Accumulation of potentially toxic elements in road deposited sediments in residential and light industrial neighborhoods of Singapore.

Road deposited sediments (RDS) are a valuable environmental medium for characterizing contaminant levels in urban areas; and their associated potentially toxic elements (PTEs) can directly impact both human and aquatic health. In this study, RDS were collected from 15 co-located industrial and residential roads throughout Singapore to determine the effect of land use on contaminant levels. A second pilot study was designed to quantify the efficiency of road sweeping in removing different RDS grain size fractions from industrial and residential roads. The fine fraction (<63 µm) of all RDSs was analyzed for over 40 elements. Eleven elements that reflect geogenic and anthropogenic sources were examined in detail (Al, Co, Cr, Cu, Fe, Ni, Pb, Sb, Sc, Si, and Zn). Industrial RDS had statistically higher concentrations of Co, Cr, Fe, and Ni than residential RDS. Potentially toxic elements Cu, Pb, Sb, and Zn were enriched >10-fold at all locations compared to upper continental crust values. Concentrations of Cu, Pb and Zn exceeded aquatic sediment probable effect concentration levels, suggesting they could generate a toxic response in bottom-dwelling aquatic organisms. Traffic was equally heavy at both industrial and residential sites, but large trucks and machinery comprised a larger proportion of the traffic in the industrial areas. Traffic was not significantly correlated with the PTE (i.e., Cu, Pb, Sb and Zn) concentrations. Plausible anthropogenic contaminant sources include vehicles (e.g., brake and tire wear, vehicle emissions) and several industrial activities including metal works, oil processing, and waste incineration. Street sweeping was effective in removal of large organic debris and inorganic RDS, but it was ineffective in removing the geochemically important fraction, i.e., <125 µm.

High-efficiency particulate air filter test stand and aerosol generator for particle loading studies.

This manuscript describes the design, characterization, and operational range of a test stand and high-output aerosol generator developed to evaluate the performance of 30 x 30 x 29 cm(3) nuclear grade high-efficiency particulate air (HEPA) filters under variable, highly controlled conditions. The test stand system is operable at volumetric flow rates ranging from 1.5 to 12 standard m(3)/min. Relative humidity levels are controllable from 5%-90% and the temperature of the aerosol stream is variable from ambient to 150 degrees C. Test aerosols are produced through spray drying source material solutions that are introduced into a heated stainless steel evaporation chamber through an air-atomizing nozzle. Regulation of the particle size distribution of the aerosol challenge is achieved by varying source solution concentrations and through the use of a postgeneration cyclone. The aerosol generation system is unique in that it facilitates the testing of standard HEPA filters at and beyond rated media velocities by consistently providing, into a nominal flow of 7 standard m(3)/min, high mass concentrations (approximately 25 mg/m(3)) of dry aerosol streams having count mean diameters centered near the most penetrating particle size for HEPA filters (120-160 nm). Aerosol streams that have been generated and characterized include those derived from various concentrations of KCl, NaCl, and sucrose solutions. Additionally, a water insoluble aerosol stream in which the solid component is predominantly iron (III) has been produced. Multiple ports are available on the test stand for making simultaneous aerosol measurements upstream and downstream of the test filter. Types of filter performance related studies that can be performed using this test stand system include filter lifetime studies, filtering efficiency testing, media velocity testing, evaluations under high mass loading and high humidity conditions, and determination of the downstream particle size distributions.

New genotypes and factors associated with Cryptosporidium detection in mussels (Mytilus spp.) along the California coast.

