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Latent inhibition and perceptual learning in a swimming-pool navigation task.
In each of 3 experiments, rats were preexposed to the 4 distinct landmarks surrounding a circular pool before being trained to find a submerged platform located in a fixed position in the pool. When preexposure was to pairs of adjacent landmarks, it consistently retarded subsequent learning (a latent inhibition effect). When preexposure was to 1 landmark at a time, then, provided the 4 landmarks all contained a salient feature in common, preexposure facilitated subsequent learning (a perceptual learning effect). The results provide little support for the notion of a cognitive map and are quite consistent with an associative analysis.
An outbreak of aseptic meningitis due to echovirus 30 associated with attending school and swimming in pools.
OBJECTIVES: To identify the risk factors of an outbreak of meningitis associated with echovirus 30-infection that occurred in Rome, Italy, in late 1997 among children from two different schools. METHODS: A case-control study was carried out. A case was defined as a child from either of the two schools, A or B, who presented meningitis-like (fever, headache and vomiting), diarrhea, or respiratory tract symptoms. All asymptomatic students were included in the analysis as controls. RESULTS: Among 446 pupils (80%) who answered the questionnaire, 68 met the case definition. Twenty pupils developed a meningitis-like illness. Echovirus 30 was isolated from cerebrospinal fluid (CSF) in four and from stools in six. Forty-eight pupils reported other symptoms. The attack rate was 10.8% in school A and 0.8% in school B for meningitis-like illness; it was 12% and 10%, respectively, for other enterovirus-like illnesses. The risk of meningitis-like illness was higher among children attending school A (crude OR = 14.9; 95% CI = 4.3-52.1), among children using any public pool (OR = 3.8; 95% CI = 1.5-9.9) and those using an outside swimming pool X (OR=13.4; 95% CI=2.7-65.8 versus no swimming pool and OR = 8.3; 95% CI = 1.1-62.6 versus other pools). The epidemic curve appears to suggest a person-to-person transmission. CONCLUSIONS: The epidemic occurred by person-to-person transmission in a number of classrooms and at swimming pool X.
Disinfection by-products and microbial contamination in the treatment of pool water with granular activated carbon.
For swimming pools, it is generally agreed that free chlorine levels have to be maintained to guarantee adequate disinfection. Recommended free chlorine levels can vary between 0.3 and 0.6 mg/L in Germany and up to 3 mg/L in other countries. Bathers introduce considerable amounts of organic matter, mainly in the form of such as urine and sweat, into the pool water. As a consequence, disinfection byproducts (DBPs) are formed. Regulations in Germany recommend levels of combined chlorine of less than 0.2 mg/L and levels of trihalomethanes (THMs) of less than 20 microg/L. Haloacetic acids (HAAs), haloacetonitriles (HANs), chloropicrin and chloral hydrate are also detected in considerable amounts. However, these compounds are not regulated yet. Swimming pool staff and swimmers, especially athletes, are primarily exposed to these byproducts by inhalation and/or dermal uptake. In Germany, new regulations for swimming pool water treatment generally require the use of activated carbon. In this project, three different types of granular activated carbon (GAC) (one standard GAC, two catalytic GACs) are compared for their long time behaviour in pool water treatment. In a pilot plant operated with real swimming pool water, production and removal of disinfection byproducts (THMs, HAAs, AOXs), of biodegradable substances (AOC), of bacteria (Pseudomonas aeruginosa, Legionella, coliforms, HPC) as well as the removal of chlorine and chloramines are monitored as function of GAC bed depth. Combined chlorine penetrates deeper in the filter bed than free chlorine does. However, both, free and combined chlorine removal efficiencies decrease over the time of filter operation. The decreases of removal efficiencies are also observed for parameters such as dissolved organic carbon, spectral absorption coefficient, adsorbable organic carbon and most of the disinfection byproducts. However, THMs, especially chloroform are produced in the filter bed. The GAC beds were contaminated microbially, especially with P. aeruginosa. The contamination was not removable by backwashing with chlorine concentrations up to 2 mg/l free chlorine.
