Assessment of persistent organic pollutants in killer whales (Orcinus orca) of the Canadian Arctic: Implications for subsistence consumption and conservation strategies.

Killer whales (Orcinus orca) historically restricted to certain Arctic regions due to extensive sea ice have recently been documented farther north and for longer durations in the Canadian Arctic. These apex predators accumulate high levels of persistent organic pollutants (POPs). The objective of this study was to evaluate the concentrations and profiles of POPs in killer whales of the Canadian Arctic, thus determining potential risks for Inuit communities if consumed. Biopsies were collected from 33 killer whales across areas of the Canadian Arctic between 2009 and 2021. Significant variability in POP concentrations was observed among whales. The cumulative POP concentrations ranged from 12 to >2270 mg/kg lw, representing ∼200-fold increase from the least to the most contaminated individual. The rank order of concentrations of the top five contaminant classes was ∑DDT, ∑PCB, ∑CHL, ∑Toxaphene, and Dieldrin. Several emerging Arctic contaminants were detected, including chlorpyrifos, endosulfan, pentachloroanisole, and polychlorinated naphthalenes, although at relatively lower concentrations than legacy POPs. Considering the elevated blubber POP levels in killer whales, recommended daily consumption thresholds, established based on human tolerable daily intake (TDI) values, were notably restricted for ∑PCB (<0.14 g), ∑DDT (<6.9 g), ∑CHL (<13 g), dieldrin (<8 g) and heptachlor epoxide (<5 g). Killer whales in the Canadian Arctic exhibited higher POP concentrations than other commonly hunted species such as polar bears, ringed seals, and Arctic char. We acknowledge that a more holistic risk assessment of diet is required to assess the cumulative impacts of contaminant mixtures as well as nutritional quality of tissues commonly consumed by northern communities.

Fitness costs associated with a GABA receptor mutation conferring dieldrin resistance in Aedes albopictus.

Understanding the dynamics of insecticide resistance genes in mosquito populations is pivotal for a sustainable use of insecticides. Dieldrin resistance in Aedes albopictus is conferred by the alanine to serine substitution (A302S or RdlR allele) in the γ-aminobutyric acid (GABA) receptor encoded by the Rdl gene. On Reunion Island, dieldrin resistance was initially reported in natural Ae. albopictus populations sampled in 2008 despite the ban of dieldrin since 1994. To monitor insecticide resistance in Ae. albopictus on the island and to identify its drivers, we measured (i) the frequency of resistance alleles in 19 distinct natural populations collected between 2016 and 2017, (ii) fitness costs associated with dieldrin resistance in laboratory-controlled experiments, and (iii) the resistance conferred by RdlR to fipronil, an insecticide widely used on the island and reported to cross-react with RdlR. The results show a persistence of RdlR in Ae. albopictus natural populations at low frequencies. Among the measured life history traits, mortality in pre-imaginal stages, adults' survival as well as the proportion of egg-laying females were significantly affected in resistant mosquitoes. Finally, bioassays revealed resistance of RdlR mosquitoes to fipronil, suggesting that the use of fipronil in natura could select for the RdlR allele. This study shows that dieldrin resistance is persistent in natural mosquito populations likely as a result of combined effects between fitness costs associated with RdlR and selection exerted by cross-reacting environmental insecticides such as fipronil.

Iron turning waste: Low cost and sustainable permeable reactive barrier media for remediating dieldrin, endrin, DDT and lindane in groundwater.

