Application of the headspace CO2 method (ISO 14 593) to the assessment of the ultimate biodegradability of surfactants: results of a calibration exercise.

In the recent review of the control of marketing surfactants used in detergents, the EU decided to increase the severity of the testing procedure by using the criterion of ultimate biodegradability (mineralization) rather than primary biodegradation (removal of the parent molecule) to ensure that possible harmful organic metabolites do not reach the environment. The relatively new ISO headspace CO2 test, considered to be an improvement on the OECD 301B (Sturm CO2) test was chosen. The method was subjected to a ring test by 11 laboratories using one of each of four classes of surfactants plus a poorly degradable reference surfactant; all laboratories satisfactorily applied the method. The necessary addition of silica gel to the medium containing the cationic surfactant, known as a class to be more inhibitory than other classes, was confirmed as a technique for avoiding inhibition of the inoculum. The biodegradability of the surfactants was in general agreement with results reported in the literature and the often reported variable values of % inorganic carbon (IC) produced of the theoretical was found. The anionic and cationic surfactants were readily biodegradable (%IC > 60), the non-ionic surfactant was well below the pass value, while the amphoteric was borderline. The IC production by the blank controls, one of the validity criteria, was about 0.3 mg C/100 ml test medium, equivalent to 3 mg C/l, as recommended in the ISO text. Mild conditions of pre-exposure of the inoculum to the test surfactant did not produce consistent worthwhile effects on either the percentage biodegradation or on its variability.

An 'inherent' biodegradability test for oil products: description and results of an international ring test. CONCAWE Biodegradation Task Force.

Current test guidelines for assessing 'inherent' (potential) biodegradability were designed for water-soluble, organic compounds of low volatility and are unsuitable for most oil products. It was against this background, that CONCAWE (the oil companies' European organisation for environment, health and safety) formed a task force to develop a standard test protocol for assessing the 'inherent' biodegradability of oil products.

Keratinocyte growth factor therapy in murine oleic acid-induced acute lung injury.

Alveolar type II (ATII) cell proliferation and differentiation are important mechanisms in repair following injury to the alveolar epithelium. KGF is a potent ATII cell mitogen, which has been demonstrated to be protective in a number of animal models of lung injury. We have assessed the effect of recombinant human KGF (rhKGF) and liposome-mediated KGF gene delivery in vivo and evaluated the potential of KGF as a therapy for acute lung injury in mice. rhKGF was administered intratracheally in male BALB/c mice to assess dose response and time course of proliferation. SP-B immunohistochemistry demonstrated significant increases in ATII cell numbers at all rhKGF doses compared with control animals and peaked 2 days following administration of 10 mg/kg rhKGF. Protein therapy in general is very expensive, and gene therapy has been suggested as a cheaper alternative for many protein replacement therapies. We evaluated the effect of topical and systemic liposome-mediated KGF-gene delivery on ATII cell proliferation. SP-B immunohistochemistry showed only modest increases in ATII cell numbers following gene delivery, and these approaches were therefore not believed to be capable of reaching therapeutic levels. The effect of rhKGF was evaluated in a murine model of OA-induced lung injury. This model was found to be associated with significant alveolar damage leading to severe impairment of gas exchange and lung compliance. Pretreatment with rhKGF 2 days before intravenous OA challenge resulted in significant improvements in PO2, PCO2, and lung compliance. This study suggests the feasibility of KGF as a therapy for acute lung injury.

A respirometric method for the assessment of ready biodegradability: results of a ring test.

A collaborative exercise involving twelve laboratories was organized for the European Economic Community to check the validity of an enclosed respirometric method for assessing the ready biodegradability of test chemicals, including insoluble substances. The method, based partly on the OECD-Japanese Ministry of International Trade and Industry (MITI) I method (301C) and partly on the U.K. method, allowed the use of a less restrictive, natural inoculum and a wider variety of respirometers than the original MITI I method. Eight compounds of a wide range of degradative behavior were tested over an incubation period of 28 days. The agreement between participating laboratories in the lag period before biodegradation started and in the proportions of theoretical oxygen uptake achieved was at least as good as in other ring tests; it is proposed that the method be accepted. Differences in behavior of pentaerythritol reported here and in the literature are examined and suggestions for future study are discussed.

A mathematical model of biodegradability screening tests as an aid to interpretation of observed results.

A mathematical model, based on a modification of the Michaelis--Menten and Monod equations describing bacterial growth, has been used to predict the course of removal of the organic substrates in the modified OECD and other screening tests. A range of initial concentrations of bacteria in the inoculum has been selected, using published data on the total bacterial count in secondary sewage effluents and activated sludge, to simulate the wide range of volumes of these materials used in practice. The arbitrary definition of ready biodegradability adopted by the OECD, that is, 5 to the equivalent of 70% DOC removal in not more than 10 days in a total incubation period of 28 days, is expressed in terms of inoculum size and kinetic constants. Modifications are proposed to the screening test with the object of making it more useful and realistic in predicting whether or not a chemical will be removed in sewage treatment.