[Epidemiology of free-living amoebae in the waters of Strasbourg (France) (author's transl)].
164 strains of free-living amoebae were isolated from public drinking water supplies, swimming pools and official swimming ponds in Strasbourg; 11 genera and 16 species were identified. Some strains of Acanthamoeba are pathogenic for mice by intracerebral inoculation. Among the two strains of Naegleria found none is pathogenic. The results concerning free-living amoebae are compared with the level of chlorine and bromine and with the presence of bacteria in swimming pools.
Drowning mortality in Los Angeles County, 1976 to 1984.
Drowning is the fourth leading cause of unintentional injury death in Los Angeles County. We examined data collected by the Los Angeles County Coroner's Office on drownings that occurred in the county from 1976 through 1984. There were 1587 drownings (1130 males and 457 females) during this nine-year period, for an annual rate of 2.36 drownings per 100,000 persons (3.44 for males and 1.33 for females). The largest proportion of drownings (44.5%) for both sexes, and in almost every age group, occurred in private swimming pools. Children 2 to 3 years of age had the highest swimming-pool drowning rate (7.95). The elderly also experienced high drowning rates, primarily in swimming pools and bathtubs. Drowning-site profiles varied dramatically by age and sex. These findings indicate a need for Los Angeles County to address the problem of drownings among infants and toddlers in private swimming pools and to investigate the failure of regulations requiring fencing of swimming pools to prevent these deaths. These findings also suggest several potential opportunities for preventive intervention by physicians and demonstrate that health professionals cannot rely on national drowning-site profiles when developing local drowning prevention strategies.
Pharyngoconjunctival fever caused by adenovirus type 4: report of a swimming pool-related outbreak with recovery of virus from pool water.
During the summer of 1977, an outbreak of pharyngoconjunctival fever (PCF) occurred at a private recreational facility in Georgia. A total of 72 cases of PCF was identified. Adenovirus type 4 (AV-4) was recovered from conjunctival or pharyngeal swab specimens from 20 of 26 persons in the group of cases tested. AV-4 was also recovered, for the first time reported in the literature, from two concentrated samples of water obtained from the swimming pool at the facility on different dates. All persons affected had had direct or indirect contact with the pool. A linear relation between the amount of time spent in the water and the attack rate was demonstrated (r = 0.929, P less than 0.01). Investigation showed that inadequate amounts of chlorine had been added to the pool water. Frequently, levels of free chlorine were below the recommended level of 0.4 mg/liter. Breakpoint chlorination and closing of the pool for the summer stopped the spread of PCF.
Assessment of chlorine exposure in swimmers during training.
The presence of a high prevalence of bronchial hyperresponsiveness and asthma-like symptoms in swimmers has been recently reported. Chlorine, a strong oxidizing agent, is an important toxic gas that the swimmer can breath during swimming. Measurements of the chlorine concentration at the breathing level (< 10 cm) were obtained randomly during five nonconsecutive days in four different swimming pool enclosures. The mean level in all the swimming pools was 0.42 +/- 0.24 mg.m-3, far below the threshold limited value (TLV) of 1.45 mg.m-3 for the work places for a day of work (8 h). The TLV could be reached and even exceeded if we consider the total amount of chlorine that a swimmer inhales in a daily training session of 2 h (4-6 g) compared with a worker during 8 h at the TLV (4-7 g). Low correlation was observed with the number of swimmers in the swimming pool during the measurements (0.446) and other variables as the water surface area of the pool, volume of the enclosure, and the chlorine-addition system in the swimming pool. A low turnover rate in the air with an increase of chlorine levels through the day (P < 0.05) was observed in all pools. The concentration of chlorine in the microenvironment where the swimmer is breathing is below the TLV concentration limit, but nevertheless results in a high total volume of chlorine inhaled by the swimmers in a given practice session. The possible role of chlorine in producing respiratory symptoms in swimmers needs further investigation.
Childhood drownings and fencing of outdoor pools in the United States, 1994.
