Trace elements in the human environment: Problems and risks

Early studies on the possible influences of environmental geochemistry and health were concerned with major diseases such as cancer or multiple sclerosis. They were generally confined to simple comparisons of geochemical and epidemiological maps and corresponding rural areas. Subsequently, studies of dental health produced evidence for the roles of environmental fluoride, selenium, molybdenum and lead in the aetiology of caries. In recent decades lead has been closely studied. Most people in the western world live in urban areas, rather than rural areas, and research on lead has yielded much information on the distribution of the element in streets, parks and gardens of cities and in the home environment. The role of lead in human health has thereby been better understood. Cadmium, selenium and aluminium are good candidates for future study but success will depend on applying appropriate methods of investigation and here the experiences from research on lead are a valuable model to follow.This paper is based on a keynote lecture at the start of the SEGH conference.     

Insect chemical communication: Pheromones and exocrine glands of ants

Summary Chemical communication plays a very important role in the lives of many social insects. Several different types of pheromones (species-specific chemical messengers) of ants have been described, particularly those involved in recruitment, recognition, territorial and alarm behaviours. Properties of pheromones include activity in minute quantities (thus requiring sensitive methods for chemical analysis) and specificity (which can have chemotaxonomic uses). Ants produce pheromones in various exocrine glands, such as the Dufour, poison, pygidial and mandibular glands. A wide range of substances have been identified from these glands.     

Intraspecific brood adoption in convict cichlids : a mutual benefit

Summary Convict cichlids (Cichlasoma nigrofasciatum) are biparental, substrate brooding cichlid fish which have extended care of their eggs, larvae (wrigglers) and free-swimming young (fry). Field observations indicate that intraspecific brood adoption of fry occurs frequently under natural conditions. Of 232 broods 29% contained foreign fry and of 232 broods 15% were identified as fry donors. Foreign fry were usually of similar size to or smaller than the host brood fry. Experimental fry transfers showed that parents accept foreign fry smaller than their own but immediately reject or eat foreign fry larger than their own. A predation experiment showed that within a mixed brood, smaller fry are eaten more often than larger fry. Thus, accepting foreign fry may benefit parents through the dilution effect and through a differential predation effect. In comparison with intact families, broods from which the male parent was removed were less likely to reach independence, had fewer fry surviving to independence, and had a greater probability of having some fry transferred to neighbouring broods. We propose that intraspecific brood adoption in convict cichlids is mutually beneficial to the adult donors and recipients. Correspondence to: B.D. Wisenden     

Interactive pollutants and joint abatement costs: Achieving water quality standards with effluent charges

This paper extends earlier work on the standards and prices approach to pollution control by considering simultaneously spatial considerations, interactive pollutants, and joint abatement costs. The form of environmental constraints appropriate to water pollution problems is discussed in detail and the implications for the standards and prices approach to water pollution control are assessed. The presence of interactive pollutants and joint abatement costs is shown to have important implications for both the theoretical properties and the implementation of the standards and prices approach.     

Data handling and pattern recognition for metal contaminated soils

In the laboratory sciences good experimental design minimises the effects of any disturbing variables so that hypotheses are amenable to to relatively unambiguous testing. But in the field sciences such variables cannot be controlled and data are inherently variable. Subsequent hypothesis testing must rely on a careful statistical interpretation of noisy data. This paper describes one systematic approach to interpreting the results from surveys of metal contaminated soils. Since contaminating metals are also present naturally in soil, anthropogenic excesses are recognised through statistical tests on the data. The nature of pollution processes also leads to the generation of distinct spatial patterns which may be evaluated through appropriate computergraphic techniques.     

Antibiotic resistance analysis of fecal coliforms to determine fecal pollution sources in a mixed-use watershed

Antibiotic resistance analysis was performed on fecal coliform(FC) bacteria from a mixed-use watershed to determine thesource, human or nonhuman, of fecal coliform contamination. The study consisted of discriminant analysis of antibioticresistance patterns generated by exposure to fourconcentrations of six antibiotics (ampicillin, gentamicinsulfate, kanamycin, spectinomycin dihydrochloride,streptomycin sulfate, and tetracycline hydrochloride). Areference database was constructed from 1125 fecal coliformisolates from the following sources: humans, domestic animals(cats and dogs), agricultural animals (chickens, cattle, andhorses), and wild animals. Based on similar antibioticresistance patterns, cat and dog isolates were grouped asdomestic animals and horse and cattle isolates were grouped aslivestock. The resulting average rate of correctclassification (ARCC) for human and nonhuman isolates was94%. A total of 800 FC isolates taken from the watershedduring either a dry event or a wet event were classifiedaccording to source. Human sources contribute a majority(>50%) of the baseflow FC isolates found in the watershed inurbanized areas. Chicken and livestock sources areresponsible for the majority of the baseflow FC isolates foundin the rural reaches of the watershed. Stormwater introducesFC isolates from domestic (16%) and wild (21%) sourcesthroughout the watershed and varying amounts (up to 60%) fromchicken and livestock sources. These results suggest thatantibiotic resistance patterns of FC may be used to determinesources of fecal contamination and aid in the direction ofwater quality improvement.