Household interventions for prevention of domestic lead exposure in children

BACKGROUND

Lead poisoning is associated with physical, cognitive and neurobehavioral impairment in children and many household interventions to prevent lead exposure have been trialled.

OBJECTIVES

To determine the effectiveness of household interventions in preventing or reducing lead exposure in children as measured by reductions in blood lead levels and/or improvements in cognitive development.

SEARCH STRATEGY

Trials were identified through electronic searches of CENTRAL 2006 (Issue 1), MEDLINE 1966 to March 2006, and thirteen other electronic databases and contacting experts to find unpublished studies.

SELECTION CRITERIA

Randomised and quasi randomised trials of household educational or environmental interventions to prevent lead exposure in children where at least one standardised outcome measure was reported.

DATA COLLECTION AND ANALYSIS

Two reviewers independently reviewed all eligible studies for inclusion, assessed study quality and extracted data. Triallists were contacted to obtain missing information.

MAIN RESULTS

Twelve studies (2239 children) were included. All studies reported blood lead level outcomes and none reported on cognitive or neurobehavioural outcomes. Studies were subgrouped according to their intervention type. Meta-analysis of both continuous and dichotomous data was performed for subgroups where appropriate. Educational interventions were not effective in reducing blood lead levels (continuous: WMD 0.13, 95% CI -0.30, 0.56, I2 = 41.6; dichotomous >/= 10 microg/dL (>/= 0.48 micromol/l): RR 1.02 (95% CI 0.79, 1.30, I2 = 0); dichotomous >/= 15 microg/dL (>/=0.72 micromol/l): RR 0.60, 95% CI 0.33, 1.09, I2 = 0). Meta-analysis of the dichotomous data for the dust control subgroup found no evidence of effectiveness. The studies using soil abatement (removal and replacement) and combination intervention groups were not able to be meta-analysed due to substantial differences between studies.

AUTHORS' CONCLUSIONS

Currently there is no evidence of effectiveness for household interventions for education or dust control measures in reducing blood lead levels in children as a population health measure. There is insufficient evidence for soil abatement or combination interventions. Further trials are required to establish the most effective intervention for prevention of lead exposure. Key elements should include longer term follow up and measures of compliance as well as performing trials in developing countries and differing socio-economic groups in developed countries.

Control of Lunar and Martian dust--experimental insights from artificial and natural cyanobacterial and algal crusts in the desert of Inner Mongolia, China

Studies on the colonization of environmentally extreme ground surfaces were conducted in a Mars-like desert area of Inner Mongolia, People's Republic of China, with microalgae and cyanobacteria. We collected and mass-cultured cyanobacterial strains from these regions and investigated their ability to form desert crusts artificially. These crusts had the capacity to resist sand wind erosion after just 15 days of growth. Similar to the surface of some Chinese deserts, the surface of Mars is characterized by a layer of fine dust, which will challenge future human exploration activities, particularly in confined spaces that will include greenhouses and habitats. We discuss the use of such crusts for the local control of desert sands in enclosed spaces on Mars. These experiments suggest innovative new directions in the applied use of microbe-mineral interactions to advance the human exploration and settlement of space.

Cleaning efficacy of high-efficiency particulate air-filtered vacuuming and "dry steam" cleaning on carpet

