Add Control: plant virtualization for control solutions in WWTP.

This paper summarizes part of the research work carried out in the Add Control project, which proposes an extension of the wastewater treatment plant (WWTP) models and modelling architectures used in traditional WWTP simulation tools, addressing, in addition to the classical mass transformations (transport, physico-chemical phenomena, biological reactions), all the instrumentation, actuation and automation & control components (sensors, actuators, controllers), considering their real behaviour (signal delays, noise, failures and power consumption of actuators). Its ultimate objective is to allow a rapid transition from the simulation of the control strategy to its implementation at full-scale plants. Thus, this paper presents the application of the Add Control simulation platform for the design and implementation of new control strategies at the WWTP of Mekolalde.

Water network cost optimization in a paper mill based on a new library of mathematical models.

The increasing costs associated with water supply and the disposal of wastewater has stimulated industries to seek more efficient water management systems. Mathematical modelling and simulation can be a very valuable tool for the study of the multiple alternatives available whilst assessing optimum solutions for water management in industry. This study introduces a new steady state model library able to reproduce industrial water circuits. It has been implemented in a novel software framework for the representation, simulation and optimization of industrial water networks. A water circuit representing a paper mill has been modelled and simulated showing the capability to reproduce real case studies. Alternative scenarios for the water network have also been tested to assess the capability of the models to optimize water circuits minimizing total cost.

Hunger and negative alliesthesia to aspartame and sucrose in patients treated with antipsychotic drugs and controls.

The present study explores sweet stimuli effects on hunger and negative alliesthesia in patients treated with antipsychotic drugs and controls. Those phenomena were examined in relation to previous weight gain, eating and weight-related cognitions and type of sweet stimuli: aspartame or sucrose. Alliesthesia is delayed in participants who gained weight regardless of cross group differences. A similar reduction of hunger was observed after the intake of two kinds of sweet stimuli (aspartame or sucrose) whereas alliesthesia measures were not affected. Whereas atypical antipsychotic drug-induced weight gain is linked to delayed satiety, the phenomenon is similar in magnitude in non-psychiatric controls who gained weight.

Distributed virtual experiments in water quality management.

Since the complexity of virtual experiments (VEs) and their underlying models is constantly increasing, computational performance of monolithic software solutions is rapidly becoming insufficient. Examples of VEs are probabilistic design, model calibration, optimal experimental design and scenario analysis. In order to tackle this computational bottleneck, a framework for the distributed execution of VEs on a potentially heterogeneous pool of work nodes has been implemented. This framework was named WDVE (WEST distributed virtual experimentation) and is built on top of technologies such as C++, XML and SOAP. It was designed for stability, expandability, performance, platform-independence and ease of use. Complex VEs are most often composed of mutually independent sub-experiments, which can be run concurrently. With WDVE, a complex VE that is executed on a so-called Master machine will therefore attempt to execute its sub-experiments on Slave machines that have previously registered with the Master. The process of submitting requests for the execution of sub-experiments is transparent and involves the transfer of a description of the experiment to be executed, and the resources that are needed for the execution (i.e., model and input data). WDVE is in many ways similar to the Grid Computing paradigm, which is currently receiving widespread attention. However, WDVE is more geared towards application within the scope of water quality management.

Determinants of serum zinc in a random population sample of four Belgian towns with different degrees of environmental exposure to cadmium.

