Terrestrial Testing Services
Ecotoxicology is the study of the toxic effects of a sample on the constituents of an ecosystem. Chemex Ecotoxicology laboratory has a history of providing accurate and reproducible data for regulatory submissions to many industries around the world at a competitive price. Our experienced team of scientists are committed to providing a high quality service utilising the latest methods and techniques at our disposal. Chemex is able to offer all studies with full Good Laboratory Practice (GLP) compliance.
Chemex are one of the few UK laboratories that offer a wide range of marine studies suitable for OCNS (Offshore Chemicals Notification Scheme)/HOCNF (Harmonised Offshore Chemicals Notification Format) purposes. More cost effective screening methods are also available for initial determination of the most suitable chemicals/products to proceed with.
Activated Sludge Respiration Inhibition (OECD 209)
Activated Sludge Respiration Inhibition Test (ASRIT) - Carbon and/or Ammonium Oxidation
This test examines the effect of test substances on the activity of activated sludge microorganisms taken from a sewage works receiving largely domestic sewage. The test can be used to estimate possible effects on a sewage works and the results can be used to set a suitable concentration range for further biodegradation studies. The test substance is added at different concentrations to activated sludge and incubated at 21 ± 2°C under fully aerated conditions for 3 hours. The respiration rate is measured over a 10-minute period using Dissolved Oxygen probes and closed BOD bottles.
Earthworm Acute Toxicity (OECD 207)
Study to assess acute toxicity to Earthworms
Concentrations of test substance are added to a defined artificial loam soil in which adult earthworms are maintained for 14 days. After 7 and 14 days the effects of the test substance on earthworm survival are examined. The results are used to calculate LC50 values and no observed effect concentrations. Reference tests are carried out with chloracetamide in order to check the validity of the test system.
Earthworm Reproduction (OECD 222)
Earthworm reproduction Test (Eisenia fetida)
In general terms, this study is designed to assess the effects of chemicals in soil on the reproductive output of the earthworm species Eisenia fetida (alternatively Eisenia andrei can be used).
Concentrations of test substance are added to a defined artificial medium either by surface spraying or by mixing the material into the soil. Adult worms are added to the soil and removed after 28 days, leaving any juveniles and cocoons to develop in the treated soil. After a further 28 days the numbers of juveniles produced in each vessel at each exposure concentration are counted and compared with the unexposed controls. Significant effects on reproduction are evaluated using appropriate statistical methods (curve fitting and mutiple comparison procedures). Reference studies using carbendazim are used to confirm the sensitivity of the test.
Effects on Sediment Dwelling Organisms - Chironomid (OECD 218)
Chironomid Toxicity Using Spiked Sediment - Freshwater
This Test Guideline is designed to assess the effects of prolonged exposure of chemicals to the sediment-dwelling larvae of the freshwater dipteran Chironomus sp.
First instar chironomid larvae are exposed to at least five concentrations of the test chemical in sediment - water systems. The test substance is spiked into the sediment and first instar larvae are subsequently introduced into test beakers in which the sediment and water concentrations have been stabilised. Chironomid emergence and development rate is measured at the end of the test. The maximum exposure duration is 28 days for C. riparius, C. yoshimatsui, and 65 days for C. tentans. The limit test corresponds to one dose level of 1000 mg/kg. Larval survival and weight may also be measured after 10 days if required (using additional replicates as appropriate). The study report should include the development time and the total number of fully emerged midges (sex and number are recorded daily), the observation of any abnormal behaviour the number of visible pupae that have failed to emerge and any egg masses deposition. The data are analysed either by using a regression model in order to estimate the concentration that would cause x % reduction in emergence or larval survival or growth, or by using statistical hypothesis testing to determine a NOEC/LOEC.
Effects on Sediment Dwelling Organisms - Chironomid (OECD 219)
Chironomid Toxicity Using Spiked Water - Freshwater
This study is designed to assess the effects of prolonged exposure of chemicals to the sediment-dwelling larvae of the freshwater dipteran Chironomus sp.
First instar chironomid larvae are exposed to at least five concentrations of the test chemical in sediment-water systems. The test starts by placing first instar larvae into the test beakers containing the sediment-water system and subsequently spiking the test substance into the water. Chironomid emergence and development rate is measured at the end of the test. The maximum exposure duration is 28 days for C. riparius, C. yoshimatsui, and 65 days for C. tentans. Larval survival and weight may also be measured after 10 days if required (using additional replicates as appropriate). The study report should include the development time and the total number of fully emerged midges (sex and number are recorded daily), the observation of any abnormal behaviour, the number of visible pupae that have failed to emerge and any egg masses deposition. The data are analysed either by using a regression model in order to estimate the concentration that would cause x % reduction in emergence, larvae survival or growth, or by using statistical hypothesis testing to determine a NOEC/LOEC.
