Assessment of potential health risk for inhabitants living near a former lead smelter. Part 2: site-specific human health risk assessment of Cd and Pb contamination in kitchen gardens

Metal contamination of urban soils and homegrown products has caused major concern. In Part 1, we investigated the long-term effects of a former smelter on the degree of kitchen garden-soil contamination and the quality of the homegrown vegetables from these gardens. The results showed that the soils retained a high level of contamination and that a large proportion of the vegetables produced did not comply with the legislation on the levels of metals allowed for human consumption. The present study aims to assess the associated potential health risk to local inhabitants through consumption of homegrown vegetables and ingestion of soil particles using a land use-based approach. For lead (Pb), the standard hazard quotient (HQ)-based risk assessment method was used to determine the HQ. For cadmium (Cd), the approach consisted of calculating the HQs and then deriving site-specific assessment criteria (SSAC) using the SNIFFER method. The results suggested that the exposure pathways considered should not engender any form of deleterious health effects for adults. For children, Pb was the main concern and induced a relatively high health risk through soil particle ingestion, and most total soil Cd concentrations exceeded the derived SSAC, in particular, through consumption of vegetables. The metal bioaccessibility in soils was incorporated into the methods to establish more realistic risk assessment measures. This study proposes an approach to integrate different human health risk assessment methods. Further investigations should complete the assessment to improve risk determination, e.g., the determination of metal bioaccessibility in vegetables.     

Worker reproduction in honey-bees (Apis) and the anarchic syndrome: a review

Honey-bees, Apis, are an important model system for investigating the evolution and maintenance of worker sterility. The queen is the main reproductive in a colony. Workers cannot mate, but they can lay unfertilized eggs, which develop into males if reared. Worker reproduction, while common in queenless colonies, is rare in queenright colonies, despite the fact that workers are more related to their own sons than to those of the queen. Evidence that worker sterility is enforced by 'worker policing' is reviewed and worker policing is shown to be widespread in Apis. We then discuss a rare behavioural syndrome, 'anarchy', in which substantial worker production of males occurs in queenright colonies. The level of worker reproduction in these anarchic colonies is far greater than in a normal queenright honey-bee colony. Anarchy is a counterstrategy against worker policing and an example of a 'cheating' strategy invading a cooperative system.     

Distinguishing Ecotoxic Effects of Environmental Pollutants

Environmental fluctuations and biological variability affect the establishment of baseline data in studying the ecotoxic effects of pollutants. Since substantial fluctuations are recorded for various ecological indices, it becomes problematic to establish whether an observed change in some ecological parameters represents a variation caused by presence of a pollutant, or represents 'natural' fluctuations inherent in the ecosystem.Thus, ability to predict ecotoxic effect lies at the base of the diagnosis. Such diagnosis should employ characteristics that reflect the integrated response of component populations to perturbations and as well provide a comprehensive picture of ecosystem 'status'. Measurements become authentic and acceptable only when compared with normal values of the numerical parameter in question.     

Toxicity of various anions associated with methoxyethyl methyl imidazolium-based ionic liquids on Clostridium sp

We investigated the effects on the growth of the anaerobic bacterium, Clostridium sp., of the ionic liquid, 1-methoxyethyl-3-methyl imidazolium [MOEMIM]⁺, derived from imidazolium cation and paired with one of a variety of counter-ions, viz., tetrafluoroborate [BF₄]^-, hexafluorophosphate [PF₆]^-_, trifluoroacetate [CF₃COO]^-, bis(trifluoromethane)sulfonamide [Tf₂N]^-, methane sulfonate [OMS], and 1-butyl-3-methyl imidazolium tetrafluoroborate [BMIM][BF₄]. These anions, in association with [MOEMIM]⁺ lowered the growth rate of the bacterium, showing the following trend: [Tf₂N]^- ≧ [PF₆]^- > [BF₄]^- > [CF₃COO]^- > [OMS]⁻. Anions incorporating fluorine were more toxic than those without it, and their toxicity rose with an increase in the number of fluorine atoms. Also, [MOEMIM]⁺[BF₄]^- was less toxic than [BMIM]⁺[BF₄]^-, probably due to the presence of a methoxyethyl functional group integrated in the cation side chain.     

Short-term interactions of aniline and benzidine with three soils in both natural and artificial matrices

The fate of aromatic amines in natural systems is important to understand due to the persistence and toxicity of these chemicals. Laboratory experiments were performed to elucidate aniline and benzidine behavior in silty-clay, sandy loam, and sandy soils, and six background matrices (rainwater, 12.5 mM CaCl(2), 25 mM CaCl(2), and each passed through soil columns). The goals of this study were to test the validity of using CaCl(2) as a laboratory simulation for rainwater and to observe how short-term sorption (24 h) of aniline and benzidine changed when these solutions were passed through soil columns. Results indicated that neither CaCl(2) solution exactly predicted the sorption of these chemicals in corresponding rainwater solutions, likely due to varying soil properties that influenced the sorption mechanisms. Statistical analyses revealed that the passage of rainwater or CaCl(2) solutions through soil columns did not significantly affect the sorption of aniline or benzidine. Cation exchange and solubility plots were created to identify the sorption mechanisms taking place in the short-term batch experiments. These plots indicated that cation exchange played a role in the sorption of both aniline and benzidine under all conditions, while solubility plots showed higher correlations for benzidine, a consequence of its lower aqueous solubility.     

Why do honey-bee (Apis millifera) foragers transfer nectar to several receivers? Information improvement through multiple sampling in a biological system

The task of nectar foraging in honey-bees is partitioned between foragers and receivers. Foragers typically transfer a nectar load in the nest as sub-loads to several receivers rather than as a single transfer. Foragers experience delays in finding receivers and use these delays to balance the number of foragers and receivers. A short delay results in the forager-recruiting waggle dance whereas a long delay results in the receiver-recruiting tremble dance. Several nectar transfers increase the cost of this system by introducing additional delays in finding extra receivers. We tested four hypotheses to explain the occurrence of multiple transfer. We found no evidence that multiple transfer is due to different crop capacities of foragers and receivers or that it results from extensive trophallactic interactions with nest-mates. Receiver bees frequently evaporate nectar in their mouthparts to hasten the production of honey. The suggestion has been made that multiple transfer is driven by receivers who take partial loads from foragers to enhance nectar evaporation. An alternative suggestion is that foragers drive multiple transfer to gain better information on the balance of foragers and receivers. Multiple sampling of the delay in finding a receiver reduces the standard deviation of the delay mean and so provides foragers with better information than is provided by a single delay. The enhanced-evaporation hypothesis predicts that receivers break foragers' first transfer whereas the information improvement hypothesis predicts foragers break their first transfers. Furthermore, only the information improvement hypothesis predicts a high level of multiple receptions. Data on transfer break-off and receiver behaviour strongly support the information improvement hypothesis and reject the enhanced-evaporation hypothesis. We suggest that multiple transfer is an adaptive sampling mechanism, which improves foragers' information on colony work allocation, and that multiple sampling is a common feature of social insect societies.