Environmental risk assessment of zinc in European freshwaters: A critical appraisal

A risk assessment report (RAR) on zinc and zinc compounds has recently been prepared in the framework of the European Union (EU) Council Regulation 793/93/EEC on Existing Chemicals. The EU Scientific Committee on Human and Environmental Risks (SCHER) has, however, expressed some fundamental, science-based concerns about the approach followed and the conclusions. The main objective of the present study was to assess the potential environmental risks associated with current use patterns of Zn in nine EU river basins in Germany, France and Belgium, thereby using more advanced methodologies which are largely in line with the recommendations made by SCHER. This included (i) avoiding working with measured Zn concentrations from monitoring stations that were potentially influenced by point sources and/or historical contamination, (ii) the full bioavailability normalization of all chronic ecotoxicity data to river basin specific physico-chemistry using biotic ligand models (BLM), prior to deriving predicted no effect concentrations (PNEC) with the species sensitivity distribution (SSD) approach, and (iii) the use of a probabilistic framework for risk characterization. Further, a total risk approach instead of an added risk approach was used, and the PNEC was equated to the HC5-50 without an additional assessment factor. Based on monitoring data we estimated predicted environmental concentrations (PEC) for the different EU river basins between 1.3 and 14.6 µg dissolved Zn/L. PNEC values varied between 22.1 and 46.1 µg dissolved Zn/L. This resulted in deterministic risk characterization ratios (RCR) that were below 1 in all river basins, suggesting that there is no deterministic regional risk associated with current use patterns of Zn in these river basins. With the probabilistic approach we identified rather limited risks, i.e., between < 0.4 and 18.3%. When the EU RAR approach was applied to the same monitoring datasets, deterministic risks were found in different river basins. A detailed analysis showed that this different deterministic conclusion of risk is mainly due to the fact that the EU RAR (i) uses an additional assessment factor of 2 to derive the PNEC and (ii) uses a more conservative approach for implementing bioavailability (BioF approach). We argue that the larger conservatism in the EU RAR mainly originates from decisions made to deal in a pragmatic way with (i) uncertainty related to the across-species extrapolation of BLMs and (ii) the relatively high sensitivity of some multi-species toxicity studies.     

Air Change Effectiveness and Pollutant Removal Efficiency during Adverse Mixing Conditions

Abstract The air change effectiveness (ACE), an indicator of the indoor airflow pattern, was measured in twenty-six laboratory experiments. Ventilation air was supplied through induction-type diffusers located in the ceiling and removed through a ceiling mounted return grille. The tracer-gas step-up measurement procedure was employed. In five of the experiments, pollutant removal efficiencies were also measured for simulated pollutant emissions from the floor covering and for simulated emissions from occupants. In experiments with heated supply air, supply airflow rates typical of the minimum supply flow rates of VAV ventilation systems, and 100% outside air, the ACE ranged from 0.69 to 0.89. These results indicate that significant short-circuiting of ventilation air between the supply air diffuser and return air grille does occur under these adverse conditions. Mechanical recirculation of air, so that the supply air contained approximately 50% outside air, increased the ACE by about 0.05. When the supply air was cooled, the ACE ranged from 0.99 to 1.15, adding to existing evidence that short-circuiting is rarely a problem when the building is being cooled. The pollutant removal efficiency for simulated pollutant emissions from the floor covering (PRE_floor) was strongly correlated with ACE (R²= 0.98) and the values of PRE_floor were within approximately 0.1 of the values of ACE. The pollutant removal efficiency for simulated pollutant emissions by occupants varied between workstations and was not as well correlated with the ACE.     

Beyond pixels: Exploiting camera metadata for photo classification

Semantic scene classification based only on low-level vision cues has had limited success on unconstrained image sets. On the other hand, camera metadata related to capture conditions provide cues independent of the captured scene content that can be used to improve classification performance. We consider three problems, indoor-outdoor classification, sunset detection, and manmade-natural classification. Analysis of camera metadata statistics for images of each class revealed that metadata fields, such as exposure time, flash fired, and subject distance, are most discriminative for each problem. A Bayesian network is employed to fuse content-based and metadata cues in the probability domain and degrades gracefully even when specific metadata inputs are missing (a practical concern). Finally, we provide extensive experimental results on the three problems using content-based and metadata cues to demonstrate the efficacy of the proposed integrated scene classification scheme.     