OBJECTIVES: To determine the prevalence of proper fencing around outdoor swimming pools among US households and to describe this fencing in relation to demographic and other household factors. To estimate the number of drownings among children <5 years of age that might be prevented by having proper fencing around all residential pools in the United States. METHODS: A 1994, randomly dialed national telephone survey contacted 5238 adults who reported demographic information and household characteristics including whether the household had an outdoor swimming pool and the fencing around the pool. Data were weighted to obtain national estimates and percentages. The number of preventable drownings was estimated with a population-attributable risk equation. RESULTS: Approximately 18.5 million American households owned or had access to an outdoor swimming pool in 1994, and 76% (13.9 million) of them appeared to have had adequate fencing. Adequate fencing was associated with household income and type of home. We estimate that 19% of pool-related drownings among children <5 years of age in 1994 (88 drownings) might have been prevented if all residential pools in the United States were properly fenced. CONCLUSIONS: Adequate pool fencing prevents a child from having access to a swimming pool if a responsible adult is not present and has been promoted as a method to prevent drowning. Our research suggests that even if all residential pools in the United States were properly fenced, most drownings among children <5 years of age would not be prevented. Thus, additional strategies to prevent drowning will be needed.
Climbing performance of children: is the above-ground pool wall a climbing barrier?
15 children between the ages of 42 and 54 months attempted to climb a 48-in. wall representing the wall of an above-ground swimming pool. Three different climbing tasks were presented to all the children: (1) climbing over the swimming pool wall without any tools which could assist their climb, (2) climbing over the wall with a child-resistant ladder frame placed over the wall, (3) climbing over the wall when a pool filter was placed 12 in. from the wall. Each child's success or failure climbing over the pool wall was recorded. A repeated-measures analysis of variance indicated there were no significant performance differences in performance across the three climbing tasks. None of these climbing tasks resulted in more successful climbing performances for all the children. The results of these observations indicated the removal of the swimming pool filter or support frame of the ladder did not always stop the children from climbing over the wall. Since the 48 in. wall of the home swimming pool does not consistently function as a barrier, additional fencing is needed to prevent children from entering above-ground home swimming pools. However, no barrier replaces constant supervision of young children.
Molluscum contagiosum, swimming and bathing: a clinical analysis.
The link between swimming and bathing behaviour, and molluscum contagiosum (MC), in a sample of 198 patients with clinically confirmed MC was investigated. Results show that of all the swimming behaviour variables tested, only one (swimming in a school swimming pool) was significant. In relation to the bathing variables tested, only two (sharing a bath sponge with a MC-infected person, and sharing a bath towel with a MC-infected person), were significant. No relationship was found between MC and swimming in a private (home) pool, swimming in a public pool, swimming at the beach, sharing a bath tub with a MC-infected person, and using a private (home) spa. The Relative Risk (RR) ratio of a person sharing a bath sponge with an infected person is three times more at risk of procuring a severe case of MC infection (i.e. > 26 lesions) than a person who does not share a bath sponge with an infected person (r = 0.5; P < 0.01). There was a correlation found between the mode of MC acquisition by site location (r = 0.63; P < 0.05). The anatomical position of MC lesions was shown to be highly dependent on the way the patient was primarily infected. There was also an additive effect with the mode of transmission in that patients who were in the upper extremes in terms of the total number of lesions (average, 124 lesions; mean diameter size, 4.2 mm; n = 42), were those patients who shared a number of fomites (bath sponge, bath towel) with a known MC-infected person, and also swam at the school swimming pool.
[Haloforms in hot spring pools].