This report investigated the distribution of serum zinc and the factors determining serum zinc concentration in a large random population sample. The 1977 participants (959 men and 1018 women), 20-80 years old, constituted a stratified random sample of the population of four Belgian districts, representing two areas with low and two with high environmental exposure to cadmium. For each exposure level, a rural and an urban area were selected. The serum concentration of zinc, frequently used as an index for zinc status in human subjects, was higher in men (13.1 mumole/L, range 6.5-23.0 mumole/L) than in women (12.6 mumole/L, range 6.3-23.2 mumole/L). In men, 20% of the variance of serum zinc was explained by age (linear and squared term, R = 0.29), diurnal variation (r = 0.29), and total cholesterol (r = 0.16). After adjustment for these covariates, a negative relationship was observed between serum zinc and both blood (r = -0.10) and urinary cadmium (r = -0.14). In women, 11% of the variance could be explained by age (linear and squared term, R = 0.15), diurnal variation in serum zinc (r = 0.27), creatinine clearance (r = -0.11), log gamma-glutamyltranspeptidase (r = 0.08), cholesterol (r = 0.07), contraceptive pill intake (r = -0.07), and log serum ferritin (r = 0.06). Before and after adjustment for significant covariates, serum zinc was, on average, lowest in the two districts where the body burden of cadmium, as assessed by urinary cadmium excretion, was highest. These results were not altered when subjects exposed to heavy metals at work were excluded from analysis.

Health effects of environmental exposure to cadmium: objectives, design and organization of the Cadmibel Study: a cross-sectional morbidity study carried out in Belgium from 1985 to 1989.

Cadmium is a cumulative environmental pollutant. For the general population mainly exposed by the oral route and through tobacco smoke inhalation, the kidney is the critical organ. Belgium is the principal producer of cadmium in Europe, and certain areas of the country are polluted by cadmium mainly because of past emissions from nonferrous industries. Preliminary studies carried out in one polluted area have suggested that environmental pollution might lead to an increased uptake of cadmium by the human body and possibly to health effects. Thus, a large-scale morbidity study has been initiated to assess the validity of this hypothesis. The present paper describes the protocol of this study. Its main objectives are to determine to what extent environmental exposure to cadmium resulting from industrial emissions may lead to accumulation of the metal in the human organism; to establish whether or not environmental exposure may induce renal changes and/or influence blood pressure; and to assess the acceptable internal dose of cadmium for the general population. The study design takes advantage of the fact that biological indicators of exposure, body burden, and early nephrotoxic effects of cadmium are available, which increase the likelihood of detecting a cause-effect relationship.

The association between blood pressure, calcium and other divalent cations: a population study.

This report investigated the associations between blood pressure and the levels of various divalent cations in blood and urine in the population at large. The 1,982 participants (963 men and 1019 women; mean age 48 years) constituted a stratified random sample of the population of 4 Belgian districts. Systolic/diastolic pressure averaged 133/78 mmHg in men, and 128/76 mmHg in women. Serum total calcium (2.37 mmol/l), serum magnesium (1.00 mmol/l) and blood cadmium (10.0 nmol/l) were on average similar in the two sexes. By contrast, serum zinc (13.1 and 12.6 mumol/l, respectively), blood lead (0.56 and 0.36 mumol/l) and the urinary excretions of calcium (4.86 and 3.95 mmol/24h), copper (0.16 and 0.13 mumol/24h), and cadmium (9.4 and 7.2 nmol/24h) were significantly higher in men than in women. After adjustment for significant blood pressure covariates (age, body mass index, pulse rate, log gamma-glutamyltranspeptidase, smoking habits, and in women the contraceptive pill), serum total calcium was independently and positively correlated with systolic pressure in both sexes, and with diastolic pressure in women. After similar adjustments systolic pressure was positively correlated with urinary copper in men and women. In addition, systolic pressure and blood lead, and diastolic pressure and urinary cadmium were negatively correlated in men. In conclusion, this population study demonstrated a positive relationship between systolic blood pressure and both serum total calcium and urinary copper.

Decrease in blood cadmium levels over time in Belgium.

During the time period from 1984 to 1988, blood cadmium concentration decreased by 56% in 31 males who were not occupationally exposed to cadmium and who lived in a Belgian urban area where there existed nonferrous industries. A 40% decrease in blood cadmium concentration was also observed in an independent cross-sectional survey conducted in 1985 and 1988 among 412 subjects who lived in a rural area. This latter decrease persisted when the main determinants of blood cadmium concentration--gender, age, and tobacco--were allowed for. The results presented are consistent with a decrease in environmental cadmium exposure in Belgium.