Previous studies for lead exposure reduction have indicated the difficulty in reducing surface contamination of carpets with the use of regular vacuum cleaners. To find a solution, a household vacuum cleaner equipped with a high-efficiency particulate air (HEPA) filter and a dust finder indicator, and a "dry steam" cleaner previously reported effective in reducing dust mite allergens in carpets and mattresses were tested for effectiveness in reducing lead dust in carpets. Fifty homes of lead-exposed children were tested in New Jersey. A selected carpet in the living area of each home was tested with two interventions: half was cleaned by HEPA vacuuming twice (VAC-VAC) and the other half by dry steaming between the two HEPA vacuumings (VAC-DSC-VAC). Wipe and vacuum samples, representing surface dust and total dust collections, respectively, were taken before and after cleaning. The wipe and vacuum sample data indicated that both cleaning methods substantially reduced dust lead levels (p < 0.001). The mean percent reductions in lead loading were approximately 29% and 40% for the VAC-VAC and VAC-DSC-VAC interventions, respectively. The difference between the two postcleaning levels was statistically significant by wipe sampling (p = 0.038) but was marginally insignificant by vacuum sampling (p = 0.072). A subset of sample data collected before repeat vacuuming (VAC-DSC) suggested that repeat vacuuming after dry steam cleaning is unnecessary. In summary, slow and steady HEPA vacuuming with the help of a dust finder indicator reduces surface and overall lead dust in carpets, and dry steam cleaning further reduces surface lead contamination as compared with HEPA vacuuming alone.

A systematic review and meta-analysis of interventions used to reduce exposure to house dust and their effect on the development and severity of asthma

OBJECTIVES

We assessed whether any household dust reduction intervention has the effect of increasing or decreasing the development or severity of atopic disease.

DATA SOURCES

Electronic searches on household intervention and atopic disease were conducted in January 2007 in EMBASE, MEDLINE, and the Cochrane Central Register of Controlled Trials. No date or language restriction was placed on the literature search.

DATA EXTRACTION

We included randomized controlled trials comparing asthma outcomes in a household intervention group with either placebo intervention or no intervention.

DATA SYNTHESIS

Fourteen studies met the inclusion criteria. Eight recruited antenatally and measured development of atopic disease. Six recruited known atopic individuals and measured disease status change. Meta-analyses on the prevention studies found that the interventions made no difference to the onset of wheeze but made a significant reduction in physician-diagnosed asthma. Meta-analysis of lung function outcomes indicated no improvement due to the interventions but found a reduction in symptom days. Qualitatively, health care was used less in those receiving interventions. However, in one study that compared intervention, placebo, and control arms, the reduction in heath care use was similar in the placebo and intervention arms.

CONCLUSIONS

This review suggests that there is not sufficient evidence to suggest implementing hygiene measures in an attempt to improve outcomes in existing atopic disease, but interventions from birth in those at high risk of atopy are useful in preventing diagnosed asthma but not parental-reported wheeze.

Efficiency of a tool-mounted local exhaust ventilation system for controlling dust exposure during metal grinding operations

In general, control of metal dust from hand-held disk grinders is difficult because such respirable dust tends to disperse in every direction around the grinding wheel and cannot be captured effectively by a conventional exhaust hood. The author described the application of a custom-made tool-mounted local exhaust ventilation (LEV) system attached to a hand-held disk grinder, and by laboratory experiments assessed its effectiveness at dust control. The effectiveness of the LEV for dust control was assessed by determining the respirable dust concentration around the grinding wheel during metal surface grinding with and without the use of the LEV. It was shown that the average respirable grinding dust concentration decreased from 7.73 mg/m(3) with the LEV off to 4.87 mg/m(3) with the LEV on, a mean dust generation reduction of about 37%.

The Effectiveness of Various Biofiltration Substrates in Removing Bacteria, Endotoxins, and Dust from Ventilation System Exhaust from a Chicken Hatchery

The objective of this study was to evaluate the effectiveness of various organic and organic-mineral biofilter media in purifying ventilation exhaust from a chicken hatchery room. Three different substrates were tested. Efficiency levels for the removal of dust, gram-negative bacteria, and bacterial endotoxin were recorded. The microbiological properties of the substrates were also studied. All of the biofilter substrates were highly effective in removing gram-negative bacteria, moderately effective in reducing dust levels, and only slightly effective in removing endotoxin. The substrate that was most efficient in retaining bioaerosols was the organic-mineral medium containing 20% halloysite, 40% compost, and 40% peat, which generally had at least satisfactory efficiency values for removing all of the contaminants tested.

