prevalence of visually confirmed endometriosis was 62% (543/880; range 25-100%) in all adolescent girls undergoing laparoscopic investigation, 75% (237/314) in girls with CPP resistant to treatment, 70% (102/146) in girls with dysmenorrhea and 49% (204/420) in girls with CPP that is not necessarily resistant to treatment. Among the adolescent girls with endometriosis, the overall prevalence of American Society of Reproductive Medicine classified moderate-severe endometriosis was 32% (82/259) in all girls, 16% (17/108) in girls with CPP resistant to treatment, 29% (21/74) in girls with dysmenorrhea and 57% (44/77) in girls with CPP that is not necessarily resistant to treatment. Due to the quality of the included papers an overestimation of the prevalence and/or severity of endometriosis is possible. CONCLUSIONS About two-thirds of adolescent girls with CPP or dysmenorrhea have laparoscopic evidence of endometriosis. About one-third of these adolescents with endometriosis have moderate-severe disease. The value of early detection of endometriosis in symptomatic adolescents and the indications for laparoscopic investigation in adolescents require more research.

Measuring determinants of oral health behaviour in parents of preschool children.

OBJECTIVE: The aim of this study was to develop a valid and reliable measure for oral health behaviour and its determinants in five-year-old Flemish children, based on the Theory of Planned Behaviour (TPB) and to test its predictive validity. METHODS: 1157 parents of five-year-olds completed a questionnaire measuring three behaviours related to oral health among children (dietary habits, oral hygiene, dental attendance) and their determinants (attitude, subjective norms, perceived behavioural control, intention). The sample was randomly split in two halves and principal component analyses were performed on one half sample to identify the factor structure. Confirmatory factor analyses were performed on the remaining half sample to obtain a cross-validation. Predictive validity was tested using multiple regression analyses. RESULTS: For each behaviour four component structures reflecting the TPB-dimensions, accounting for 44% to 55% of the variance were retrieved and confirmed in the cross-validation. Internal consistency (Cronbach's alpha) of the scales ranged from 0.52 to 0.80. A sizeable percentage of variance of intentions and behaviours was explained by the model. CONCLUSIONS: The TPB components were significant predictors of intentions and behaviours. These findings argue for the reliability and validity of the questionnaire for exploring determinants underlying parental oral health behaviour.

Oral health and oral health-related behaviour in preschool children: evidence for a social gradient.

This study aims to investigate the social gradient in the reported oral health-related behaviour and oral health status of preschool children. Participants were 1,057 children born between October 2003 and July 2004 in Flanders, Belgium. Oral health examinations were performed by trained dentists when the children were 3 and 5 years old (respectively, in 2007 and 2009); data on dietary habits, oral hygiene habits and dental attendance of the children were obtained through structured questionnaires completed by the parents. Maternal educational level, measured in four categories, was used as a proxy of socio-economic status. Logistic and ordinal regressions showed a social gradient for the oral health-related behaviours: a lower educational level of the mother was related to a higher consumption of sugared drinks between meals and to a lower brushing frequency and dental attendance of the child. Children from low-educated mothers also had seven times more chance to present with caries experience than children from mothers with a bachelor degree. Contrary to the expectations, there was a deviation from the gradient in 3-year-olds from the highest educational group showing an increased risk for caries experience (OR = 3.84, 95 % CI = 1.08-13.65). Conclusion. Already in very young children, a graded relationship is observed between socio-economic position, oral health and related behaviours. The results suggest that different approaches are required to promote oral health during early childhood depending on the mother's educational background. As children from the highest social group also have an increased caries risk, specific techniques may be needed.

Effects of time and socio-economic status on the determinants of oral health-related behaviours of parents of preschool children.