Impact of environmental cadmium pollution on cadmium exposure and body burden.

The body burden of cadmium, as estimated from 24-h urine cadmium levels, was determined in 1,523 subjects who were not occupationally exposed and who lived in five areas of Belgium. Urinary cadmium levels differed significantly with place of residence. These differences persisted after standardization for the other significant determinants (i.e., age, body mass index, smoking habits, social class, alcohol consumption, and menopause). The highest 24-h urine cadmium levels were found in subjects who lived in areas that contained cadmium-polluted soils. The body burden overload has been attributed mainly to the consumption of locally grown vegetables and the use of contaminated well water for cooking and drinking. Blood cadmium levels were also dependent on place of residence. However, the geographical differences in blood cadmium did not parallel those of urine cadmium. Blood cadmium is more influenced by recent exposure; therefore, this latter observation might reflect the recent implementation of preventive measures in some areas.

Chronic lead exposure and pregnancy.

The objective of the study was to determine the effect of chronic lead exposure on pregnancy and the newborn. Cord blood was assayed for blood lead levels (PbB) in a randomly selected group of 82 Maltese newborns. Twenty-eight (34.1%) neonates had a PbB level greater than 200 µg/l. Two trends appeared with increasing blood lead levels suggesting a decrease in newborn birth weight (r=-0.1445, P=0.207) and an increase in the duration of the first stage of spontaneous labour (r=0.1385, P=0.3043). There appeared to be no mean differences in maternal third trimester haemoglobin, duration of gestation, and previous pregnancy loss in infants with high PbB levels compared to infants with low PbB. Through its properties of inhibiting enzymatic function and its competitiveness with other minerals, calcium and zinc, chronic sub-toxic lead exposure during pregnancy may cause adverse effects on the neonate and pregnancy.

Lowering time trend of blood lead levels in Belgium since 1978.

Since 1978, the biological screening of the Belgian population was regularly monitored by measuring blood lead levels. Over 11 years, 6070 samples were analyzed in urban, rural, and industrial areas. The median values of blood lead concentration dropped from 170 to 78 micrograms/liter of blood, i.e., a lowering of about 55%. The trend persists when taking into account some individual characteristics which influence blood lead levels such as gender, age, tobacco, and areas. These influences and the possible environmental causes of the observed trend are discussed.

Analytical quality control of cadmium and lead in blood and cadmium in urine: results of its implementation during a five-year epidemiological study.

Quality-control programmes are very important in assessing the reliability of biological analyses. Such programmes are essential if misleading results in epidemiological studies dealing with low levels of exposure to heavy metals present in the general environment (e.g., cadmium, lead) are to be avoided. Internal and external quality-control programmes for the measurement of cadmium and lead in blood and of cadmium in urine were implemented from 1985 to 1989 in support of a national epidemiological study, Cadmibel (2327 participants), conducted in Belgium to assess the effects of environmental exposure to cadmium and lead on the general population. Apart from these programmes, inter-comparisons between the two participating laboratories were carried out on 10% of the samples. The results of these quality-control programmes met external acceptability criteria, emphasizing the analytical proficiency of these measurements at the relatively low concentrations in the Cadmibel study.

Factors influencing the cadmium body burden in a population study.

The cadmium body burden, as estimated from 24-h urinary cadmium (Cd-U), was determined in 1523 non-occupationally exposed subjects living in five areas of Belgium. It increased with age until 55-65 years in both sexes and thereafter decreased slightly. It was higher in smokers but was inversely associated with alcohol consumption and social class. In men only, it was also positively correlated with body mass index. After the menopause, women showed a significant increase in 24-h Cd-U independently of the other factors. In addition, the cadmium body burden was independently associated with place of residence in both sexes. Highest levels of Cd-U were found in subjects living in an area with soils heavily polluted by cadmium.