The feasibility and effectiveness of iron turning waste as low cost and sustainable permeable reactive barrier (PRB) media for remediating dieldrin, endrin, dichlorodiphenyltrichloroethane (DDT), and lindane individually (batch system) and combined (continuous flow column) in water were investigated. After 10 min of reaction in a batch system, removal of endrin, dieldrin, and DDT was higher (86-91 %) than lindane (41 %) using 1 g of iron turning waste in 200 mL of pesticide solution (20 µg/L for each pesticide). Among the studied pesticides, only lindane removal decreased substantially in the presence of nitrate (37 %) and magnesium (18 %). Acidic water environment (pH = 4) favored the pesticide removal than neutral and basic environments. For the column experiments, sand alone as PRB media was ineffective for remediating the pesticides in water. When only iron turning was used, the removal efficiencies of lindane, endrin, and dieldrin were 83-88 % and remained stable during 60 min of the experiments. DDT removal was less than other pesticides (58 %). Sandwiching the iron turning waste media between two sand layers improved DDT removal (79 %) as well as limited the iron content below a permissible level in product water. In a long-term PRB column performance evaluation, iron turning waste (150 g) removed all pesticides in water (initial concentration of each pesticide = 2 µg/L) effectively (≥94 %) at a hydraulic retention time of 1.6 h. Iron turning waste, which was mainly in the form of zerovalent iron (Fe0), was oxidized to ferrous (Fe2+) and ferric (Fe3+) iron during its reaction with pesticides, and electrons donated by Fe0 and Fe2+ were responsible for complete dechlorination of all the pesticides. Therefore, it can be used as inexpensive and sustainable PRB media for groundwater remediation especially in developing countries where groundwater contamination with pesticides is more prevalent.

Comprehensive assessment of unutilized and obsolete pesticides impact on genetic status and health of population of Almaty region.

The group of persistent organic pollutants (POPs) are particularly dangerous for the environment and by consequence for human health because of the risk to be transmitted in the food chain. Among them, the urgent problem of obsolete and forbidden organochlorinated pesticides (OCPs) needs a rigorous management in many countries, including Kazakhstan. The aim of our study was to evaluate the effect of pesticides content in food products on the genetic status and health of the population living on the contaminated areas near destroyed warehouses for OCPs (4 villages of Talgar district and 1 control site, Almaty region). The food products sampled in Taukaraturyk (control site), and in 4 villages where non-utilized obsolete pesticides were discovered: Beskainar, Kyzylkairat, Amangeldy, and Belbulak. The contents of 24 pesticides in food products from plant (apples, pears, tomatoes, cucumbers, sweet peppers) and animal (beef meat, cow milk, honey) origin, that grown in places of localization of non-utilized OCPs, were determined, sometimes in high and unacceptably high concentrations (before 2500 times over MRL). In pears, the pesticides content (especially DDT, γ-HCH, ß-HCH, endosulfan, and aldrin pesticide group), was higher than in other fruits. Among vegetables, the highest levels of all groups of pesticide were found in cucumbers. Beef meat samples demonstrated increased contents of ß-HCH, γ-HCH, endrin and dieldrin. In cow milk samples only the high concentration of dieldrin was found. The content of pesticides in meat was 4-5 times higher than in milk. The medical examinations, carried out among the cohorts living around the polluted by pesticides territories and control cohort from ecologically favorable village, showed that there were more individuals with high and middle levels of somatic health in the control group than in groups exposed to OCPs. The long-term effect of the pesticide contamination of the environment on genetic status of the population was assessed by chromosomal aberration (CA) frequencies. The highest level of chromosomal aberrations was identified for the examined residents of Kyzylkairat (41%) and Belbulak (38%), a high level in Amangeldy (12%), and middle level in Beskainar (6.5%). The association between the CA frequency, health status and the pesticides contents in food were assessed by a Spearman rank correlation. The low indicators of somatic health status were strictly associated with high levels of CA, and good health status indicates that the CA rates did not exceed the spontaneous level of mutagenesis. The strongest correlation was shown between high levels of chromosomal aberrations and the content of different pesticides in pears (Cr = 0.979-0.467), tomatoes (Cr = 0.877-0.476), cucumbers (Cr = 0.975-0.553) and meat (Cr = 0.839-0.368). The obtained results highlight the need to improve health protection by increasing the public awareness to the security of the storage of obsolete OCPs in order to strengthen food safety by efficient control services.

