Short summary of the VIII International Symposium on Hypoxia (Lake Lewis, Canada, February 9-13, 1993)

Paresthesias are a frequently reported symptom of methylmercury exposure in adults, while peripheral neuropathy has long been known to result from high-level lead exposure. Despite this, no objective determination of somatosensory function has been performed in either humans or animals for either toxicant. Somatosensory function was assessed following developmental methylmercury exposure or lifetime lead exposure in monkeys (Macaca fascicularis) by determination of sensitivity to vibration applied to the fingertip. Vibration thresholds were determined over a number of frequencies, from 25 to 250 Hz, by means of a behavioral procedure. The underside of the tip of the monkey's middle finger was precisely positioned over a blunt probe attached to a vibrator. The monkey signaled detection of the vibration by breaking contact with a stainless steel bar with the free hand. At each of the five frequencies tested, the amplitude of the vibration was manipulated systematically to determine the monkey's threshold of detection. Four of five monkeys dosed with methylmercury from birth to 7 years of age, with blood mercury levels during dosing of 0.8-1.1 micrograms/g, exhibited elevated thresholds when tested at 18 years of age. Two monkeys dosed in utero through 4 years of age, with blood mercury levels of 0.35 micrograms/g during dosing, were impaired when tested at 15 years of age, while two monkeys with histories of blood mercury levels of 0.70 were relatively unimpaired. Lifetime exposure to lead resulting in stable blood lead levels of 20-25 micrograms/dl resulted in elevated vibration sensitivity only at the highest frequency in all four individuals tested. However, only two of six individuals with high lead levels (60-130 micrograms/dl) exhibited impairment. These results represent severe impairment in methylmercury-exposed monkeys 11 years after cessation of dosing and extend previous research documenting visual and auditory impairment in these monkeys. While effects of lifetime lead exposure on vibration sensitivity observed in the present study are suggestive, there is clearly a need for further research.     

Effects of lifetime lead exposure on spatial and temporal visual function in monkeys

Detailed characterization of several aspects of visual function was performed in two groups of monkeys (Macaca fascicularis) exposed to lead continuously from birth. One group of four monkeys was dosed from birth onward with 500 microg/kg/day of lead as lead acetate, while another group of six monkeys was dosed with 2000 microg/kg/day. Blood lead levels peaked in the former group at 50 microg/dl early in life; the latter group had peak blood lead concentrations averaging 115 microg/dl during infancy. Blood lead concentrations decreased before one year of age to stable levels of 25 or 35 microg/dl in the low and high dose groups respectively. Spatial and temporal visual function was assessed using a psychophysical procedure at 7-9 years of age. Six age-matched controls were tested concurrently. Two treated monkeys had severe hyperopia: one was assessed on temporal vision only and the other was not assessed. Spatial data from a third monkey were considered suspect and excluded. Six of the nine treated monkeys in which temporal vision was assessed had thresholds below control values at low and/or middle frequencies under high luminance conditions. Low-luminance temporal vision was not affected. There was no evidence of impairment of spatial visual function in lead-exposed monkeys with normal refractive status at either high or low luminance. This study suggests that temporal visual function may be preferentially impaired as a result of lifetime exposure to a moderate body burden of lead, although these results require replication before definitive conclusions may be drawn.     

Effect of long-term lead exposure on hematology, blood biochemistry, and growth curves in monkeys

A total of 90 monkeys (Macaca fascicularis), comprising four study cohorts born over a seven-year period, were hand reared and dosed orally with lead or vehicle according to one of several protocols, in most cases from birth to 9-14 years. Blood lead concentrations of lead-exposed groups ranged from 10 to 90 micrograms/dl depending on dose and age. Routine hematology and blood biochemistry analyses were performed regularly. Comparison of treated groups at various ages to the appropriate control group revealed no strong indication of lead-related effects. In addition, body weight increase was modeled from days 30-3500 of age in subset of this larger group, including 52 monkeys exposed to vehicle or lead during development according to one of four regimens: vehicle, lead from birth onward, lead to 400 days of age, or lead beginning at 300 days of age. No effect of lead on body weight was found. These results suggest that lead exposure beginning early in life and continuing for as long as 14 years resulted in no overt toxicity, as measured by these parameters.     