Renal effects of cadmium body burden of the general population.

In a cross-sectional population study to assess whether environmental exposure to cadmium is associated with renal dysfunction, 1699 subjects aged 20-80 years were studied as a random sample of four areas of Belgium with varying degrees of cadmium pollution. After standardisation for several possible confounding factors, five variables (urinary excretion of retinol-binding protein, N-acetyl-beta-glucosaminidase, beta 2-microglobulin, aminoacids, and calcium) were significantly associated with the urinary excretion of cadmium (as a marker of cadmium body burden), suggesting the presence of tubular dysfunction. There was a 10% probability of values of these variables being abnormal when cadmium excretion exceeded 2-4 micrograms/24 h. Excretion reached this threshold in 10% of non-smokers. There was also evidence that diabetic patients may be more susceptible to the toxic effect of cadmium on the renal proximal tubule.

Blood pressure, the prevalence of cardiovascular diseases, and exposure to cadmium: a population study.

In a population study conducted from 1985 to 1989 in Belgium, the authors investigated whether exposure to cadmium is associated with blood pressure elevation and with an increased prevalence of cardiovascular diseases. The participants, aged 20-88 years, constituted a random sample of the households living in two low exposure areas (n = 803) and two high exposure areas (n = 1,283). For each exposure level, a rural and an urban district were selected. The cadmium levels in blood (8.5 vs. 11.0 nmol/liter) and urine (7.2 vs. 8.7 nmol/24 hours) were significantly (p less than 0.001) raised in the two high exposure areas compared with the two low exposure areas (p less than 0.001). Systolic pressure was similar in both rural areas, but in the urban area with high exposure systolic pressure was 5 mmHg (p less than 0.001) higher than in the control town. Diastolic pressure was similar in the four districts and the same was true for the prevalence of hypertension and of other cardiovascular diseases. Adjustment of systolic pressure for blood and urinary cadmium did not remove the difference in systolic pressure between both urban areas, suggesting that it was not related to the cadmium burden on the environment. Further analyses in individual subjects showed that neither blood pressure nor the presence of cardiovascular diseases were significantly and positively correlated with blood and urinary cadmium. Thus, the present population study did not confirm the hypothesis that increased exposure of the population to cadmium is associated with blood pressure elevation and with a higher prevalence of cardiovascular diseases.

Does environmental exposure to cadmium represent a health risk? Conclusions from the Cadmibel study.

Cadmium is a very dispersive pollutant which has progressively accumulated in the environment mainly in the areas where nonferrous smelters have been in operation. An important toxicological feature of cadmium is its exceptionally long biological half-life in the human body. For the general population mainly exposed to cadmium by the diet and smoking, the kidney is the main target organ. Some studies have also suggested that cadmium might play a role in the pathogenesis of hypertension. A cross-sectional study (called Cadmibel) was undertaken to assess whether environmental pollution by cadmium in Belgium might represent a health risk. This paper does not present the detailed results of this study which are published elsewhere but simply report its main conclusions. A total number of 2327 subjects (stratified according to age and sex) was randomly sampled in two urban (Liège and Charleroi) and two rural (Hechtel-Eksel and Noorderkempen) areas, with different environmental pollution by cadmium. After allowing for the various factors known to influence cadmium accumulation, it was estimated that the cadmium body burden of the residents of the most polluted district (Noorderkempen) was 50 to 85% higher than in the less polluted areas. No statistical association was found between environmental exposure to cadmium and blood pressure elevation or the prevalence of cardiovascular diseases. However, the study has shown that the environmental exposure of the general population to cadmium may induce slight renal tubular dysfunction and may probably also affect cadmium homeostasis. The probability of tubular dysfunction (as assessed by sensitive tests) is about 10% when cadmium in urine reaches 2 micrograms/day. The morbidity associated with the changes in the renal proximal tubule and the calcium metabolism observed when the body burden of cadmium exceeds this value remains to be assessed.