Quantitative risk assessment of Campylobacter in broiler chickens – Assessing interventions to reduce the level of contamination at the end of the rearing period

The European Food Safety Authority (EFSA) has estimated that a proportion ranging from 20% to 30% of campylobacteriosis in humans may be attributed to the consumption of broiler meat and a reduction in the numbers of Campylobacter in the intestines of infected birds at slaughter by 3 log units would reduce the public health risk by at least 90%. In this study, a stochastic model was implemented to reproduce the dynamics of Campylobacter transmission in broiler flocks and explore the effects of several management conditions and/or on-farm mitigation strategies on the estimated level of contamination of infected flocks at slaughter. Results were expressed as ‘proportion of highly contaminated flocks’ (%HCFs) and estimated as a function of the proportion of infected birds in the flock the day of final depopulation and the individual level of contamination in infected birds. The effects of the mitigation strategies aimed at reducing the level of contamination in infected birds were modelled assuming that those effects are exerted on the distribution describing the bacterial load in infected birds. The impact of management conditions such as the adoption of enhanced biosecurity measures (B+) and/or partial depopulation during the production cycle (T+) were quantified using results of an extensive epidemiological study conducted in UK. A standard broiler flock was reproduced and used as baseline to make comparisons and simulate the effects of the mitigation strategies of interest. The baseline model predicted 18.8% probability of HCFs at slaughter. A positive effect ranging from −32.44% to −4.78% was attributed to B+ while T+ had negative effect ranging from +17.55% to +86.70%. When both the effects were tested simultaneously (B+T+), results were not conclusive with %HCFs ranging from −20.21% to +77.65%. When mitigation strategies operating on Campylobacter concentration in intestine were tested, a reduction of 100% and 99.6% in %HFCs were estimated following a generic treatment with bacteriocins and bacteriophages. Reduction in %HCFs as a function of immunization measures were explored and a reduction of 15% in the rate of transmission led to a %HCFs at slaughter reduced by almost 50%. The model was developed to be flexible, easily reproducible, updatable and adaptable to several baseline scenarios. The main parameters and assumptions underlying the baseline model were tested and a sensitivity analysis was performed to identify and discuss the impact that the uncertainty in the baseline information might have on the outcomes.     

Latent risk and trend models for the evolution of annual fatality numbers in 30 European countries

In this paper a unified methodology is presented for the modelling of the evolution of road safety in 30 European countries. For each country, annual data of the best available exposure indicator and of the number of fatalities were simultaneously analysed with the bivariate latent risk time series model. This model is based on the assumption that the amount of exposure and the number of fatalities are intrinsically related. It captures the dynamic evolution in the fatalities as the product of the dynamic evolution in two latent trends: the trend in the fatality risk and the trend in the exposure to that risk. Before applying the latent risk model to the different countries it was first investigated and tested whether the exposure indicator at hand and the fatalities in each country were in fact related at all. If they were, the latent risk model was applied to that country; if not, a univariate local linear trend model was applied to the fatalities series only, unless the latent risk time series model was found to yield better forecasts than the univariate local linear trend model. In either case, the temporal structure of the unobserved components of the optimal model was established, and structural breaks in the trends related to external events were identified and captured by adding intervention variables to the appropriate components of the model. As a final step, for each country the optimally modelled developments were projected into the future, thus yielding forecasts for the number of fatalities up to and including 2020.     

Analytical solutions for exposures and toxic loads in well-mixed shelters in support of shelter-in-place assessments

Understanding the exposure and toxic load for the interior of buildings during and following the passage of an external airborne hazard can be a critical piece of information in deciding the benefit from adopting a shelter-in-place strategy. Whilst numerical methods allow the calculation of such parameters for the general case, analytical solutions allow more rapid assessments to be made and highlight the key parameters more clearly. Analytical expressions are derived for the exposure due to the acute inhalation of toxic chemicals and the associated toxic load as a function of time, external hazard duration and building air change rate assuming a top-hat outdoor concentration profile and no indoor loss mechanism. It is shown that the internal exposure tends to the external exposure at long times for any external concentration profile. Expressions are derived for toxic loads with exponents n=m/2 where 2 ≤ m ≤ 7 is an integer to cover the range of typical values (1 ≤ n ≤ 3.5). At long times the ratio of internal to external toxic load for a top-hat outdoor concentration profile is shown to be a function of the product of the air change rate and the duration of the external hazard.     

Design of challenge testing experiments to assess the variability of Listeria monocytogenes growth in foods

The assessment of the evolution of micro-organisms naturally contaminating food must take into account the variability of biological factors, food characteristics and storage conditions. A research project involving eight French laboratories was conducted to quantify the variability of growth parameters of Listeria monocytogenes obtained by challenge testing in five food products. The residual variability corresponded to a coefficient of variation (CV) of approximately 20% for the growth rate (μ_max) and 130% for the parameter K = μ_max × lag. The between-batch and between-manufacturer variability of μ_max was very dependent on the food tested and mean CV of approximately 20 and 35% were observed for these two sources of variability, respectively. The initial physiological state variability led to a CV of 100% for the parameter K. It appeared that repeating a limited number of three challenge tests with three different batches (or manufacturers) and with different initial physiological states seems often necessary and adequate to accurately assess the variability of the behavior of L. monocytogenes in a specific food produced by a given manufacturer (or for a more general food designation).     

