Toxic effects of some major polyaromatic hydrocarbons found in crude oil and aquatic sediments on Scenedesmus subspicatus.

The green alga, Scenedesmus subspicatus was exposed for 7 days to a series of PAHs (polyaromatic hydrocarbons) of increased molecular weight from two to five rings [naphthalene (Nap), anthracene (Ant), phenanthrene (Phe), pyrene (Pyr) and benzo(a)pyrene (BaP)]. The toxicity measured as population growth inhibition by individual PAH to the S. subspicatus followed the order: BaP>Pyr>Ant>Phe>Nap. These results confirmed that the toxicity potential of PAHs seems to be strongly influenced by their physico-chemical properties (aqueous solubility, K(ow), coefficient of volatilization, etc.) and the conditions of algae culture (light, presence of nitrate ions, etc.). Consequently, Nap, Phe and Ant having low k(ow) values and low coefficient of volatilization values were less toxic than BaP with the highest k(ow) value, indicating for example why Nap with the lowest EC(50) value was nearly 2 x 10(5) times lower than that of BaP. Moreover, nitrate ions seemed to act directly on the degree of hydroxylated radical reactivity of PAHs, since BaP always remained the most toxic of the compounds tested. The results were also agreed with the QSAR model for toxicity prediction of PAHs to many aquatic organisms.

Freshwater microcosms-based assessment of eco-toxicological effects of a chemical effluent from the Pilcam industry in Cameroon.

We studied the acute toxicity of a raw effluent from a battery manufacturing plant (Pilcam) in Douala, Cameroon, to a freshwater fish (Oreochromis niloticus), and subsequently evaluated its sub-acute effects on water quality and the biota in freshwater microscosms. The acute toxicity test was based on 96 hrs static renewal bioassays that resulted in 96-h LC50 and LC90 values of 16 and 20.7% (v/v), respectively. The sub-acute experiments were conducted by exposing several species of aquatic organisms (plankton, macroinvertebrates and mollusks) to lower effluent concentrations [1.6%, 8.0%, 16% (v/v)] for six weeks, and monitoring their survival rates, as well as the physical and chemical characteristics of water. These concentrations were based on 10%, 50%, and 100% of the 96 h - median lethal concentrations (LC50) of the effluent to the freshwater fish, Oreochromis niloticus. Significant effects on functional parameters, such as, chlorophyll-a and total protein could not be demonstrated. However, the activity of alkaline phosphatase was significantly inhibited at all concentrations tested. Phytoplankton, zooplankton, macro-invertebrate communities and snails were negatively affected by the effluent application at concentrations ? 8% (v/v), with chlorophyta, ciliates, ostracoda, annelida, planaria and snails being the most sensitive groups. The snails were eliminated after 24 h exposure from microcosms treated with effluent at concentration ? 8% (v/v). Effluent exposure also caused significant effects on water quality parameters (DO, pH, hardness, conductivity, color, turbidity, ammonia) in general at concentrations ? 8% (v/v). Temperature and alkalinity were not significantly affected. Overall, data from this research indicate that a dilution of the Pilcam effluent down to 1.6% does not provide protection against chronic toxicity to aquatic organisms. Further studies are needed to determine the no observable adverse effect level (NOAEL), as well as a chronic reference concentration for this effluent.

Accumulation kinetics of polycyclic aromatic hydrocarbons adsorbed to sediment by the mollusk Corbicula fluminea.

The accumulation kinetics in the freshwater mollusk Corbicula fluminea were measured for sediment-associated selected polycyclic aromatic hydrocarbons (PAHs), namely, anthracene (Ant), phenanthrene (Phe), pyrene (Pyr), and benzo [a] pyrene (BaP). The desorption from sediment to water was not only related to water solubility, but also depended on structural and physicochemical properties of PAHs (molecular weight, molecular area, octanol/water partition coefficient Kow). Uptake of PAHs by mollusks was very fast in the first 24 h and maximum for low-molecular-weight compounds. Then animal concentrations decreased significantly after the first day for Ant and Phe, after the second day for Pyr, and after the second week for BaP (at this time the BaP concentration was higher than concentrations of the other PAHs). The kinetic data suggest that PAH uptake is related to desorption from sediment particles. Log PAH uptake is inversely related to log Kow. Bioavailability of sediment-sorbed PAHs declined with contact time between sediment and animals. Assimilation from ingested material may be significant for the more strongly sorbed compound (BaP). PAHs with low Kow values become biologically unavailable more rapidly and more efficiently excreted.

Relationships between formation of micronuclei and DNA adducts and EROD activity in newts following exposure to benzo(a)pyrene.

The aim of this study was to determine whether the micronucleus test, using the larvae of a lower invertebrate, the newt Pleurodeles waltl, is suitable for evaluating the overall genotoxicity of polluted water (AFNOR Standard, 1992). The study used the pollutant model benzo(a)pyrene (BaP). After having shown that BaP is metabolized by the larvae, the test was carried out under standard AFNOR conditions. We investigated the relationship between the BaP concentration, spectrofluorometric measurement of liver EROD activity, and two genotoxicity biomarkers: DNA adduct production (32P-postlabeling detection) and micronucleus formation in red blood cells (RBCs) (number of micronucleated RBCs per 1,000). A dose effect was found for all three biomarkers, which were seen to be linearly correlated showing that the biochemical mechanisms occurring in the newt larvae exposed to BaP are similar to those described in higher vertebrates. This result confirms the utility of the test for the evaluation of the overall hazard of a given aquatic environment.

Amphibian micronucleus test in vivo: evaluation of the genotoxicity of some major polycyclic aromatic hydrocarbons found in a crude oil.

The micronucleus test using erythrocytes of Pleurodeles waltl larvae (Amphibia, Salamandridae) was used to detect the possible genotoxicity of four polycyclic aromatic hydrocarbons (naphthalene, anthracene, phenanthrene and benzo[a]pyrene), which represent a major fraction of crude oil. Larvae were reared in water containing the test compound and the levels of micronucleated red blood cells were compared with those found in larvae reared in control water. The results are compared with published data from other tests used to evaluate the clastogenic or mutagenic properties of compounds. The results obtained confirm that benzo[a]pyrene has a strong genotoxic potential, whereas the genotoxicity of naphthalene is weak; in contrast, anthracene and phenanthrene gave a negative response.