A 3 year study was conducted to evaluate mussels as bioindicators of faecal contamination in coastal ecosystems of California. Haemolymph samples from 4680 mussels (Mytilus spp.) were tested for Cryptosporidium genotypes using PCR amplification and DNA sequence analysis. Our hypotheses were that mussels collected from sites near livestock runoff or human sewage outflow would be more likely to contain the faecal pathogen Cryptosporidium than mussels collected distant to these sites, and that the prevalence would be greatest during the wet season when runoff into the nearshore marine environment was highest. To test these hypotheses, 156 batches of sentinel mussels were collected quarterly at nearshore marine sites considered at higher risk for exposure to livestock runoff, higher risk for exposure to human sewage, or lower risk for exposure to both faecal sources. Cryptosporidium genotypes detected in Haemolymph samples from individual mussels included Cryptosporidium parvum, Cryptosporidium felis, Cryptosporidium andersoni, and two novel Cryptosporidium spp. Factors significantly associated with detection of Cryptosporidium spp. in mussel batches were exposure to freshwater outflow and mussel collection within a week following a precipitation event. Detection of Cryptosporidium spp. was not associated with higher or lower risk status for exposure to livestock faeces or human sewage sources. This study showed that mussels can be used to monitor water quality in California and suggests that humans and animals ingesting faecal-contaminated water and shellfish may be exposed to both host-specific and anthropozoonotic Cryptosporidium genotypes of public health significance.

Two consecutive randomized controlled pertussis booster trials in children initially vaccinated in infancy with an acellular vaccine: The first with a five-component Tdap vaccine to 5-year olds and the second with five- or monocomponent Tdap vaccines at age 14-15 years.

Prior study children from a DTaP efficacy trial were recruited at ages 5 and 15 years to randomized booster trials addressing immunogenicity and reactogenicity; 475 preschool children received mixed or separate injections of a reduced antigen vaccine (Tdap5, Sanofi Pasteur MSD) and an inactivated polio vaccine, and 230 adolescents received the same or another booster vaccine (Tdap1, SSI, Denmark). Pre-vaccination antibody concentrations against pertussis antigens were significantly higher at 15 than 5 years of age, probably due to natural boosting between the studies. Tdap5 induced comparable anti-PT concentrations at both ages, but antibody responses were significantly higher to filamentous haemagglutinin, pertactin and fimbriae 2/3 in adolescents. As expected, a higher amount of PT (Tdap1, 20µg) induced a stronger anti-PT response than a lower amount (Tdap5, 2.5µg). The frequency of adverse events was low and there were no serious adverse reactions. All local reactions had an early onset and a short duration. A large swelling or redness of more than half of the upper arm circumference was reported in 8/475 5-year-olds and in 6/230 15-year-olds. Children vaccinated with Tdap5 reported more moderate pain in adolescence than at preschool age, whereas itching was only reported in preschool children. Sweden introduced DTaP vaccines in 1996 after a 17-year hiatus with no general pertussis vaccination and pertussis was still endemic at the time of the studies. The frequency of adverse events was nevertheless low in both preschool children and adolescents and antibody responses were adequate. These studies document immunogenicity and reactogenicity in a trial cohort consecutively vaccinated with acellular pertussis vaccines from infancy to adolescence. The adolescent study was registered at ClinicalTrials.gov on 26 March 2009 (NCT00870350).

Primary immunization of infants with an acellular pertussis vaccine in a double-blind randomized clinical trial.

The rate of adverse reactions and the immunogenicity of a two-component acellular pertussis vaccine as compared with a plain whole-cell vaccine and a placebo were evaluated for primary immunization in 319 6-month-old infants in a double-blind randomized clinical trial. The acellular vaccine produced few and mild systemic and local reactions. Fever (greater than or equal to 38 degrees C) occurred in 6% to 8% of acellular vaccinees as opposed to 25% to 37% of whole-cell vaccinees. Redness (greater than or equal to 1 cm) appeared in 2% to 13% of the acellular vaccine and 24% to 32% of the whole-cell vaccine recipients. Antibody response to pertussis toxin measured in a neutralization test was obtained in 97% to 100% of the infants receiving either two or three doses of the acellular vaccine as compared to 59% after three doses of whole-cell vaccine.

An international perspective on child day-care health.