The oral health-related beliefs of parents have an important impact on the oral health status of their children; however, they are not stable over time. This study aimed to assess the changes, over time, in the determinants of parental oral health-related behaviour based on the Theory of Planned Behaviour and to investigate socio-economic inequalities. The cohort consisted of the parents - mainly the mothers - of 1,057 children born in 2003 and 2004 in Flanders (Belgium). According to the Theory of Planned Behaviour, validated questionnaires, completed at children's birth and at age 3 and 5 yr, assessed parental attitudes, social norms, perceived behavioural control, and intention towards three behaviours: dietary habits, oral hygiene habits, and dental attendance. Linear mixed-model analyses were applied. Positive parental attitudes towards oral health-related behaviours increased between birth and 3 yr of age, whereas the scores for subjective norms and intentions decreased. Scores remained stable for children between three and 5 yr of age. Highly educated mothers had significantly higher scores for attitudes, perceived behavioural control, and intentions than less-educated mothers. Health promotion campaigns should take these natural changes and inequalities of dental beliefs into account when developing and evaluating interventions.

Immunogenicity and safety of a measles-mumps-rubella-varicella vaccine following a 4-week or a 12-month interval between two doses.

BACKGROUND: The MMRV combination vaccine, Priorix-Tetra™, is currently licensed in several European countries using a two-dose schedule in infants aged ≥9 months, with a preferred 6-week to 3-month interval between doses. This study was undertaken to generate safety and immunogenicity data for two doses of MMRV vaccine administered according to dose schedules using the shortest permitted interval of 4 weeks versus a longer interval of 12 months, which would allow flexible adaptation to local immunization calendars. METHODS: Healthy children aged 11-13 months were randomized (1:1:1) to receive 2 doses of either: MMRV vaccine with a 4-week interval between doses (MMRV-4W group, N=188), MMRV vaccine with a 12-month interval between doses (MMRV-12M group, N=184), or MMR vaccine with a 4-week interval between doses (MMR group, N=187). Blood samples were taken prior to, and 4-6 weeks after each vaccination. RESULTS: Post-Dose 2, both MMRV groups exhibited an adequate immunogenic response for all components; however the MMRV-12M group showed significantly greater geometric mean titers for mumps, rubella and varicella. Two varicella breakthrough cases occurred within the 12-month interval between doses in the MMRV-12M group. Local and general reactogenicity results were similar for all groups except for the MMRV-4W group, which had a greater incidence of fever during Days 0-14 post-Dose 1. CONCLUSIONS: Two doses of MMRV vaccine administered in the second year of life elicited adequate immunogenicity and were well-tolerated whether administered with a dose interval of 4 weeks or 12 months.

Are we hitting immunity targets? The 2006 age-specific seroprevalence of measles, mumps, rubella, diphtheria and tetanus in Belgium.

Susceptibility to vaccine-preventable diseases in Belgium in 2006 was estimated from a serum survey. Immunoglobulins against measles, mumps, rubella (MMR) and diphtheria at all available ages (1-65 years), and against tetanus in >40-year-olds, were measured by ELISA. Age-standardized overall seronegativity for MMR was low (3·9%, 8·0%, 10·4%, respectively). However, the World Health Organization's targets for measles elimination were not met in 5- to 24-year-olds and about 1 in 7 women at childbearing age (15-39 years) were seronegative for rubella. In adults >40 years, tetanus immunity (87·2%, >0·16 IU/ml) largely exceeded diphtheria immunity (20-45%, >0·1 IU/ml). Despite free universal vaccination against MMR for more than 20 years and against diphtheria and tetanus for almost 60 years, our study revealed specific age groups remaining at risk for infection with these pathogens.

Growth of Belgian and Norwegian children compared to the WHO growth standards: prevalence below -2 and above +2 SD and the effect of breastfeeding.

BACKGROUND: New national growth references have been published in Belgium and Norway. The WHO recommends universal use of their 2006 Child Growth Standards based on data from breastfed children. OBJECTIVE: To compare the growth of Belgian and Norwegian children with the WHO standards. PARTICIPANTS: 6985 children 0-5 years of age from Belgium and Norway. DESIGN: Proportion of children below -2 SD and above +2 SD of the WHO standards was calculated for length/height, weight, body mass index and head circumference. Average SD scores of exclusively breastfed children of non-smoking mothers were compared with national reference data and with the WHO standards. RESULTS: Generally, the number of Belgian and Norwegian children below -2 SD lines of the WHO standards was lower and above +2 SD higher than expected. The largest differences were for head circumference (0.97% Belgian and 0.18% Norwegian children below -2 SD, 6.55% Belgian and 6.40% Norwegian children above +2 SD) and the smallest for length/height (1.25% Belgian and 1.43% Norwegian children below -2 SD, 3.47% Belgian and 2.81% Norwegian children above +2 SD). The growth pattern of breastfed children of non-smoking mothers was in both countries more alike the local national growth references than the WHO standards. CONCLUSIONS: There are significant deviations in the proportion of children outside normal limits (±2 SD) of the WHO standards. This was true for all children, including those who were exclusively breastfed. Hence, adoption of the WHO growth charts could have consequences for clinical decision-making. These findings advocate the use of national references in Belgium and Norway, also for breastfed children.