Respirable dust concentrations in equine stables. Part 2: The benefits of soaking hay and optimising the environment in a neighbouring stable

The effect of soaking hay to minimise equine breathing zone respirable dust concentration (RDC) is unknown, as is the duration of soaking required. Additionally, the influence of the bedding and forage used in one stable on the mean and maximum RDC in a neighbouring stable within a common airspace is unknown. Consequently, in the management of equine environmental respiratory disease uncertainty remains about the necessity for optimising conditions in neighbouring stables. Investigations using a real-time continuous particle monitor revealed that when feeding hay, horses' mean breathing zone RDC was significantly reduced if the hay was immersed or soaked for a prolonged time, prior to feeding. There was no advantage in soaking for an extended time period. Implementing management changes in one stable (changing from straw bedding and hay feeding to wood shavings bedding and haylage feeding) significantly reduced mean and maximum background RDC in a neighbouring stable within a common airspace.

Modelling Exposure in Flour Processing Sectors in The Netherlands: a Baseline Measurement in the Context of an Intervention Program

INTRODUCTION

Recent studies have shown that even low exposure levels to flour dust and related allergens can cause severe respiratory symptoms. In The Netherlands the Dutch government and responsible branch organizations [from bakeries (traditional & industrial), flour mills and bakery ingredient producers] signed a covenant to reduce exposure to flour dust and decrease the prevalence of work-related occupational airway disease. This paper describes a sector wide survey to measure exposure to flour dust, wheat allergens and fungal alpha-amylase. The results are being used to underpin various elements of the covenant.

METHODS

A dataset containing 910 personal measurements was compiled from four field studies containing information on exposure and potential determinants. The dataset represents a baseline estimate of exposure for four major flour processing sectors in The Netherlands. Exposure models for all sectors and agents were generated, based on job, tasks and company size, taking into account worker and company as random effect components. Use of control measures and, where possible, their effect were evaluated.

RESULTS

Flour dust and enzyme exposures vary strongly between sectors. The job performed and specific tasks were identified as important determinants of exposure. The number of identified control measures during walk-through surveys, and their effectiveness in reduction of dust exposure was generally limited. The exposure models explained significant exposure variability between companies and workers but performed poorly in explaining day to day differences in exposure.

DISCUSSION

The dataset serves as a baseline estimate and will be compared with a post intervention survey in the near future. The information obtained on control measures can be used to optimize the intervention scenarios that will be implemented in the different sectors by external occupational hygienists. The predictive exposure models will provide a relevant measure of average personal exposure that will be used in the sector wide health surveillance system.

Occupational exposure to wood dust in the british woodworking industry in 1999/2000

Exposure to inhalable wood dust and compliance with the British Control of Substances Hazardous to Health (COSHH) Regulations 1999 were assessed at a representative cross-section of the British woodworking industry. Median exposures ranged from 1.5 to 2.8 mg/m(3) across the selected industry groups, the lowest being in sawmilling and planing of wood. Overall, 27% of values exceeded the maximum exposure limit (MEL) at that time of 5 mg/m(3). These results showed that the percentage of exposures above the MEL was less than in a survey carried out 10 years earlier. A wide variation of exposures was identified at different machines and tasks. At least 90% at bandsawing and cross-cut sawing were <5 mg/m(3). In contrast, dust emission at circular sawing, sanding, cleaning and a miscellaneous group of activities was poorly controlled. Between 32 and 50% of results from these categories exceeded 5 mg/m(3). The lower exposures in sawmills were largely attributable to the low usage of sanders and a group of circular saws, to the high use of bandsaws and moulders and to coarser dust from undried timber. Compliance with the COSHH Regulations was inadequate. Companies that claimed to have some form of written COSHH assessment were generally no more effective at controlling exposure to dust than those without an assessment. Similarly the ability of premises that provided information, instruction and training on the risks to health from wood dust and on measures to prevent or control those risks was not generally greater than in those that did not. Maintenance of local exhaust ventilation systems emerged as essential for achieving good control. Companies that followed both the statutory 14-monthly thorough examination and testing schedule and a weekly check system were more successful in this respect than those that did not. In spite of this, local exhaust ventilation alone provided insufficient dust control at several woodworking activities.