If we are committed to the health and development of children, we need to recognize that the vast majority of the world's women are working women. In Africa, 80% of the women are actively engaged in economic activities outside the home. The "economic miracle" in Southeast Asia was made possible by the nimble fingers of thousands of women working in textile and electronics factories. There is need for pre-day-care advocacy for infants, through promotion of breast feeding and maternity leave. When the mother returns to work, the standard of the International Labor Organization should be applied, namely" ...the care of children while the parents are working cannot be ignored because it forms a focal point on which three main concerns of development policy--work, health, and education--converge." Several principles emerged from the presentations in the international panel: 1. Child-care programs must be community based, using the resources of the families and the community organizations themselves. 2. Programs require the active involvement of the communities, women's groups, and other partners. 3. Programs are modified by innovations created by community organizations, universities, and other groups. 4. Programs require the mobilization of trained young men and women into the field of early childhood education and development. This international panel provided an overall uniting theme, that throughout the world the hope for the survival and better life for children unites parents of every country and every creed. This is one of the most powerful and strongest motivational resources in the world.(ABSTRACT TRUNCATED AT 250 WORDS)

Mortality and morbidity from invasive bacterial infections during a clinical trial of acellular pertussis vaccines in Sweden.

A double blind placebo-controlled efficacy trial of two acellular pertussis vaccines was conducted in 3801 6- to 11-month-old children. Four vaccinated children died during 7 to 9 months follow-up as a result of Haemophilus influenzae type b meningitis, heroin intoxication with concomitant pneumonia, suspected septicemia, and Neisseria meningitidis Group B septicemia. From the actual death rate in children belonging to the same birth cohort in Sweden that could have been eligible for the trial, one death was expected among vaccinated children. Several investigations were carried out to examine the possibility that the deaths could be causally related to the vaccination. The relative risk for hospitalization due to systemic or respiratory infections was 1.07 (95% confidence interval, 0.95 to 1.20) and 0.83 (95% confidence interval, 0.64 to 1.08) in the vaccine groups as compared with the placebo group. Subsets of the population were studied for signs of immunosuppression. There was no indication of immunoglobulin deficiency or any sign of clinically significant leukopenia or lymphocytosis in vaccine recipients. The results of this analysis provide no evidence for a causal relation between vaccination with the studied acellular pertussis vaccines and altered resistance to invasive disease caused by encapsulated bacteria. The hypothesis that the two variables are related, however, cannot be refuted from these data.

Defining surrogate serologic tests with respect to predicting protective vaccine efficacy: pertussis vaccination.

The first efficacy trial of pertussis vaccines with defined purified antigens failed to demonstrate a serologic correlate of protection, although both tested vaccines were shown to give significant protection against typical whooping cough. The antibody response to pertussis toxoid was dose dependent. A lower anti-PT response in the two-component vaccine, containing one-half the amount of PT in the one-component vaccine, seemed to be compensated by a significant anti-FHA response, since both vaccines conferred similar protection against typical illness. However, the immunologic mechanisms whereby protection is conferred remain unclear. At present antibody responses to the antigens included in the first tested vaccines could be used as pseudoindicators of protection. The group of vaccinated infants who were protected did differ in their antibody profile as compared to unvaccinated infants. Tentatively, candidate vaccines should elicit no less antibody responses to PT and FHA as those elicited by the above one- and two-component vaccines, respectively. The response to other antigens such as pertactin and fimbriae cannot be related to protection at present. Ongoing efficacy trials of a number of pertussis vaccines of varying composition may or may not provide immunological correlates of protection against pertussis. The trials ought to be subjected to a preplanned, independent (meta)analysis with defined end points to increase the understanding of the contribution of various antigens to the protective efficacy of pertussis vaccines.

Acellular pertussis vaccines--a question of efficacy.