Clinical studies on multiple sclerosis

Nursery-reared rhesus monkeys were treated with no (n = 4) or moderate levels of lead (n = 4) during the first postnatal year. Mean blood lead levels peaked at 55 micrograms/dl at 5 weeks of age, averaged 36 micrograms/dl for the remainder of the first year postpartum, and declined to < or = 5 micrograms/dl for the 4 monkeys by 2.3 years of age. Previously, the lead-treated monkeys exhibited increased environmental exploration and decreased inactivity in a nonhuman primate version of the open field when tested at 4, 5, and 6 years of age (5,6). The current study was designed to assess behavior in the home cage of these monkeys at 6 years of age to determine: (a) whether the increased exploration was specific to the open field, and (b) any lead-related behavioral alterations specific to the home cage. Each monkey was observed twice weekly for 10 weeks and the duration and frequency of 17 behaviors were recorded. Lead treatment did not result in significant alterations in any of the six behaviors which occurred with enough frequency to warrant analysis. As a whole, all monkeys were either inactive or engaged in self-grooming for a large proportion of the test session. Less frequent were behaviors such as locomotion, environmental exploration, and self-directed behaviors. The distribution of behavioral activities in the home cage differed from that in the open field. Potential reasons for the expression of significant lead-related effects in the open field and not in the home cage are discussed as well as the differences in distribution of behavioral activities.     

Hemorheology in occupational lead exposure

OBJECTIVES: The purpose of this investigation was to study hemorheological parameters in occupationally lead exposed men. MATERIAL AND METHODS: For 15 clinically healthy lead-exposed male subjects [age 34.6 (SD 8) years] the viscous (epsilon') and elastic (epsilon") components of whole blood viscosity corrected for 45% hematocrit were measured for shear rates between 1.s-1-100.s-1 at 37 degrees C. Moreover, lead concentrations in blood and urine and the delta-aminolevulinic acid dehydrase level were determined. Fifteen unexposed age-matched men were used as referents. RESULTS: The mean lead concentration in the blood and urine of the lead-exposed men was 48.7 (SD 16.2) micrograms. dl-1 and 38.8 (SD 17.1) micrograms.g creatinine-1, respectively. While epsilon" was significantly increased only at low shear rates, epsilon' was elevated throughout the investigated shear range in comparison with the values of the unexposed referents. These results are characteristic of erythrocytes with enhanced rigidity. The aggregation and filtration index of erythrocytes were significantly elevated for the lead-exposed workers. A positive correlation existed between lead in blood and epsilon' or epsilon", whereas delta -aminolevulinic acid dehydrase and epsilon' or epsilon" were inversely correlated. No differences in plasma viscosity or in lipid status could be detected. CONCLUSION: Increased blood lead concentrations can be considered an additional risk factor for vascular diseases predisposing towards microvascular occlusion.     

Childhood lead poisoning in Asturias

We have determined the blood lead levels of 1,242 children, from newborn to 14 years old, and 79 young mothers in a period of 10 months in Asturias (Spain). All of them were selected at random among those who consulted one of the three main hospitals in Asturias, but none were diagnosed as lead poisoning. We have found a mean blood lead level of 22.11 micrograms/dl; 23.55% had high levels (= 25 micrograms/dl). Sex was not significantly associated with blood lead levels either in the whole sample or in different age groups. Blood lead level increases rapidly from birth (19.3 micrograms/dl) to the age of one year (23.3 gamma/dl), fluctuating around this level until the age of 7. Then it declines with age until adolescence (19.6 micrograms/dl). From October (25.5 micrograms/dl) to July (20.9 micrograms/dl) the decrease in lead blood level was statistically significant. No difference has been found between urban and rural population. The decree of urbanization has not been found significant. The mean blood lead level in the mothers was 20.5 micrograms/dl.     

Effect of occupational lead exposure on immunoglobulin concentration and cellular immune function in man

The evaluation of immunological conditions of 14 workers occupationally exposed to lead and the comparison of these results with those of a non-exposed control group with similar age and sex were the aims of this study. It was determined the mean values of lead in blood. In exposed workers it was 46.9 micrograms/dl while in the control group it was 10.9 micrograms/dl. Levels of immunoglobulin decreasing while increasing lead concentration in blood were found in those exposed. It was also found a significant decrease in the formation for rosette in relation to the control group.     

