Lead poisoning.

Lead poisoning is the most common disease of environmental origin in the United States today. Adult lead poisoning results primarily from exposure by inhalation in the workplace. Pediatric lead poisoning results principally from the ingestion of lead from environmental media, including paint chips, dust, soil, drinking water, ceramics, and medications. Lead is toxic to many organ systems, among them developing erythrocytes, the kidneys, and the nervous system. Lead-induced toxicity to the central nervous system causes delayed development, diminished intelligence, and altered behavior. In young children, this effect has been demonstrated convincingly to occur at blood lead levels between 10 and 20 micrograms per dl. The Centers for Disease Control and Prevention has recommended that a blood lead level of 10 micrograms per dl or higher be considered evidence of increased lead absorption, and the National Academy of Sciences has concurred in that recommendation. Unresolved issues in need of further study include the frequency of screening young children for lead, the question of whether women should be offered screening for lead before conceiving a pregnancy, the role of x-ray fluorescence analysis in assessing lead in bone, and the appropriate legislative response of the United States government to lead-based paint abatement.     

Lead inhibition of enzyme synthesis in soil.

Addition of 2 mg of Pb2+/g of soil concident with or after amendment with starch or maltose resulted in 75 and 50% decreases in net synthesis of amylase and alpha-glucosidase, respectively. Invertase synthesis in sucrose-amended soil was transiently reduced after Pb2+ addition. Amylase activity was several times less sensitive to Pb2+ inhibition than was enzyme synthesis. In most cases, the rate of enzyme synthesis returned to control (Pb2+) values 24 to 48 h after the addition of Pb. The decrease in amylase synthesis was paralleled by a decrease in the number of Pb-sensitive, amylase-producing bacteria, whereas recovery of synthesis was associated with an increase in the number of amylase-producing bacteria. The degree of inhibition of enzyme synthesis was related to the quantity of Pb added and to the specific form of lead. PbSO4 decreased amylase synthesis at concentrations of 10.2 mg of Pb2+/g of soil or more, whereas PbO did not inhibit amylase synthesis at 13 mg of Pb2+/g of soil. Lead acetate, PbCl2, and PbS reduced amylase synthesis at total Pb2+ concentrations of 0.45 mg of Pb2+/g of soil or higher. The results indicated that lead is a potent but somewhat selective inhibitor of enzyme synthesis in soil, and that highly insoluble lead compounds, such as PbS, may be potent modifiers of soil biological activity.     

Lead mineral transformation by fungi.

Pyromorphite (Pb5(PO4)3Cl), the most stable lead mineral under a wide range of geochemical conditions [1], can form in urban and industrially contaminated soils [2] [3] [4] [5]. It has been suggested that the low solubility of this mineral could reduce the bioavailability of lead, and several studies have advocated pyromorphite formation as a remediation technique for lead-contaminated land [3] [5] [6], if necessary using addition of phosphate [6]. Many microorganisms can, however, make insoluble soil phosphate bioavailable [7] [8] [9] [10], and the solubilisation of insoluble metal phosphates by free-living and symbiotic fungi has been reported [11] [12] [13] [14] [15]. If pyromorphite can be solubilised by microbial phosphate-solubilising mechanisms, the question arises of what would happen to the released lead. We have now clearly demonstrated that pyromorphite can be solubilised by organic-acid-producing fungi, for example Aspergillus niger, and that plants grown with pyromorphite as sole phosphorus source take up both phosphorus and lead. We have also discovered the production of lead oxalate dihydrate by A. niger during pyromorphite transformation, which is the first recorded biogenic formation of this mineral. These mechanisms of lead solubilisation, or its immobilisation as a novel lead oxalate, have significant implications for metal mobility and transfer to other environmental compartments and organisms. The importance of considering microbial processes when developing remediation techniques for toxic metals in soils is therefore emphasised.     

Lead accumulation in the aquatic fern Azolla filiculoides.

In this study, we characterized lead (Pb2+) accumulation and storage by the aquatic fern Azolla filiculoides. Lead precipitates were detected in the vacuoles of mesophyll cells of Azolla plants cultured for 6 d in rich growth medium containing 20 mg l(-1) Pb2+. Energy dispersive spectroscopy (EDS) analysis of the relative element content of leaves collected from these plants revealed a 100% increase in the levels of P, S, Na and Ca and a 40% decrease in Mg and Cl compared to the untreated plants. Both Azolla whole plants and isolated apoplasts were incubated for 6 d in 20 mg l(-1) Pb2+. Lead content in the whole plant composed 0.37%, 2.3% and 1.8% of the dry weight after 2, 4 and 6 d of growth, respectively, while the isolated Azolla apoplast contained 0.125%, 1.22% and 1.4% Pb2+, respectively. Lead content in Azolla whole plant increase by 200%, 100% and 22% after 2, 4 and 6 d of growth, respectively, when compared to Azolla apoplast. Dark, electron dense deposits of lead were observed in light and transmission electron microscope in leaf cells treated with lead. All the observed lead deposits were localized in vacuoles while larger lead deposits were found in mature leaves than in young leaves. No lead deposits were found in cells of the cyanobiont Anabaena when the plants were exposed to similar conditions. Activity and content of V-H+-ATPase were studied in Azolla plants grown in the presence of 20, 40 and 80 mg l(-1) of lead for a period of 4 d. Activity of V-H+-ATPase was increased by 190%, 210% and 220%, respectively, but the content of V-H+-ATPase was reduced by all lead concentrations.     

Manchester air disaster.

On 22 August 1985 a fire occurred on a Boeing 737 jet airliner at take off at Manchester Airport. One hundred and thirty seven passengers and crew were on board. Fifty two passengers died on the aircraft, 85 escaped. Most survivors had minor physical injuries, but 15 required admission to hospital because of smoke inhalation and two of these had severe burns. At presentation only one survivor required ventilation but within 12 hours a further five required ventilation. Although initially patients suffering from smoke inhalation may seem relatively well, lung function may deteriorate rapidly in the first 24 hours. Careful organisation and regular practice of procedures to deal with a major accident are essential to be able to respond adequately to such an event.