Des Connell

Toxicology and Risk Assessment of Freshwater Cyanobacterial (Blue-Green Algal) Toxins in Water

The occurrence of cyanobacterial toxins affects aquatic organisms, terrestrial animals (both wild and domestic), and humans. Detrimental effects have been documented in the scientific literature during the past 50 years. Possible guideline values of some cyanobacterial toxins (microcystins, cylindrospermopsin, and anatoxin-a) are estimated, and they show that children and infants are more susceptible to cyanobacterial toxins than adults. Therefore, particular attention should be paid when cyanobacterial blooms occur, even at relatively low cell counts, to protect children and infants from possible risks. Based on these guideline values and the occurrence of the toxins, it can be concluded that chronic and subchronic exposure to cyanobacterial toxins does occur in some populations, particularly in developing countries where high proportions of the population consume untreated surface water directly, such as pond, ditch, river, or reservoir water. Because wildlife and domestic animals consume a large amount of untreated water daily, they are at higher risk than humans from cyanobacterial toxins. Calculated guideline values in Section X show that a relatively high risk posed by the toxins to these animals is likely to occur, even at low cell densities.

Use of polynomial expressions to describe the bioconcentration of hydrophobic chemicals by fish

For the bioconcentration of hydrophobic chemicals by fish, relationships have been previously established between uptake rate constants (k1) and the octanol/water partition coefficient (Kow), and also between the clearance rate constant (k2) and Kow. These have been refined and extended on the basis of data for chlorinated hydrocarbons, and closely related compounds including polychlorinated dibenzodioxins, that covered a wider range of hydrophobicity (2.5 less than log Kow less than 9.5). This has allowed the development of new relationships between log Kow and various factors, including the bioconcentration factor (as log KB), equilibrium time (as log teq), and maximum biotic concentration (as log CB), which include extremely hydrophobic compounds previously not taken into account. The shape of the curves generated by these equations are in qualitative agreement with theoretical prediction and are described by polynomial expressions which are generally approximately linear over the more limited range of log Kow values used to develop previous relationships. The influences of factors such as hydrophobicity, aqueous solubility, molecular weight, lipid solubility, and also exposure time were considered. Decreasing lipid solubilities of extremely hydrophobic chemicals were found to result in increasing clearance rate constants, as well decreasing equilibrium times and bioconcentration factors.

Polycyclic aromatic hydrocarbons in air, soil and vegetation in the vicinity of an urban roadway

The polycyclic aromatic hydrocarbon (PAH) content of air particulate matter, surface soil and grass in the vicinity of an urban roadway was measured using gas chromatography. All fourteen PAHs analyzed for were found in soil and, except for dibenz[a,h]anthracene, were also detected in air particulate matter. Only phenanthrene, anthracene, fluoranthene and pyrene were detected in grass. Motor vehicle exhaust was the dominant source of PAHs in air particulate matter and soil. The soil concentrations of PAHs decrease with increasing distance from the road, although significant concentrations were present at a distanc of 15m. PAHs with three or four rings existed in both particulate and vapour forms in the atmosphere, which probably contributed to their relatively wide distribution. On the other hand, the PAHs with more than four rings were deposited close to the roadway due to their predominant particulate form.

Bioconcentration of lipophilic compounds by some aquatic organisms.

With nondegradable, lipophilic compounds having log P values ranging from 2 to 6, direct linear relationships have been found between the logarithms of the equilibrium bioconcentration factors, and also reciprocal clearance rate constants, with log P for daphnids and molluscs. These relationships permit calculation of the times required for equilibrium and significant bioconcentration of lipophilic chemicals. Compared with fish, these time periods are successively shorter for molluscs, then daphnids. The equilibrium biotic concentration was found to decrease with increasing chemical hydrophobicity for both molluscs and daphnids. Also, new linear relationships between the logarithm of the bioconcentration factor and log P were found for compounds not attaining equilibrium within finite exposure times.

Bioaccumulation behavior of persistent organic chemicals with aquatic organisms.

Chemicals are a vital part of everyday life. They come in the form of fuels, antibiotics, pesticides, plastic containers, agricultural fertilizers, photocopying compounds, and so on. Society cannot survive in its present form without them. Growth in the numbers of chemicals used during recent decades has been extraordinary. In 1980 the total number of substances commercially available was estimated at 40,000 with about 2000 new ones being placed on the market each year (Schmidt-Bleek and Haberland 1980).

Concentrations of persistent lipophilic compounds in fish are determined by exchange across the gills, not through the food chain

Uptake of persistent lipophilic toxicants in fish occurs via the food and by transfer across the body surface, notably the gills. Flux rates of most lipid soluble toxicants across the gills is rapid and the animal must eat at very high rates for feeding to have a significant effect on toxicant concentration in the body. The relative rates of uptake via feeding and transfer across the gills are analyzed from a theoretical and experimental standpoint. At the low feeding rates typical of fish, the uptake of toxicants in the food can be ignored when estimating toxicant body concentration.