[Physico-chemical characteristics of ambient particles settling upon leaf surface of six conifers in Beijing]

The study on the density of ambient particles settling upon the leaf surface of six conifers in Beijing, the micro-configurations of the leaf surface, and the mineral and element compositions of the particles showed that at the same sites and for the same tree species, the density of the particles settling upon leaf surface increased with increasing ambient pollution, but for various tree species, it differed significantly, with the sequence of Sabina chinensis and Platycladus orientalis > Cedrus deodara and Pinus bungeana > P. tabulaeformis and Picea koraiensis. Due to the effects of road dust, low height leaf had a larger density of particles. The density of the particles was smaller in summer than in winter because of the rainfall and new leaf growth. The larger the roughness of leaf surface, the larger density of the particles was. In the particles, the overall content of SiO2, CaCO3, CaMg(CO3,), NaCl, 2CaSO4 . H2O, CaSO4 . 2H2O and Fe2O3 was about 10%-30%, and the main minerals were montmorillonite, illite, kaolinite and feldspar. The total content of 21 test elements in the particles reached 16%-37%, among which, Ca, Al, Fe, Mg, K, Na and S occupied 97% or more, while the others were very few and less affected by sampling sites and tree species.

Dust explosions-cases, causes, consequences, and control

Dust explosions pose the most serious and widespread of explosion hazards in the process industry alongside vapour cloud explosions (VCE) and boiling liquid expanding vapour explosions (BLEVE). Dust explosions almost always lead to serious financial losses in terms of damage to facilities and down time. They also often cause serious injuries to personnel, and fatalities. We present the gist of the dust explosion state-of-the-art. Illustrative case studies and past accident analyses reflect the high frequency, geographic spread, and damage potential of dust explosions across the world. The sources and triggers of dust explosions, and the measures with which different factors associated with dust explosions can be quantified are reviewed alongside dust explosion mechanism. The rest of the review is focused on the ways available to prevent dust explosion, and on cushioning the impact of a dust explosion by venting when the accident does take place.

House dust mite avoidance measures for perennial allergic rhinitis

BACKGROUND

In developed countries, it is estimated that approximately 30% of the general population suffer from one or more allergic disorders, of which allergic rhinitis is the most common. Perennial rhinitis is most often due to allergy to the house dust mite. In such patients, house dust mite avoidance is logical, but there is considerable uncertainty regarding the efficacy and effectiveness of interventions designed to reduce dust mite exposure.

OBJECTIVES

To assess the benefit (and harm) of measures designed to reduce house dust mite exposure in the management of house dust mite sensitive allergic rhinitis.

SEARCH STRATEGY

Our search included the Cochrane Ear, Nose and Throat Disorders Group Trials Register, the Cochrane Central Register of Controlled Trials Register (CENTRAL) (The Cochrane Library, Issue 2, 2005), MEDLINE (1951 to 2005) and EMBASE (1974 to 2005). No restrictions on the language of publication were employed. The bibliography of each paper and other published reviews were checked for further references. The date of the last search was May 2005.

SELECTION CRITERIA

Randomised controlled trials (with or without blinding), in which house dust mite control measures have been evaluated in comparison with placebo or other dust mite avoidance measures, in patients with clinician diagnosed allergic rhinitis and confirmed allergy to dust mite.

DATA COLLECTION AND ANALYSIS

Two authors independently checked titles and abstracts identified by the searches and full text copies of all papers of potential relevance were considered. Trials were graded for methodological quality using the Cochrane approach. Data extraction was performed in a standardised manner. Meta-analysis was neither possible nor appropriate, because of the heterogeneity of the patient groups studied; a narrative overview of the results is therefore presented.

