Continuing injecting risk behaviour: results from the Amsterdam Cohort Study of drug users.

AIMS: To give a detailed description of injection-related risk behaviours, and to estimate the relative importance of these behaviours with regard to HIV transmission. DESIGN: The present study was part of the Amsterdam Cohort Study of drug users. SETTING: In Amsterdam, a city with extensive preventive measures, large HIV-risk reductions have taken place, but no further decreases have occurred since 1991. PARTICIPANTS AND MEASUREMENTS: A detailed questionnaire on injecting risk behaviour was completed by a cross-section of participants in 1992/93 (n = 168). Among 48 HIV-seroconverters, a questionnaire was completed concerning possible HIV-transmission route. FINDINGS: Of 96 HIV-negative participants, 23% deliberately borrowed a used syringe, 18% reported possible "accidental" borrowing, 9% front/backloading, 4% simultaneous injection, and 32% possible sharing of ancillary equipment. Of deliberate borrowers, 64% borrowed from a person with unknown or positive HIV serostatus, and 81% did not appropriately clean the equipment; 79% borrowed in the absence of serious withdrawal symptoms. Risk factors differed for deliberate and 'accidental' borrowing. Among the HIV seroconverters, the most likely transmission route was borrowing in 29% of cases, front/backloading in 8%, borrowing or front/backloading in 21%, unprotected sexual contact in 23% (mainly with regular partner) and either injecting or sexual risk in 13%. Women were much more likely to report sexual transmission (p = 0.016). Borrowing was admitted by 43% before, and 64% after awareness of HIV-seroconverion. CONCLUSIONS: As the injecting risk is high, usually deliberate, and often in the absence of withdrawal symptoms, further prevention seems difficult. Although deliberate borrowing is the main risk for HIV seroconversion, unprotected sexual contacts and front- and backloading may be more important than previously thought in Amsterdam. Under-reporting of borrowing is probably substantial, but does not alter the above conclusions.

Effect of ambient oxygen concentration upon the acute toxicity of chlorophenols and heavy metals to the groundwater copepod Parastenocaris germanica (Crustacea).

Acute static toxicity experiments have been performed under normoxic and hypoxic conditions. The test animals used were adults of the groundwater-adapted copepod Parastenocaris germanica. The animals originated from a sandy, gravelly phreatic aquifer of the Meuse valley in The Netherlands. Toxicants applied were pentachlorophenol, 3,4-dichlorophenol, zinc, and cadmium. The results were statistically evaluated by a log-logistic model. LC50 and LC5 values with 95% confidence limits were calculated. Response models of application under both oxygen conditions were compared. The influence of ambient oxygen concentration on sensitivity appeared to be very small; only in the case of pentachlorophenol were hypoxic and normoxic models slightly but significantly different. Comparisons with the sensitivity of other organisms are made and the results are discussed against the specific physiological adaptations of the organisms to groundwater conditions.