Exposure to lead among the population of Barcelona: chronologic trends from 1984 to 1995

BACKGROUND: This study was designed to determine current lead exposure in the Barcelona population and to evaluate the changes occurred during the last 10 years. Blood lead concentration was investigated in a random sample of 694 healthy subjects (age range: 0-65 years). PATIENTS AND METHODS: Adults were random selected from a group of blood donors. Samples of children analysed were selected from subjects with a preoperatory analyses without any disease that could modify blood lead levels. Lead levels were determined by atomic absorption spectrometry. RESULTS: Blood lead concentration was 4.06 +/- 1.4 micrograms/dl in umbilical cord, 8.9 +/- 2.9 micrograms/dl in the paediatric population and 7.8 +/- 4.2 micrograms/dl in the total of adults analyzed. There was statistical differences between the younger subjects and the older population. In 1984 the results found were 18.6 +/- 6.6 micrograms/dl. CONCLUSIONS: The results obtained show that in the last 10 years a reduction on the blood lead levels was occurred. This reduction is parallel with a diminish in the lead petrol concentration in the ambient air.     

Blood lead levels in preschool children in Rawalpindi

Blood lead levels were determined in preschool children residing in Urban areas of Rawalpindi city. Of 92 (50 males and 42 females) children aged one to 5 years were included in the study. Blood lead levels ranged from 7 micrograms/dl to 34 micrograms/dl (mean 18.8 micrograms/dl). The mean lead levels were slightly higher in males (20.3 micrograms/dl) than in females (17.2 micrograms/dl) and over 90% children had lead levels above the acceptable limit of 10 micrograms/dl. Use of leaded petrol, contaminated surma, leaded paints and pica in children are common in our country and may lead to increased lead levels and appropriate measures should be taken to control this trend.     

Absence of peripheral neuropathy in long-term lead-exposed subjects

The safety of a blood lead concentration of 70 microgram/100 ml as a hygienic border value with regard to development of lead neuropathy was tested in 95 employees, who had been exposed occupationally to lead for more than 9 years. The blood lead concentration was slightly above the border value in nine subjects, while the erythrocyte-Zn-protoporphyrin concentration was significantly elevated in 81 subjects, indicating an abnormal accumulation of metabolically active lead. None of the group showed clinical evidence of peripheral neuropathy, and the vibratory perception thresholds as well as motor conduction data from the median, radial, and common peroneal nerves were normal, as compared with an age-matched control group of 21 non-exposed normal subjects. The amplitude ratio between proximally and distally evoked muscle action potentials was normal in all lead-exposed subjects. These findings suggest that lead-exposed subjects are well protected against peripheral lead neuropathy, when blood lead levels are kept below the hygienic border value.     

Low-level lead exposure and children's intelligence from recent epidemiological studies in the U.S.A. and other countries to progress in reducing lead exposure and screening in the U.S.A

From the 1980s many well-designed epidemiological studies have confirmed that low-level, subclinical lead exposure in early life is associated with decrements in children's intelligence. Neurodevelopmental deficits from exposure to a low level of lead have been held to be not only an American problem, but also a worldwide issue in the past decade. Good epidemiological studies were reported from England, Scotland, Germany, Greece, Australia and New Zealand. Well-designed cross-sectional and prospective studies were carried out to quantify the magnitude of the relation between full scale IQ in children aged five years or more and the burden of lead (PbB or PbT) in early life of children. Of five cross-sectional studies of blood lead, two demonstrated a significant inverse association between lead and IQ even after adjustment for confounders. Two other studies, however, showed no firm evidence of inverse association after adjustment for confounders, and the remaining study demonstrated no significant inverse association of five cross-sectional studies of tooth lead, two indicated an inverse association between tooth lead and IQ, two others showed no significant inverse association after adjustment for confounders, and the remaining one manifested no association. Of four prospective studies, two revealed strong evidence of an inverse association between blood lead at the age of around two years and IQ. Another one, however, revealed an inverse association between mean postnatal blood level and IQ, while the remaining one demonstrated no significant inverse association between IQ and postnatal blood lead level after adjustment for confounders. In a comprehensive review of 26 epidemiological studies since 1979, including a meta-analysis, Pococok et al. indicated that doubling of the body lead burden (from 10 to 20 micrograms/dl) blood lead or (from 5 to 10 micrograms/g) tooth lead is typically associated with a mean deficit in full-scale IQ of around 1-2 IQ points. Lead in interior household dust, exterior surface soil, and old residential lead paint, which is deteriorated or removed, constitute the major sources of lead poisoning in children in the United States. Infants and children, who typically engage in hand to mouth activities, frequently come into contact with lead dust in soil and on the floor. Marked declines both in air lead and blood lead concentrations are evident parallel to the phase-down of lead in gasoline and soldered cans by U.S. food processors. The major source of lead in drinking water is from lead pipes used in household plumbing. The CDC revised its guidelines concerning childhood lead poisoning, stating that community prevention activities should be triggered when a large percentage of children in a community have blood lead levels of 10 micrograms/dl, the lowest level at which neurodevelopmental effects were believed to occur. For children with blood lead level concentrations between 10 and 14 micrograms/dl, more frequent rescreening may be needed. For concentrations between 15 and 19 micrograms/dl, in addition to more frequent screening, nutritional and educational advice should be given. In cases where these levels persist, there should be environmental investigation and intervention. All children with blood levels of 20 micrograms/dl or greater should receive environmental evaluation and medical examination. Such children may need pharmacological treatment.     