Whole cell pertussis vaccine is considered to offer at least 80% protection against typical whooping cough. The quest for an equally effective but less reactogenic vaccine is now drawing to a close. During the forthcoming year a number of efficacy trials of acellular pertussis vaccines will be terminated. A variety of vaccines containing one, two, three or five purified pertussis antigens are being tested in Germany, Italy, Senegal and Sweden. About 30,000 infants have been enrolled in placebo-controlled studies and more than 100,000 in whole cell vaccine-controlled trials. The final plans for analysis of a Swedish placebo-controlled trial of whole cell and acellular vaccines is presented. Due to the unexpected high incidence of pertussis in Sweden during 1993-1994, relative risk comparisons between vaccines will be attempted in that trial, in addition to estimating absolute efficacy. A crucial issue is to what extent data may be compared between trials, given differences in design, vaccination schedules, and chosen endpoints. A primary case definition of laboratory-confirmed pertussis with at least 21 days of paroxysmal cough have been adopted in most trials. Pre-planned meta-analysis using this single endpoint will facilitate comparisons between vaccines. Serological correlates to protection in individuals will be sought in the ongoing placebo-controlled trials. The concept of a serological correlate valid for a vaccinated population but not necessarily for the vaccinated individual, as is the case with Hib vaccines, may turn out to be the only alternative to performing large efficacy trials in the future.

Technical note: fluoride pre-treatment effects on microleakage of a resin bonding agent.

This pilot study reports the effect of fluoride pre-treatment of dentin and enamel on microleakage of a resin bonding agent. Pairs of circular class V cavities involving 50% enamel and 50% cementum were cut in 12 extracted third molars. Each tooth contained a control and a treatment cavity (matched-pair design). A stannous fluoride solution (0.717% SnF2, Gel-Kam, Scherer Laboratories, Dallas, TX) was applied to the entire treatment preparation of each tooth. A dentin resin bonding system (Scotchbond 2 with Scotchprep, a dentin primer, 3M Dental Products Div., St. Paul, MN) was applied per manufacturer's instructions. Silux resin (3M) was placed over the resin bonding agent, light-cured, and finished. The teeth were subjected to 500 temperature cycles between 5 and 55 degrees C. A silver nitrate staining technique was used for evaluation of microleakage. The mean leakage for the control was 2235 +/- 1146 microns, and 2105 +/- 1052 microns for the fluoride treatment sites. It is concluded, from this pilot study with small sample size, that pre-treatment with fluoride of dentin and enamel prior to the placement of a resin bonding agent produced no significant change in microleakage (Student's t test for paired samples, p = 0.6492).

Bond strength of a light-cured and two auto-cured glass ionomer liners.

Ninety-nine extracted human molar teeth were used in this study comparing the shear bond strengths on dentine of one light-cured and two auto-cured polyalkenoate (glass ionomer) cements. Bond strength can be influenced by differences in tooth structure. A balanced-incomplete block design (Hull and Nie, 1981) was used to reduce variation attributable to such differences. Cements were applied to paired dentine surfaces in combinations such that 66 tooth sides were treated with each material. A light-cured dentinal adhesive and composite resin restorative material were then placed and shear bond strength testing was conducted exactly 24 h after the completion of each specimen. Mean forces (MPa) for the three materials were compared using an appropriate analysis of variance model (balanced-incomplete-blocks) The shear bond strengths (MPa) of the light-cured liner (Espe, Seefeld/Oberbay, FRG) was 4.71 +/- 1.16. Vitrabond showed the greatest variance of all three materials tested, however this material's average bond strength was greater than the maximum achieved for the other materials. Student-Newman-Keuls comparison of means showed that all cements differed significantly from each other (alpha = 0.05). It is concluded that the light-cured glass ionomer liner exhibited significantly better shear bond strength performance than the two auto-cured glass ionomers tested.

Bond strength of six dentinal adhesives.