References for growth and pubertal development from birth to 21 years in Flanders, Belgium.

BACKGROUND: Due to the secular trend in length and height, growth references need to be updated regularly. Reference charts that were until recently used in Belgium are based on samples collected more than 30 years ago, and references for body mass index (BMI) and pubertal development have not been established before. AIMS: To establish contemporary cross-sectional reference charts for height, weight, BMI, head circumference, and pubertal development from birth to 21 years of age, based on a representative sample of children from Flanders, Belgium. SUBJECTS AND METHODS: 15 989 healthy subjects of Belgian origin, 0-25 years of age, were measured in 2002-2004. Growth curves were fitted with the LMS method, and percentiles for the pubertal development were estimated with generalized additive models on status quo data from 8690 subjects aged 6-22 years of age. RESULTS: A positive secular trend in height and weight is observed in children above 5 years of age. Adult median height has increased by 1.2 cm/decade in boys and 0.8 cm/decade in girls; median weight by 0.9 kg/decade in boys, and 1.0 kg/decade in girls, and the weight distribution became more skewed. The BMI curve is comparable to that of other populations, except for higher percentiles. This reflects the increasing prevalence of overweight and obesity. Median age at menarche (13.0 years) has not advanced any more over the past 50 years. Median ages at menarche and B2 in girls and G2 or T4 in boys are comparable to other West European estimates, but approximately 10% enter G2/T4 before 9 years of age. CONCLUSIONS: The ongoing secular trend in height and weight makes growth charts previously used in Belgium obsolete. New representative charts for growth and pubertal development are introduced. For weight monitoring, it is advised that the now-available BMI growth charts are used.

Measuring oral health behaviour in Flemish health care workers: an application of the theory of planned behaviour.

OBJECTIVE: This study describes the development and validation of a questionnaire to measure the determinants of oral health related behaviour in health care workers, based on the Theory of Planned Behaviour (TPB). RESEARCH DESIGN: A preliminary questionnaire was drafted containing 78 self report items measuring three behaviours related to oral health (i.e. dietary habits, oral hygiene habits and dental attendance), as well as the attitudes, perceived social norms and self-efficacy for each behaviour. The questionnaire was completed by 201 health care workers for the initial validation and 966 other health care workers for a replication. OUTCOMES: A principal component analysis with Procrustes rotation toward an a priori three component structure on the original sample yielded high congruence measures for reported dental attendance, but not for dietary habits and oral hygiene habits. Subsequent exploratory Varimax rotations and discarding of redundant items resulted in three component solutions explaining 43% of the variance in dietary habits, 57% in oral hygiene habits and 66% in dental attendance, respectively. For all three behaviours, these components corresponded to the dimensions of the TPB. Internal consistency of the scales was satisfactory, with Chronbach's alpha's ranging from 0.51 to 0.87. Scale scores accounted for a significant proportion of the variance in the intention to avoid sweet snacks, to brush teeth, and to attend dental check-ups, and of the frequency of consumption of sweet drinks and frequency of brushing. A confirmatory factor analysis on the larger sample of 966 health care workers provided excellent goodness of fit indices, confirming the construct validity of the scales.

Parental smoking behavior and caries experience in preschool children.