Chloroforme is formed during disinfection of swimming pool water in certain amounts depending on several cofactors. Because of its carcinogenic properties this compound has been frequently a subject of public discussion over the last couple of years. Little is known about chloroforme concentrations in spas. Spas are operated at significantly higher temperatures as compared to other pools, and the organic contamination may be higher. Therefore, chloroforme is possibly produced in higher amounts than in regular swimming pools. On the other hand the air that is blown through the bassin may reduce the concentration of this low volatile substance. In order to investigate the average concentration, 21 water samples from spas in public indoor pools were analyzed as to their chloroforme contend. The median of concentration was 3.8 micrograms/l. The maximum measured chloroforme concentration was 6.4 micrograms/l. The average chloroforme concentration in the filtered water was slightly higher than before filtration. The use of spas does not implicate an increase in chloroforme uptake by bathers.
Sources of variability in levels and exposure to trihalomethanes.
In the framework of a cohort study of pregnant women conducted in Brittany (France), we assessed the exposure to trihalomethanes (THM) during pregnancy in a subset by evaluating (1) potential sources of variability in household THM levels; (2) the between- and within-subject variability in THM levels; (3) THM levels in swimming pools; and (4) the role of water-related habits on total THM uptake. We visited 109 women from the ongoing cohort study at home for an interview and collection of tap water from October to December 2004. Forty-three of them were re-contacted to obtain a second tap water sample in April-May 2005. We designed a questionnaire to collect individual information on source and amount of drinking water, frequency of showering, bathing, and swimming pool attendance, and household characteristics. We obtained 282 THM measurements, 152 specifically for the study and 130 from a regulatory agency. Personal information and environmental data were combined using two methodologies (method 1 using regulatory data and method 2 using our THM measurements) with a different set of assumptions. We calculated ingestion, showering, bathing, and swimming pool THM uptakes and added up those uptakes to calculate total THM uptake. Average THM levels from our measurements in October, November-December, and April-May were 61.3, 45.1, and 54.5 microg/l, respectively. Geographical variability was low and characteristics of the household did not influence THM levels. Within-subject variability in THM levels was three times higher than between-subject variability. Average THM level in swimming pools was 80.4 microg/l. Average water consumption during pregnancy was 1.9l/day. The source of the household drinking water was 90% bottled, 8% municipal, and 2% from other sources. Forty-seven per cent attended swimming pools during pregnancy. Using method 1, the geometric mean of total THM uptake was 0.93 microg/day. Showering contributed 64%, swimming in pools 23%, bathing 12%, and drinking water 1% to the total THM uptake. In a setting with low geographical variability and limited environmental measurements, individual data is highly relevant to determine personal THM exposure and uptake. In a population that mainly drinks bottled water (e.g., pregnant women), individual THM uptakes are dominated by inhalation and dermal absorption during, showering, swimming in pools, and bathing.
[Viral pollution studies of water environments].
Virus pollution was studied in 734 water samples collected from the Dîmboviţa River (310), lakes inside the town of Bucharest (136) and swimming pools (288). The results showed that the works carried out these last years to regularize the Dîmboviţa led to a reduction of the virus pollution rate from 16.6-26.9% in 1984 to 4.16-5% in 1988. As for the lake and swimming pool waters, the pollution rate is directly proportional to the applied general hygiene measures. In summer, in drained lakes strictly controlled from the domestic and industrial sewage discharge point of view, the pollution rate was no higher than 6%, while in the lakes receiving sewage the frequency of isolations was between 12.5 and 18.75%. The same situation was found for swimming pools. A microepidemics of blepharoconjunctivitis was recorded in 1988 at a sport base: viruses were isolated from 20% of the water samples collected from its swimming pool, while virus pollution was about zero in the swimming pool water of some big hotels in Bucharest.
A primary school outbreak of pharyngoconjunctival fever caused by adenovirus type 3.
High rates of absenteeism in a North Queensland primary school, due to eye irritation, fever, headache, and stomach pain, were reported to the Tropical Public Health Unit in October 2000. Subsequent investigation demonstrated that the symptoms were due to adenovirus infection. Symptoms were consistent with a diagnosis of pharyngoconjunctival fever. At the height of the outbreak, about 40 per cent of students were absent. There was a strong association between the development of symptoms, and having been swimming on a recent school camp. Adenovirus could not be isolated from swimming pool water from the resort where the camp had been held. However, when inspected the swimming pool was not adequately chlorinated or maintained. It is probable that adenovirus infection was transmitted via swimming pool water at the school camp, and the outbreak might have been avoided by higher standards of swimming pool maintenance.