Relationships between partition coefficient, uptake rate constant, clearance rate constant and time to equilibrium for bioaccumulation

Abstract Theoretical derivations together with published experimental data on bioaccumulation of lipophilic compounds by certain groups of fish indicates that the uptake and clearance rate constants have a fixed relationship to the octanol to water partition coefficient over the partition coefficient range 10 2.5 to 10 6 . This allows the calculation of times to establish effective equilibrium, and significant bioaccumulation of compounds in relation to the partition coefficient. By extrapolation superlipophilic compounds (partition coefficients > 10 6 ) have been shown to require a minimum period of 0.5 years increasing to 10 years when P = 10 8 to establish effective equilibrium and compounds with partition coefficients >10 13 are not bioaccumulated to any significant extent. In practice then, a direct relationship between the bioaccumulation factor and the partition coefficient will not result with superlipophilic componds.

Ambient Temperature and Cardiorespiratory Morbidity: A Systematic Review and Meta-analysis

Background: The effect of extreme temperature has become an increasing public health concern. Evaluating the impact of ambient temperature on morbidity has received less attention than its impact on mortality. Methods: We performed a systematic literature review and extracted quantitative estimates of the effects of hot temperatures on cardiorespiratory morbidity. There were too few studies on effects of cold temperatures to warrant a summary. Pooled estimates of effects of heat were calculated using a Bayesian hierarchical approach that allowed multiple results to be included from the same study, particularly results at different latitudes and with varying lagged effects. Results: Twenty-one studies were included in the final meta-analysis. The pooled results suggest an increase of 3.2% (95% posterior interval = −3.2% to 10.1%) in respiratory morbidity with 1°C increase on hot days. No apparent association was observed for cardiovascular morbidity (−0.5% [−3.0% to 2.1%]). The length of lags had inconsistent effects on the risk of respiratory and cardiovascular morbidity, whereas latitude had little effect on either. Conclusions: The effects of temperature on cardiorespiratory morbidity seemed to be smaller and more variable than previous findings related to mortality.

Risk to breeding success of fish-eating Ardeids due to persistent organic contaminants in Hong Kong: evidence from organochlorine compounds in eggs

Eggs of two Ardeid species, the Little Egret (Egretta garzetta) and the Black-crowned Night Heron (Nycticorax nycticorax), were collected from two egretries located in the New Territories of Hong Kong with one located near the internationally acclaimed wetland reserve, the Mai Po Marshes, and the other in a remote site (A Chau). The eggs were analysed for organochlorine (OC) compounds including the DDTs, PCBs, hexachlorocyclohexanes (HCHs) and the chlordanes (CHLs). All of the OCs under investigation were detected in the eggs of both species with significantly higher levels in the Little Egret (DDTs, 560-2200; PCBs, 270-1700; CHLs, 81-470 ng g(-1) wet weight) than the Night Heron (DDTs, 210-1200; PCBs, 85-600; CHLs 59-75 ng g(-1) wet weight). The DDTs consisted mainly of DDE with levels ranging from 85% to 95% of the total. The HCHs were at about the same levels in both species (8.4-30 ng g(-1) wet weight). All of the OCs had linear concentration probability distributions on a log-normal basis which were used to evaluate exposure associated with these compounds as part of a probabilistic risk analysis. A linear dose/response relationship for the percentage reduction in the survival of young associated with DDE in eggs was developed. This probabilistic relationship was used to establish the threshold level (1000 ng g(-1) wet weight) at which there was a significant level of reduction in the survival of young above zero and the variability in DDE concentrations at this effect level. Using a threshold level of 1000 ng g(-1), the calculated Risk Quotient (RQ) had a 12.4% probability of RQ exceeding unity with the Night Heron, and 40.9% with the Little Egret. These results indicate that the DDTs in eggs would be expected to be associated with adverse effects on the survival of young of both species, particularly the Little Egret.

Petroleum hydrocarbons in aquatic ecosystems — behavior and effects of sublethal concentrations: Part 2

Most research on the effects of petroleum in aquatic systems has concentrated on the immediate and short‐term toxic effects. This review collates and evaluates the results of research concerned with the effects of sublethal concentrations of petroleum hydrocarbons on aquatic organisms and to a lesser extent, ecosystems, and considers some of the implications for human health. The available information on quantities of petroleum hydrocarbons which are released into the sea as well as the concentration and types which occur in oceanic areas is presented. The various mechanisms by which hydrocarbons can enter different classes of aquatic organisms are outlined, as well as storage, metabolic, and excretion processes. This information is utilized in applying to petroleum hydrocarbons the mathematical modeling principles which have been developed during investigations of other environmentally persistent substances. In this context the behavior of petroleum hydrocarbons in food webs is considered, particularly t...