OBJECTIVES: The study aimed to explore the association between parental smoking behavior and caries experience in young children, taking into account the socioeconomic status and oral health-related behavior. METHODS: Cross-sectional data from 1250 3-year-old and 1283 5-year-old children from four geographical areas in Flanders (Belgium) were analyzed. Children were examined at school by trained dentist-examiners, using standard criteria and calibrated examination methodology. Data on oral hygiene and dietary habits, oral health behavior, sociodemographic variables, and parental smoking behavior were obtained through structured questionnaires, completed by the parents. RESULTS: Visible caries experience (i.e. d(3)mft > 0) was seen in 7% of 3-year olds and 31% of 5-year olds. In both age groups, 30% of the parents reported smoking behavior. Univariable logistic regression analysis with caries prevalence as the dependent variable, revealed that parental smoking was a significant independent variable. After controlling for age, gender, sociodemographic characteristics, oral hygiene, and dietary habits, the effect of family smoking status was no longer significant in 3-year-old children (OR = 1.98; 95% CI: 0.68-5.76). In 5-year olds the significant relationship between parental smoking behavior and caries experience persisted after adjusting for the other evaluated variables (OR = 3.36; 95% CI: 1.49-7.58). CONCLUSION: The results of this study illustrate the existence of a significant association between parental smoking behavior and caries experience in 5-year-old children.

Administration of hepatitis A vaccine at 6 and 12 months of age concomitantly with hexavalent (DTaP-IPV-PRP approximately T-HBs) combination vaccine.

BACKGROUND: Administration of two doses of hepatitis A (HA) vaccine to children > or = 2 years of age has been shown to be protective. The present study assessed whether HA vaccine can be administered as early as 6 months of age and whether it can be administered concomitantly with a hexavalent (HV) vaccine at this age. METHODS: In an open label, randomized, parallel group study, the liquid HV vaccine (HEXAVAC) (diphtheria, tetanus, 2-component acellular pertussis, inactivated poliomyelitis vaccine, Haemophilus influenzae type b conjugated to tetanus protein and hepatitis B) was administered at 2, 4, 6, and 12 months of age to all children. HA vaccine (VAQTA) was given at 7 and 13 months in the separate administration group (Group 1) and at 6 and 12 months in the concomitant administration group (Group 2). Serum samples were obtained at 2, 7, 12, and 14 months in Group 1 and at 2, 7, 12, and 13 months in Group 2. The primary immunogenicity outcomes were the seroconversion rates for HA 1 month after the second dose of HA vaccine in initially seronegative subjects, and the seroconversion rates for each HV antigen 1 month after the third dose of the HV vaccine (both at 7 months of age). RESULTS: HA seropositivity rates 1 month after the second dose were 100% in both groups, regardless of initial serostatus. The responses to each HV antigen 1 month after the third dose were similar in both groups. The vaccines were generally well tolerated in both groups regardless of vaccine(s) administered. CONCLUSIONS: A schedule of two doses of HA vaccine, 6 months apart beginning at 6 months of age is highly immunogenic and well tolerated when administered alone or concomitantly with HV vaccine at 6 and 12 months of age.

Effects of lowering the aluminium content of a dTpa vaccine on its immunogenicity and reactogenicity when given as a booster to adolescents.

As aluminium in vaccines has been associated with the incidence of local side effects occurring after vaccination, this observer-blind randomised clinical trial was designed to evaluate the effect of lowering the aluminium content of a combined reduced-antigen-content dTpa vaccine on immunogenicity and safety when administered to healthy adolescents aged 10-18 years. A total of 647 subjects were enrolled, 224 (35%) received a dTpa formulation with 0.5 mg aluminium, 209 (32%) a formulation with 0.3 mg aluminium and 214 (33%) a formulation with 0.133 mg aluminium. One month after boostering, all subjects were seroprotected against diphtheria and tetanus toxoids. All subjects were seropositive for anti-FHA and anti-PRN but 4% of the initially seronegatives in both reduced aluminium groups did not seroconvert for anti-PT. Booster responses did not differ significantly between groups for any antibody, but post booster vaccination anti-PT GMC's differed significantly between groups and decreased when vaccine aluminium content decreased. No clear difference between study groups in local or general side effects was demonstrated. The most frequently reported symptoms after vaccination were injection site pain (89.5-90.7%), fatigue (42.1-47.4%) and headache (41.1-45.1%). This study showed that the aluminium content has a specific influence on the immunogenicity of this dTpa vaccine.

CUGE: a screening instrument for alcohol abuse and dependence in students.