Of mice and mazes: similarities between mice and rats on dry land but not water mazes.
Mice are impaired relative to rats in place and matching-to-place learning when tests are given in a swimming pool. The rat advantage may stem from a superior spatial ability or from adaptation to a niche that has prepared them for competency in the water. In the present study, mice (C57BL/6) were compared with rats (Long-Evans) in a number of dry-land spatial tasks given on a radial arm maze and in a place task given in a swimming pool. The performance of the mice matched that of the rats in all dry-land tasks, but was inferior to that of the rats in the swimming pool. The results provide further evidence for a species difference in swimming-pool performance but do not support the idea that there are necessary differences in spatial abilities between mice and rats. It is suggested that, if optimal place learning is required for neurobehavioral studies of mice, such performance is more likely to be obtained in dry-land tasks than in swimming-pool tasks. Nevertheless, the species differences warrant further study because they could provide important insights into species differences is spatial learning more generally.
Comparison of tetrahydroaminoacridine and physostigmine on scopolamine-induced free swim behavior in the rat.
The effect of acetylcholinesterase inhibitors on free swim behavior in rats pretreated with scopolamine (0.32 mg/kg, IP) was examined. Long-Evans rats received a single 5-min testing trial in a 1.5 m black swimming pool, and swim distance in three concentric annulus corridors (peripheral, middle, and inner) and the number of body-turn transitions (greater than 45 degrees) were measured. Physostigmine (1.0 mg/kg, IP) increased swim distance in the middle and inner annulus corridors, compared to tetrahydroaminoacridine (2.0 mg/kg and 10 mg/kg, IP) and scopolamine alone (control) (Ps less than 0.01), and increased body-turn transitions, compared to all the other groups (Ps less than 0.05), but had no significant effect on peripheral annulus corridor swim distance, total swim distance, or swim speed. The results suggest that physostigmine produces uniquely different free swim patterns from tetrahydroaminoacridine following cholinergic blockade. These findings have implications for investigations attempting to restore spatial learning and navigation (e.g., Morris water maze) using acetylcholinesterase inhibitors following experimentally-induced cholinergic losses.
Childhood drowning and near-drowning in Brisbane: the contribution of domestic pools.
OBJECTIVE: To describe the epidemiology of domestic swimming pool drowning and near-drowning in Brisbane and to examine the efficacy of a broad range of preventive options, including pool fences. DESIGN: A prospective, hospital-based, injury surveillance system to describe the epidemiology of drowning and near-drowning and a community survey to describe pool fencing. SETTING: The surveillance questionnaire was completed at presentation in the Emergency Department by the parent, nurse and doctor. Personal interviews in households that were randomly selected by means of a stratified sampling scheme provided the pool fencing description. PARTICIPANTS: All 139 children suffering from an immersion injury resulting in presentation at a hospital in the catchment area of The Mater Children's Hospital were included. There were 204 households with a swimming pool in the 1024 households interviewed in the community survey. RESULTS: The 100 domestic pool drownings and near-drownings were equivalent to 15.5 incidents per year per 100,000 children aged 0-13 years and 64.9 per year per 100,000 for the critical 1-3 years age group. Of 72 children who gained unintended access to a domestic pool, 88.9% were less than 3 years of age and 52.8% were less than 2 years. All 10 of the children who drowned and five who were severely brain damaged (age range, 12-32 months) were in this group. The risk of a drowning or near-drowning involving unintended access to an unfenced pool is 3.76 times higher than the risk associated with a fenced pool (95% confidence limits for relative risk: 2.14, 6.62). CONCLUSIONS: Pool fences are an effective method of preventing child drownings and near-drownings. This effectiveness can be further improved if compliance with gate closure can be enhanced. This should be emphasised in health promotion accompanying the introduction of universal pool fencing.