First report on probabilistic risk assessment of pesticide residues in a riverine ecosystem in South-South Nigeria.

The present study evaluated the ecological and human health risk associated with concentrations of legacy organochlorine pesticide residues in Ikpoba River, a major River in the heart of Benin City, a Nigerian urban town located in Edo State. Standard methods were used to collect, extract and analyze samples, while risk assessment was carried out using standard models and indices. Results showed varying pesticide concentrations in both sediment and water samples with α-HCH (0.24 ±â€¯0.11 µg L-l), predominant in water, whereas dieldrin (0.99 ±â€¯0.33 µg kg-l) was the highest concentration in sediment. Compared to the Sediment Quality Guidelines (SQGs), this study concentrations of pesticides in sediments were below the values of effect range medium, effect range low, probable effect level and threshold effects level, suggesting low environmental hazard to benthic organisms. However, on exposure to contaminated sediments, probabilistic ecological risk assessment using Monte Carlo techniques showed potential risk to algae, daphnid and fish. Human health risk estimates using dermal and ingestion exposure deterministic and probabilistic routes revealed a potential risk to adults and children exposed to contaminated water and sediment. Estimates for detected pesticides exceeded the threshold level, indicating potential cancer effects for both children and adults who rely on the resources of the river. This study highlights the need for concerted efforts to curb the threat of pesticides and other contaminants in the aquatic environment by all relevant stakeholders in Nigeria and Africa as a whole.

Dietary exposure and risk assessment of organochlorine pesticide residues in rural communities living within catchment areas of iSimangaliso World Heritage Site, South Africa.

Dietary intake of contaminated food is a major route of human exposure to organochlorine pesticides (OCPs). Despite the prevalence of OCP usage in southern Africa for several decades, their impact on socioeconomically vulnerable communities remains largely overlooked. We investigated the accumulation of OCPs in crops commonly cultivated by rural communities surrounding iSimangaliso Wetland Park, South Africa. All samples analysed were found to be contaminated, with total OCP concentrations ranging between 190 and 240 ng g-1 ww. Elevated levels of OCP residues were detected in all products, with the majority of samples exceeding European Commission's maximum residue limits (MRLs). We combine these results with local OCP fish tissue estimates to assess potential dietary risks. Cumulative risk assessment indicated potential non-cancer risks associated with heptachlor epoxide, while a cancer risk as high as 1 in 10 was found to be associated with aldrin and dieldrin. This far exceeds USEPA guidelines and indicates that OCP residues in crops and fish from the study area pose a high risk to human health. The results of this study call for further attention to be given to the health implications of continued OCP use not only within the study area but also in Southern Africa in general.

Pesticide exposure in the local community of Vehari District in Pakistan: An assessment of knowledge and residues in human blood.

The present study is based on cross-sectional data collected from rural and market areas of Vehari District in Pakistan to assess public awareness of pesticide risks and determine the levels of exposure to organochlorine pesticides (OCPs) in the local community. Blood samples were collected from 56 volunteer donors (VDs) including children, female workers, farm workers involved in pesticide business, farm workers involved in pesticide spraying activities, and people who were living away from agricultural fields. Blood analysis showed that VDs who were involved in spraying activities had significantly higher levels of OCP residues in their blood samples than VDs from the other groups, with mean concentrations of 1.13, 0.92, 0.68 and 1.96ngmL-1 for pp-DDT, aldrin, dieldrin, and endosulfan, respectively. However, VDs who were living away from agricultural fields had significantly lower levels of pesticide residues in their blood samples, with mean concentrations of 0.30, 0.19, 0.14 and 0.41ngmL-1 for pp-DDT, aldrin, dieldrin, and endosulfan, respectively. A survey of 179 volunteer respondents (VRs) showed that a significant proportion of the VRs had little knowledge of using the recommended amounts of pesticides (65.9%). Furthermore, the majority of the VRs was found using limited protective measures during pesticide use (62.6%) and was practising unsafe storage of pesticides (87.7%). In addition, most farm workers (88.8%) reported an increasing trend in pesticide use in their farms each year. Knowledge of pesticide risks on human health increased with formal education and training. Poor knowledge regarding pesticide risks and handling among inhabitants of Vehari District contribute to high exposure levels to OCPs, particularly among farm workers. Findings are useful for policy formulation aimed at reduction of pesticide exposure in Pakistan.