OBJECTIVES: The prevalence of alcohol abuse on college campuses ranges from 7 to 17%. Frequent heavy drinkers place themselves and others at risk for a variety of adverse consequences and frequently remain undetected. Brief individual interventions result in a significant reduction on the number of drinks. Therefore, detection of students at risk is useful and desirable. The CUGE has been elsewhere described as a promising screening device for problem drinking in students. In order to determine the diagnostic value of this new questionnaire, we set up a validation study in a new and independent population of freshmen. METHODS: A cross-sectional diagnostic study. Participants were college freshmen of the Katholieke Universiteit Leuven. All students received a questionnaire, containing the CUGE, being the test of interest, and the CIDI as the reference test. RESULTS: The CUGE combines a very high sensitivity of 91% with a reasonable specificity of 76.3% in this validation group. CONCLUSIONS: The CUGE is an excellent screening device in this population of students. In addition, it is a short questionnaire with only yes or no questions. This makes the CUGE easily applicable as a part of broad routine questionnaires.

Does vitamin C supplementation influence the levels of circulating oxidized LDL, sICAM-1, sVCAM-1 and vWF-antigen in healthy male smokers?

OBJECTIVE: To examine the effects of vitamin C supplementation on the concentration of oxidation markers, in particular, circulating oxidized LDL (OxLDL) and on endothelial activation markers. DESIGN: Randomized double-blind, placebo-controlled crossover trial. SETTING: Belgian population of the city of Leuven. SUBJECTS: A total of 34 healthy male smokers aged 26-73 y. INTERVENTION: Smokers were randomly assigned to receive either vitamin C (250 mg twice daily) or placebo capsules, each to be taken for 4 weeks. After a 1-week washout period, participants then crossed over to the alternative capsules for further 4 weeks. MEAN OUTCOME MEASURES: Markers of oxidation (bilirubin, uric acid, alpha-tocopherol, retinol, malondialdehyde, circulating Oxidized LDL (OxLDL)) and markers of endothelial activation (sICAM-1, sVCAM-1, vWF-antigen) were analysed. RESULTS: Plasma ascorbate concentrations significantly increased from 46.6+/-17.6 to 70.1+/-21.2 mumol/l after a 4-week treatment with 500 mg vitamin C per day. The other plasma antioxidants concentrations, including bilirubin, uric acid, alpha-tocopherol and retinol, were similar in both treatment periods. Vitamin C did not change plasma malondialdehyde and circulating OxLDL compared with placebo (vitamin C 0.73+/-0.25 mg/dl OxLDL; placebo 0.72+/-0.21 mg/dl OxLDL). After vitamin C supplementation, neither sICAM-1 and sVCAM-1 levels nor the concentration of vWF-antigen significantly differed from placebo condition. CONCLUSIONS: Oral supplementation of vitamin C is not associated with changes in markers of oxidation or endothelial activation in healthy male smokers.

Renal function, cytogenetic measurements, and sexual development in adolescents in relation to environmental pollutants: a feasibility study of biomarkers.

BACKGROUND: Human exposure to chemicals is normally monitored by measurement of environmental pollutants in external media. We investigated whether biomarkers in adolescents can show exposure to, and health effects of, common environmental pollutants. METHODS: We recruited 200 17-year-old adolescents (120 girls) from a rural control area and from two suburbs polluted by a lead smelter and two waste incinerators. We measured biomarkers of exposure and of effect in blood and urine samples, and obtained questionnaire data. School doctors measured testicular volume and staged sexual maturation. FINDINGS: Internal exposure was mostly within current standards. Concentrations of lead and cadmium in blood, PCBs (polychlorinated biphenyls) and dioxin-like compounds in serum samples, and metabolites of VOCs (volatile organic compounds) in urine were higher in one or both suburbs than in the control area. Children who lived near the waste incinerators matured sexually at an older age than others, and testicular volume was smaller in boys from the suburbs than in controls. Biomarkers of glomerular or tubular renal dysfunction in individuals were positively correlated with blood lead. Biomarkers of DNA damage were positively correlated with urinary metabolites of PAHs (polycyclic aromatic hydrocarbons) and VOCs. Interpretation Biomarkers can be used to detect environmental exposure to pollutants and measure their biological effects before overt disease develops. Our findings suggest that current environmental standards are insufficient to avoid measurable biological effects.