Effects of exposure to cadmium on calcium metabolism: a population study.

The objective was to investigate the hypothesis that environmental exposure to cadmium may affect calcium metabolism in the population at large. The 1987 participants (965 men and 1022 women), from 20 to 80 years old, constituted a random sample of the population of four Belgian districts. The urinary excretion of cadmium, a measure of lifetime exposure, averaged 9.3 nmol/24 h in men (range 0.4-324 nmol/24 h) and 7.1 nmol/24 h (range 0.1-71 nmol/24 h) in women. Serum alkaline phosphatase activity and the urinary excretion of calcium correlated significantly and positively with urinary cadmium excretion in both men and women, and serum total calcium concentration negatively with urinary cadmium excretion in men only. The regression coefficients obtained after adjustment for significant covariates indicated that when urinary cadmium excretion increased twofold, serum alkaline phosphatase activity and urinary calcium excretion rose by 3-4% and 0.25 mmol/24 h respectively, whereas in men serum total calcium concentration fell by 6 mumol/l. After adjustment for significant covariates the relation between serum total calcium concentration and urinary cadmium excretion was not significant in women. The findings suggest that even at environmental exposure levels calcium metabolism is gradually affected, as cadmium accumulates in the body. The morbidity associated with this phenomenon in industrialised countries remains presently unknown and requires further investigation.

Effects of cadmium exposure on the cardiovascular system and on calcium metabolism: results of a cross-sectional population study.

This paper summarizes the findings of the Cadmibel Study, a cross-sectional population study of the health effects of cadmium, but only with respect to the cardiovascular system and calcium metabolism. The study disproved the hypothesis that exposure to cadmium would lead to an increase in blood pressure and in the prevalence of hypertension and other cardiovascular diseases. On the other hand, there was a positive relationship between urinary cadmium (Cd-U) and both serum alkaline phosphatase activity and urinary excretion of calcium. The regression coefficients obtained after adjustment for significant co-variates indicated that, when Cd-U increased two-fold, serum alkaline phosphatase and urinary calcium rose by 4% and 0.25 mmol/24 h, respectively. These findings suggest that calcium metabolism is gradually affected as cadmium accumulates in the body. The morbidity associated with the latter phenomenon is still unknown, and requires further investigation, preferably in a longitudinal prospective population study, in which the incidence of morbid events would be monitored in relation to the cadmium body burden.

Transfer of cadmium from a sandy acidic soil to man: a population study.

This population study included 230 subjects (age range 20-83 years) who consumed vegetables grown in kitchen gardens on a sandy acidic soil (mean pH approximately 6.3). The study investigated the association between the Cd (cadmium) levels in blood and urine and the Cd concentration in the soil (range 0.2-44 ppm). Seventy-six subjects were current smokers and 122 participants lived in a district with known Cd pollution. Urinary Cd in the 230 subjects averaged 8.7 nmole/24 hr, (range 1.3 to 47 nmole/24 hr) after age adjustment positively correlated with the Cd level in the soil; a twofold increase of the Cd concentration in the soil was accompanied by a 7% rise in urinary Cd in men (R2 = 0.05; P = 0.04) and by a 4% rise in women (R2 = 0.02; P = 0.05). Blood Cd averaged 11.5 nmole/liter (range 1.8-41 nmole/liter) and was negatively associated with the Cd level in the soil. After adjustment for significant covariates (smoking and serum gamma-glutamyl transpeptidase in both sexes, and age and serum ferritin in women), a twofold increase in the Cd concentration in the soil was accompanied by a 6% decrease in blood Cd in men (R2 = 0.03; P = 0.09) and by a 10% decrease in women (R2 = 0.06; P less than 0.01). In conclusion, in a rural population, consuming vegetables grown on a sandy acidic soil, 2 to 4% of the variance of urinary Cd was directly related to the Cd level in the soil. The negative correlation with blood Cd, a measure of more recent exposure, was biased by the implementation of preventive measures in the polluted district.