Lead exposure of workers in the ceramics industry and relevant factors

To clarify lead exposure and factors relevant to it, an occupational health survey and air lead-concentration survey were conducted among 425 workers in the ceramics industry in the Seto region in Aichi Prefecture. As for biological monitoring, blood lead level was measured according to sex, job, product, factory size and duration of lead exposure. The following major findings were obtained in the present analysis. Workers making dolomite novelties showed higher blood lead levels than those making porcelain novelties, semi-porcelain novelties and tableware. The difference in blood lead level by job was statistically significant, but not that by factory size. In males, the highest blood lead level was found for spray painting work (28.7 micrograms/dl), followed by glazing work (28.0 micrograms/dl), kiln work (23.3 micrograms/dl) and painting work (22.3 micrograms/dl). In females, the blood lead level for painting work (13.5 micrograms/dl) was lower than those for glazing work (26.1 micrograms/dl) and kiln work (31.4 micrograms/dl). The blood lead level was significantly increased with the number of years of lead exposure in females (painting work). It was coincidentally clarified that the environmental lead concentration varied according to the job in which workers were engaged. As protective measures against lead exposure for workers in the ceramics industry, the development of nonlead paint and glaze and the introduction of more effective dust collectors at the workplace should be established.     

Environmental urban lead exposure and blood lead levels in children of Mexico City

Lead contamination is now a leading public health problem in Mexico. However, there are few data on the lead content of various environmental sources, and little is known about the contribution of these sources to the total lead exposure in the population of children residing in Mexico City. We conducted a cross-sectional study in a random sample of 200 children younger than 5 years of age who lived in one of two areas of Mexico City. Environmental samples of floor, window, and street dust, paint, soil, water, and glazed ceramics were obtained from the participants' households, as well as blood samples and dirt from the hands of the children. Blood lead levels ranged from 1 to 31 micrograms/dl with a mean of 9.9 micrograms/dl (SD 5.8 micrograms/dl). Forty-four percent of the children 18 months of age or older had blood lead levels exceeding 10 micrograms/dl. The lead content of environmental samples was low, except in glazed ceramic. The major predictors of blood lead levels were the lead content of the glazed ceramics used to prepare children's food, exposure to airborne lead due to vehicular emission, and the lead content of the dirt from the children's hands. We conclude that the major sources of lead exposure in Mexico City could be controlled by adequate public health programs to reinforce the use of unleaded gasoline and to encourage production and use of unleaded cookware instead of lead-glazed ceramics.     

Chronic exposure to environmental lead in Chilean infants

BACKGROUND: In Chile, there are several sources of environmental lead exposure. However, the few studies about lead levels in Chilean infants, do not allow to establish the prevalence of high lead levels in this population. AIM: To measure blood lead levels in nursing infants, living in rural and urban areas, from birth until two years of age. SUBJECTS AND METHODS: Newborns from public maternity hospitals in Santiago and a rural area were selected for the study. An umbilical cord blood sample was obtained at birth and venous blood samples thereafter, every 6 months until the age of 24 months. Lead levels were measured by atomic absorption spectrophotometry. Atmospheric lead was measured simultaneously every week in Santiago and the rural area. RESULTS: Three hundred twelve children from Santiago and 113 from the rural area completed the 24 months follow-up. The mean lead exposure for infants living in Santiago and in the rural area was 1.23 +/- 0.66 and 0.19 +/- 0.15 micrograms/m3 respectively (p < 0.001). Mean blood levels were always higher in infants from Santiago, compared to those from the rural area. At 24 months, 4.5% of children from Santiago and 0.7% of children from the rural area had blood lead levels over 10 micrograms/dl. Significant risk factors for high lead levels were recent painting of the house where the infant lives, eating soil, biting banisters and familiar labor exposure to lead. CONCLUSIONS: Infants living in an urban area and exposed to increased atmospheric lead levels have higher blood lead levels than infants living in a rural area.     