Effects on Soil Microorganisms (OECD 216)
Effects on Soil Microorganisms - Nitrogen Transformation Test
This test method is designed to investigate the long-term effects of chemicals, after a single exposure, on nitrogen transformation activity of soil microorganisms.
Sieved soil is amended with powdered plant meal and either treated with the test substance or left untreated. For agrochemicals, a minimum of two test concentrations are recommended (five for non agrochemicals) and these should be chosen in relation to the highest concentration anticipated in the field. The soil is divided into three portions of equal weight (six for non agrochemicals). Two portions are mixed with the carrier containing the product (five for non agrochemicals), and the other is mixed with the carrier without the product (control). A minimum of three replicates for both treated and untreated soils is recommended. After 0, 7, 14 days and 28 days of incubation, samples of treated and control soils are extracted with an appropriate solvent, and the quantities of nitrate in the extracts are determined. All tests run for at least 28 days. If, on the 28th day, differences between treated and untreated soils are equal to or greater than 25%, measurements are continued to a maximum of 100 days. Results from tests with multiple concentrations are analysed using a regression model, and the ECx values are calculated.
Effects on Soil Microorganisms (OECD 217)
Soil Microorganisms - Carbon Transformation Test
This Test Guideline describes a laboratory test method designed to investigate long term potential effects of a single exposure of agrochemicals/non agrochemicals on carbon transformation activity of soil microorganisms.
A minimum of two test concentrations are recommended for agrochemicals (five for non agrochemicals). Sieved soil is divided into portions of equal weight (three for agrochemicals, six for non agrochemicals) including portions mixed with the carrier containing the product, and the control. A minimum of three replicates for both treated and untreated soils is recommended. After 0, 7, 14 and 28 days incubation, samples of treated and control soils are mixed with glucose, and glucose-induced respiration rates are measured for 12 consecutive hours. Respiration rates are expressed as carbon dioxide released or oxygen consumed. The mean respiration rate in the treated soil samples is compared with that in control and the percent deviation of the treated from the control is calculated. All tests run for at least 28 days. If, on the 28th day, differences between treated and untreated soils are equal to or greater than 25 % measurements are continued in 14 day intervals for a maximum of 100 days. Results are analysed using a regression model, and the ECx values are calculated. When the difference in respiration rates between the lower treatment and control is equal to or less than 25 % at any sampling time after day 28, agrochemicals can be evaluated as having no long-term influence on carbon transformation in soils. The EC50, EC25 and/or EC10 values are used for non agrochemicals.
Estimation of the Adsorption Coefficient on Soil and Sewage Sludge (OECD 121)
Estimation of the Adsorption Coefficient (Koc) on Soil and Sewage Sludge using HPLC (OECD 121)
An important parameter in the sorption behaviour of substances is the adsorption coefficient (Koc). This is defined as the ratio between the concentration of the substance in the soil/sludge and the concentration of the substance in the aqueous phase at adsorption equilibrium. The adsorption coefficient normalised to the organic content of the soil Koc is a useful indicator of the binding capacity of a chemical on organic matter of soil and sewage sludge and allows comparisons to be made between different chemicals.
The experimental method uses High Performance Liquid Chromatography (HPLC) for the estimation of the adsorption coefficient (Koc) in soil and sewage sludge. While passing through the column in the mobile phase the test substance interacts with the stationary phase. As a result of partitioning between mobile and stationary phases the test substance is retarded. The dual-composition of the stationary phase having polar and non-polar sites allows for the interaction of polar and non-polar groups of a molecule in a similar way as is the case for organic matter in soil or sewage sludge matrices. This enables the relationship between the retention time on the column and the adsorption coefficient on organic matter to be established.
Soil Microbial Biomass
Soil Microbial Biomass (BS 7755 / Anderson Domsch - Fumigation/Extraction Method)
The measurement of soil microbial biomass is one of the most reliable procedures commonly used for a better comprehension of the nutrient cycle in soil. Among the methods available, the Chloroform Fumigation Extraction method (Vance et al, 1987) is more commonly used due to its simplicity and applicability for wide group of soils.
The microbial biomass carbon is determined as the difference between the fumigated and non-fumigated organic carbon contents multiplied by a proportionality factor. This factor comes from the work of Wu et al (1990) and Vance et al (1987) who determined a linear relationship between biomass carbon and extractable carbon due to fumigation.