MAIN RESULTS

Seven trials satisfied the inclusion criteria. Of these, only two studies investigating the effectiveness of mite impermeable bedding covers were of good quality; the remaining five studies were small and of poor quality. Two trials investigated the efficacy of acaricides, another two trials investigated the role of high-efficiency particulate air filters; the remaining three trials investigated the efficacy of bedroom environmental control programmes involving use of house dust mite impermeable bedding covers. Six of the seven trials showed that the interventions result in significant reductions in house dust mite load when compared with control. Of the house dust mite interventions studied to date, acaricides appear to be the most promising type of intervention, although the findings from the two studies which employed these interventions need to be interpreted with care because of their methodological limitations. Use of house dust mite impermeable bedding as an isolated intervention is unlikely to offer clinical benefit. No serious adverse effects were reported from any of the interventions.

AUTHORS' CONCLUSIONS

Trials to date have on the whole been small and of poor methodological quality, making it difficult to offer any definitive recommendations on the role, if any, of house dust mite avoidance measures in the management of house dust mite sensitive perennial allergic rhinitis. The results of these studies suggest that use of acaricides and extensive bedroom based environmental control programmes may be of some benefit in reducing rhinitis symptoms and, if considered appropriate, these should be the interventions of choice. Isolated use of house dust mite impermeable bedding is unlikely to prove effective.

PCDD/DF concentrations at the inlets and outlets of wet scrubbers in Korean waste incinerators

To further understand the effects of wet scrubbers on PCDD/DF levels, it was measured the concentrations of PCDD/DF, dust, and other gaseous pollutants at both the inlets and the outlets of seven wet scrubbers. As a result, the concentrations of PCDD/DF at the inlets and outlets of the wet scrubbers ranged from 0.2 to 37.4, and 0.8 to 6.0 ng TEQ N m-3, respectively. With the exceptions of wet scrubbers F and G, the PCDD/DF levels decreased by and large in most wet scrubbers. It was thought that their relatively high removal efficiencies were more increased with heavier loads of dust and particle-bound PCDD/DF. On the other hand, it was also surveyed the increase of gaseous PCDD/DF in wet scrubber, where the total level of PCDD/DF was decreased. However, it was not sure whether it had been resulted from the thermal adsorption/desorption phenomenon between packing materials and emission gases or not. At the very least, however, although there still remains an unexplained aspect for the increase of gaseous PCDD/DF, it is clear that wet scrubbers can be sufficiently applied to remove PCDD/DF to a certain extent, if only removal efficiencies for the particle loads are high, and if a significant part of the PCDD/DF at the inlets is particle associated.

Screening Events to Reduce Farmers' Hazardous Exposures

Dairy farmers may be exposed to high levels of noise and dust. Protections against these hazards exist, but many farmers do not use them. An intervention consisting of hearing and respiratory screenings combined with personalized education was implemented. This study evaluates the impact of this intervention on farmers' self-reported use of personal protective equipment (PPE) and implementation of noise and dust abatement. Participants were screened as to noise (n=209) or dust (n=392) hazards and use of PPE. Following this, they were counseled on PPE use, and identification and reduction of noise or dust hazards. Counselors sought a pledge from the farmers to eliminate hazards and increase PPE use. Farmers were subsequently surveyed and asked whether they had implemented the changes. At baseline, 70% (146/209) of farmers exposed to high levels of noise reported poor use ("sometimes", "rarely", or "never") of hearing protection. Results indicated that two months after intervention, 25.2% (28/111) of these subjects had successfully improved their PPE use. At baseline, 79% (311/392) offarmers reported poor use of respiratory protection, with 27.3% (41/150) showing improvement in PPE use within the same time. Strategies to reduce noise hazards were identified by 92.8% (194/209) of hearing screening attendees; 13.2% (18/136) successfully reduced or removed exposure. These values for dust screening attendees were 98.2% (385/392) and 30.7% (54/176), respectively. Use of this intervention appears to be an effective method for increasing PPE use on the farm. However, it is not effective for reducing noise hazards.