Non-occupational lead exposure and hypertension in northern Italy

BACKGROUND: Previous research has addressed the issue that low-level blood lead concentration could be associated with an increased risk of hypertension. METHODS: This paper examines the cross-sectional association between blood lead and hypertension in 630 adult males not employed in activities characterized by specific exposure to lead and living in two Northern Italian cities (Verona and Brescia). The participants, aged 26-69 years, constituted a random sample of the patients in the practice of a general practitioner (Verona) and of regular blood donors (Brescia). Logistic regression analysis was used to evaluate the effects of selected variables (blood lead, blood cadmium, zinc erythroprotoporphyrin, haemoglobin, whole blood viscosity, age, body mass index, smoking habits and alcohol consumption) on the probability of being hypertensive. RESULTS: The blood lead concentration (range: 4.3-46.9 micrograms/dl; median: 14.8 micrograms/dl) was very similar in the two samples, whereas the prevalence of hypertension was significantly higher in the Verona sample than in the Brescia sample (20.4% versus 8.3%). Hypertensive subjects showed significantly higher blood lead levels than normotensive ones. In a preliminary (univariate) analysis blood lead levels, body mass index (BMI) and age were each significantly related to the prevalence of hypertension. After adjusting for age and/or BMI, statistical significance of the relationship between blood lead and hypertension was lost.CONCLUSIONS. The present study showed that blood lead is weakly related to hypertension in non-occupationally exposed men. The statistical significance of this association disappeared when age and BMI were used to make adjustments.     

delta-Aminolevulinic acid in plasma or whole blood as a sensitive indicator of lead effects, and its relation to the other heme-related parameters

To evaluate the subclinical effect of lead exposure, we determined delta-aminolevulinic acid (ALA) levels in plasma (ALA-P), blood (ALA-B), and urine (ALA-U) and the activity of delta-aminolevulinic acid dehydratase (ALAD) in lead workers. Almost all of the ALA molecules in blood were present in plasma and not in blood cells, irrespective of the blood lead concentration (Pb-B). ALA-P or ALA-B levels increased slowly at Pb-B levels below 40 micrograms/dl (slow phase) and rapidly at levels above 40 micrograms/dl (rapid phase). In both phases, ALA-P and ALA-B were well correlated with Pb-B and ALAD activity. The threshold value (no-effect level) of Pb-B for elevation of the ALA-P or ALA-B level was coincident with that for ALAD inhibition; the value was around 5 micrograms/dl. In the rapid phase, ALA-P increased continuously up to 100 micrograms/dl of Pb-B, while ALAD activity reached a plateau. Receiver operative characteristic (ROC) plot analyses indicated that ALA-P and ALAD activity [ALAD(u)] had a similar diagnostic value at Pb-B levels between 10 and 40 micrograms/dl, although ALAD(%), the remaining ALAD activity as a percentage of the whole activity restored by zinc and dithiothreitol, had the most powerful diagnostic efficiency at these Pb-B levels. By contrast, ALA-U and zinc protoporphyrin were less effective for the diagnosis of lead exposure than ALAD and ALA-P. These findings indicate that ALA-P is the best discriminators of lead exposure form baseline to high levels of exposure.     

Toxoplasma gondii recombinant antigens H4 and H11: use in ELISAs for detection of toxoplasmosis in swine

The prevalence of elevated blood lead (PbB) levels in rural and semi-urban areas of Kwazulu/Natal (KZN) as well as the risk factors for elevation of PbB among children in informal settlements are examined. The study involved over 1200 children in two age groups: 3-5 and 8-10 years old. Average PbB level in Besters, an informal settlement in the Durban metropolitan region, was 10 micrograms/dl with 5% of the children showing PbB level of greater than 25 micrograms/dl. By comparison, average PbB value in Vulamehlo, a rural area located 90-120 km from Durban, was 3.8 micrograms/dl and 2% of the PbB was greater than 10 micrograms/dl. The results show that many children in KZN are at risk of being lead poisoned. Household factors that were significantly associated with PbB levels in children included distance from tarred roads, overcrowding, hygienic habits in the household and the burning of solid wastes for heating or cooking. Lack of significant association with child risk behaviors is attributed to the over-riding influence of high levels of contaminated dusts both indoor and outdoor. With recent introduction of unleaded gasoline in South Africa, a number of unique socio-ecological factors are expected to slow the change in PbB levels of children in some townships.     