Analysis of indoor PM2.5 exposure in Asian countries using time use survey

Most household fuels used in Asian countries are solid fuels such as coal and biomass (firewood, crop residue and animal dung). The particulate matter (PM), CO, NOx and SOx produced through the combustion of these fuels inside the residence for cooking and heating has an adverse impact on people's health. PM 2.5 in particular, consisting of particles with an aerodynamic diameter of 2.5 μm or less, penetrates deep into the lungs and causes respiratory system and circulatory system diseases and so on. As a result, the World Health Organization (WHO) established guideline values for this type of particulate matter in 2005. In this study, the authors focused on PM 2.5 and estimated indoor exposure concentrations for PM 2.5 in 15 Asian countries. For each environment used for cooking, eating, heating and illumination in which people are present temporarily (microenvironment), exposure concentrations were estimated for individual cohorts categorized according to sex, age and occupation status. To establish the residence time in each microenvironment for each of the cohorts, data from time use surveys conducted in individual countries were used. China had the highest estimate for average exposure concentration in microenvironment used for cooking at 427.5 μg/m³ , followed by Nepal, Laos and India at 285.2 μg/m³, 266.3 μg/m³ and 205.7 μg/m³ , respectively. The study found that, in each country, the PM2.5 exposure concentration was highest for children and unemployed women between the ages of 35 and 64. The study also found that the exposure concentration for individual cohorts in each country was greatly affected by people's use of time indoors. Because differences in individual daily life activities were reflected in the use of time and linked to an assessment of exposure to indoor air-polluting substances, the study enabled detailed assessment of the impact of exposure.     

Estimation of daily inhalation rate in preschool children using a tri-axial accelerometer: a pilot study

The activity of 5- to 6-year-old Japanese children (n = 29) was monitored for 3 consecutive days, including one weekend day, using an ActivTracer tri-axial accelerometer. The daily inhalation rate and time spent in sedentary, light, or moderate to vigorous levels of physical activity (MVPA) were estimated from the accelerometer measurements based on previously developed regression equations. The 3-day mean daily inhalation rate (STPD) was estimated at 8.3 ± 1.4 m³ day⁻¹ in 10 subjects who completed 3 days of monitoring. The time spent in sedentary, light, or MVPA each day was 320, 415, and 81 min day⁻¹, respectively. Analysis of between-day reliability indicated that 3 days of monitoring with the ActivTracer tri-axial accelerometer provided an acceptable estimate of daily inhalation rate (intra-class correlation coefficient [ICC] = 0.892), but low to moderate reliability for the time spent in different levels of activities (ICC = 0.43 to 0.58). We observed a significant difference in the daily inhalation rate between weekdays and the weekend day, possibly due to differences in time spent in MVPA. This finding suggests that a weekend day should be included to obtain more reliable estimates of daily inhalation rate using an accelerometer.     

Mercury exposure and risks from dental amalgam in the US population, post-2000

Dental amalgam is 50% metallic mercury (Hg) by weight and Hg vapour continuously evolves from in-place dental amalgam, causing increased Hg content with increasing amalgam load in urine, faeces, exhaled breath, saliva, blood, and various organs and tissues including the kidney, pituitary gland, liver, and brain. The Hg content also increases with maternal amalgam load in amniotic fluid, placenta, cord blood, meconium, various foetal tissues including liver, kidney and brain, in colostrum and breast milk.Based on 2001 to 2004 population statistics, 181.1 million Americans carry a grand total of 1.46 billion restored teeth. Children as young as 26 months were recorded as having restored teeth. Past dental practice and recently available data indicate that the majority of these restorations are composed of dental amalgam.Employing recent US population-based statistics on body weight and the frequency of dentally restored tooth surfaces, and recent research on the incremental increase in urinary Hg concentration per amalgam-filled tooth surface, estimates of Hg exposure from amalgam fillings were determined for 5 age groups of the US population.Three specific exposure scenarios were considered, each scenario incrementally reducing the number of tooth surfaces assumed to be restored with amalgam. Based on the least conservative of the scenarios evaluated, it was estimated that some 67.2 million Americans would exceed the Hg dose associated with the reference exposure level (REL) of 0.3 μg/m³ established by the US Environmental Protection Agency; and 122.3 million Americans would exceed the dose associated with the REL of 0.03 μg/m³ established by the California Environmental Protection Agency.Exposure estimates are consistent with previous estimates presented by Health Canada in 1995, and amount to 0.2 to 0.4 μg/day per amalgam-filled tooth surface, or 0.5 to 1 μg/day/amalgam-filled tooth, depending on age and other factors.