Dust mite allergen avoidance as a preventive and therapeutic strategy

Asthma is a global health problem with genetic and environmental components. Indoor allergens have a major impact on asthma, and exposure in sensitized subjects can compromise lung function. A reduction in allergen exposure would seem a logical facet to treatment. Methods for reducing mite allergen levels that are effective in the laboratory may not work in the home and may not result in a clinical benefit. Six ongoing studies are investigating the effects of environmental control on the primary prevention of asthma and allergies. Although the Isle of Wight and Canadian studies provide encouraging results at age 8 and 7 years, respectively, it will be some time before a definitive public health message emerges. For secondary prevention, there is little evidence to support the use of mite-proof encasings as a single intervention in adults. In children, however, single or multifaceted interventions appear to be of some benefit.

Performance estimation of a Venturi scrubber using a computational model for capturing dust particles with liquid spray

A Venturi scrubber has dispersed three-phase flow of gas, dust, and liquid. Atomization of a liquid jet and interaction between the phases has a large effect on the performance of Venturi scrubbers. In this study, a computational model for the interactive three-phase flow in a Venturi scrubber has been developed to estimate pressure drop and collection efficiency. The Eulerian-Lagrangian method is used to solve the model numerically. Gas flow is solved using the Eulerian approach by using the Navier-Stokes equations, and the motion of dust and liquid droplets, described by the Basset-Boussinesq-Oseen (B-B-O) equation, is solved using the Lagrangian approach. This model includes interaction between gas and droplets, atomization of a liquid jet, droplet deformation, breakup and collision of droplets, and capture of dust by droplets. A circular Pease-Anthony Venturi scrubber was simulated numerically with this new model. The numerical results were compared with earlier experimental data for pressure drop and collection efficiency, and gave good agreements.

Exposure to Wood Dust Among Carpenters in the Construction Industry in The Netherlands

Exposure to wood dust was measured among 26 carpenters at 13 building projects. Sampling days were chosen randomly. Individual tasks, based on technology applied and material used during a working day, were sampled separately. From these task-based measurements, 8 h time-weighted average concentrations were calculated. Sampling was performed in accordance with a protocol that was developed by the carpentry and furniture industry and which was especially designed for sampling of wood dust. Eight hours time-weighted average exposure to wood dust ranged from 0.8 to 11.6 mg m(-3) with a geometric mean (GM) of 3.3 mg m(-3) and a geometric standard deviation (GSD) of 2.1. The probability of exceedance of the OEL, when comparing the estimated concentrations against the Dutch OEL of 2 mg m(-3), was 75%. The highest exposures were measured during sawing of Cempanel sheets. Task-based measurements showed lowest exposures when working outdoors (n = 11, AM = 2.2 mg m(-3)), but even then 5 out of 11 task-based exposures exceeded 2 mg m(-3). Indoors the exposure was 5.2 mg m(-3) (AM, n = 29) and when working both indoors and outdoors exposure was 16.2 mg m(-3) (AM, n = 4). In conclusion, long-term average exposure to wood dust among carpenters at construction sites is more than 1.5 times the present occupational exposure limit of 2 mg m(-3). The estimated probability of exceedance of the OEL was 75% and a reduction of exposure with a factor 5 is needed to bring the probability of exceedance below 5%. It is intended to lower the exposure limit to 1 mg m(-3) by 1 January 2007. In that case the probability of exceedance of the OEL is 95% and a reduction of exposure with a factor 10 is needed to bring the probability of exceedance below 5%. This can be achieved by using alternative materials, preparation of building material in workshops equipped with exposure controls, alternative equipment and improved ventilation and good housekeeping.