This study compared the shear bond strengths on dentine of five dentine adhesives against Scotchbond 2 as a control. Dentine specimens from 225 extracted human permanent molar teeth were used in a matched-pair design, such that 45 tooth sides were treated along with the matching control for each of the five test materials. Shear bond strength testing was conducted 24 h after the completion of each specimen. Results showed that mean force (MPa) for the materials were: XR Bond, 17.1 +/- 5.1; Scotchbond Multi-Purpose, 15.9 +/- 6.5; Syntac, 13.5 +/- 8.6; All-Bond 2, 6.2 +/- 4.1; Scotchbond 2 (control composite score), 4.9 +/- 3.0; Denthesive, 3.4 +/- 1.7. Matched pair t-test comparisons with Scotchbond 2 control were: XR Bond, P = 0.0005; Scotchbond Multi-Purpose, P = 0.0005; Syntac, P = 0.0005; All-Bond 2, P = 0.0368; Denthesive, P = 0.005. Analysis of variance determined a statistically significant difference (P = 0.05) between the means of the bond strengths, which fell into four groups: Group A, XR Bond and Scotchbond Multi-Purpose; Group B, Syntac; Group C, All-Bond 2 and Scotchbond 2; Group D, Scotchbond 2 and Denthesive. In Group C, there was no significant difference between Scotchbond 2 and All-Bond 2. In Group D there was no significant difference between Scotchbond 2 and Denthesive, however, there was significant difference between All-Bond 2 and Denthesive. It was concluded that XR Bond and Scotchbond Multi-Purpose had significantly better shear bond strength than the other dentine adhesives.

Marked decline in pertussis followed reintroduction of pertussis vaccination in Sweden.

Immunisation against pertussis with an acellular pertussis vaccine for children at 3, 5, and 12 months was included in the Swedish vaccination programme in January 1996, 17 years after the withdrawal of whole cell vaccine in 1979. Within months coverage r

Clinical evaluation of resin-bonded bridges: a retrospective study.

Eighty-five patients with a total of 103 resin-bonded bridges placed by practitioners at the University of Minnesota School of Dentistry between 1982 and 1989 were recalled for a clinical evaluation of their restorations. Tissue condition, patient satisfaction, bridge failures by location and by sex of patient, and average length of service for both successful and failed bridges were recorded. After an average service of 3.25 years, 12.6% of the fixed partial dentures had debonded. Debondings occurred most frequently in the mandibular arch. Failures occurred more frequently in men than in women, and prostheses with more than two retainers had twice the probability for problems.

Retentive strength of six temporary dental cements.

The retentive strength of three zinc oxide-eugenol cements and three noneugenol-containing zinc oxide cements and the effect of the addition of petrolatum on retention were tested. The addition of petrolatum was found to affect retention of the cements significantly. Retention strengths varied from 1.6 kg to 40.0 kg. Of the Class 1, Type 2, systems tested, noneugenol cements had higher retentive values than did the eugenol-containing cements.

Invasive bacterial infections during an efficacy trial of acellular pertussis vaccines--implications for future surveillance in pertussis vaccine programmes.

During a placebo controlled trial of acellular pertussis vaccines a cluster of invasive bacterial infections with fatal outcome occurred among vaccinated children as compared with unvaccinated Swedish children of the same birth cohort (4). Clinical and immunological studies did not support the hypothesis of an immunosuppressive effect of the vaccines, which would explain the deaths, but the hypothesis could not be refuted by the data. To evaluate the safety of acellular pertussis vaccines regarding rare severe events--in particular invasive infectious diseases--prospective studies seem to be needed, comparing very large groups. A coordinated and controlled vaccine programme during 1-2 years in most of Sweden combined with national reports of invasive infections may serve as a basis for such a study. A possible study design is given below.

[Vaccine protection of Swedish children. Time for revision of replacing doses of diphtheria, tetanus, polio and pertussis]. / Svenska barns vaccinskydd. Dags att se över påfyllnadsdoserna för difteri, stelkramp, polio och kikhosta.

The Swedish vaccination programme against diphtheria, tetanus, pertussis, polio and Haemophilus influenzae type b is characterized by few, widely spaced doses. Swedish schoolchildren have low diphtheria antibody levels compared to children in other countries. The introduction of acellular pertussis vaccine in 1996 has markedly cut the pertussis incidence in all ages except school-age children. There are now reasons to consider replacing the present fourth dose of inactivated polio vaccine given at 5 years of age and the diphtheria-tetanus toxoids given at 10 years of age with a combined diphtheria-tetanus-polio-acellular pertussis vaccine dose to be given at 5-6 years of age. A fifth dose of a DTPaPolio vaccine should be considered at 15-18 years of age.