Association of cumulative lead and neurocognitive function in an occupational cohort.

Lead is a neurotoxicant that accumulates in bone with a half life of 25-30 years. To evaluate the association of lead biomarkers and cognitive function, a cohort of exposed and nonexposed workers who had been previously assessed in 1982 was retested approximately 22 years later. For the current assessment, both blood lead and tibia bone lead levels were determined. In addition, cognitive function was tested with the Pittsburgh Occupational Exposures Test battery, which had previously been administered in 1982. In exposed workers, bone lead level predicted lower current cognitive performance and cognitive decline over 22 years. In those lead-exposed workers older than age 55, higher levels of bone lead predicted poorer cognitive scores, suggesting vulnerability for older workers with higher past lead exposure. Finally, there was no association with bone lead level and recency of exposure, suggesting that cumulative body burden is most likely responsible for the progressive cognitive decrement evidenced with vulnerability because of aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Subclinical vestibulo-cerebellar, anterior cerebellar lobe and spinocerebellar effects in lead workers in relation to concurrent and past exposure

By computerized static posturography, the subclinical effects of past and concurrent lead absorption on the vestibulo-cerebellum (lower vermis), anterior cerebellar lobe and spinocerebellar afferent pathway were examined in 49 male chemical factory workers exposed to lead stearate (lead workers). Their concurrent blood lead (BPb) concentrations ranged from 7 to 36 (mean 18.0) microgram/100 g. In the past, their maximum BPb ranged from 11 to 113 (mean 47.7) micrograms/100 g; mean BPb was 7-52 (mean 23.5) micrograms/100 g; and cumulative BPb, defined as mean BPb x years of exposure, was 15-1268 (mean 390.6) micrograms.year/100 g. Control subjects were 23 healthy male workers who had never been occupationally exposed to lead. The postural sway of high (2-4 Hz) and low (1 Hz or less) frequencies with eyes open for lead workers was significantly greater than that for controls in the medio-lateral (right-left) and anterior-posterior directions. Similarly, the sway of high and low frequencies with eyes closed was significantly larger in lead workers than in controls in the medio-lateral direction. Results of stepwise multiple regression analysis indicated that the sway with frequencies of 0.5-2 Hz with eyes open was related to concurrent BPb in the anterior-posterior direction. With eyes closed the sway of high frequency was significantly related to mean BPb in the past in the medio-lateral direction. The pattern of the changes suggests that the vestibulo-cerebellum, anterior cerebellar lobe and spinocerebellar pathway are asymptomatically affected by lead. It appears that the change in the vestibulo-cerebellum reflects concurrent lead absorption, while on the other hand, that in the anterior cerebellar lobe reflects past lead absorption.     

Iodine content in urine samples among Malays and aborigines

A study was conducted to compare the urinary iodine concentrations in populations from Pahang, Central Malaysia, with those in the capital city Kuala Lumpur, and to compare those of Malays from villages at Batu Talam, Batu Malim, FELDA Sungai Koyan and Hulu Sungai with neighboring aboriginal settlements at Lanai and Buntu. Two hundred and forty urine samples were collected randomly among the population (male 1 1 1 and female 129). The urinary iodine concentrations, measured by the ashing method, among Malays were as follows: Batu Talam 1.1-7.6 micrograms/dl, Batu Malim 1.4-6.6 micrograms/dl, FELDA Sungai Koyan 0.5-6.9 micrograms/dl and Hulu Sungai 0.6-9.9 micrograms/dl. Among aborigines, the urinary iodine levels were 0.1-2.9 micrograms/dl in Lanai and 1.7-6.5 micrograms/dl in Buntu. There was a significant difference in the levels of urinary iodine with regard to gender, but not regarding age. The aborigines had significantly lower iodine levels than Malays (P < 0.001). This difference was also significant with regard to location. The urinary iodine content in Kuala Lumpur was the highest and that in the aboriginal Lanai village was the lowest. Thus, the study showed that the levels of iodine in the urine were influenced by ethnicity and geographic location.