Pesticides in persimmons, jujubes and soil from China: Residue levels, risk assessment and relationship between fruits and soils.

Extreme and uncontrolled usage of pesticides produces a number of problems for vegetation and human health. In this study, the existence of organophosphates (OPs), organochlorines (OCs), pyrethroids (PYs) and fungicides (FUs) were investigated in persimmons/jujubes and their planted soils, which were collected from China. One OP (dimethoate), three OCs (DDT, quintozene and aldrin), six PYs (bifenthrin, fenpropathrin, cyhalothrin, cypermethrin, fenvalerate and deltamethrin) and two FUs (triadimefon and buprofezin) were found in 36.4% of persimmons and 70.8% of jujubes, with concentrations from 1.0 µg/kg to 2945.0 µg/kg. The most frequently detected pesticides in the two fruits were fenpropathrin in persimmons and cypermethrin in jujubes, with the detection frequencies of 30.0% and 22.7%, respectively. The residues of 4.5% (persimmon) and 25.0% (jujube) of samples were higher than the maximum residue limits (MRLs) of China. Compared with the fruits, more types of pesticides and higher residues were observed in their planted soils. The most frequently detected pesticides were HCH in persimmon soil and DDT in jujube soil, with the detection frequencies of 10.9% and 12.7%, respectively. For the tested samples, 39.1% of fruit samples and 63.0% of soil samples with multiple residues (containing more than two pesticides) were noted, even up to 8 residues in fruits and 14 residues in soils. Except for cyhalothrin, the other short-term risks for the tested pesticides in the fruits were below 10%, and the highest long-term risk was 14.13% for aldrin and dieldrin. There was no significant health risk for consumers via consumption of the two fruits.

Distribution and health risk assessment of organochlorine pesticides (OCPs) residue in edible cattle tissues from northeastern part of Egypt: High accumulation level of OCPs in tongue.

Food consumption is an important route of human exposure to organochlorine pesticides (OCPs). In order to assess the potential human health risks associated with OCPs, edible cattle tissues (liver, kidney and tongue) were collected from three slaughter houses in Mansoura, Zagazig and Ismailia cities, Egypt. Levels of 22 OCPs such as hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), aldrin, dieldrin and endrin (Drins), chlordanes (CHLs), heptachlors (HPTs) and hexachlorobenzene (HCB) residues were investigated. Among the investigated OCPs, HCHs represented the most dominant group with high proportions of γ-HCH isomer (53-91% of total HCHs). Mansoura city had the highest OCPs contamination load ranged from 0.1 to 2827 ng g(-1) lw (lipid weight). Surprisingly, tongue samples collected from Mansoura showed the highest concentration of HCHs (448 ng g(-1) lw) in comparison to liver (152 ng g(-1) lw) and kidney (266 ng g(-1) lw). Generally, contamination pattern of OCPs was in the order of HCHs > Drins > CHLs > DDTs ≅ HCB and HPTs. Estimated daily intakes (EDIs) through dietary consumption of cattle tissues were lower than the recommended acceptable daily intakes (ADIs) established by FAO/WHO. However, the hazard ratios (HRs) based on cancer risk were greater than 1.0 for HCHs based on the average and 95th centile concentrations, indicating carcinogenic effects to consumers through cattle tissues consumption.

Distribution and risk assessment of suspected endocrine-disrupting pesticides in creek water of Mumbai, India.

The present study deals with the investigation of existing pollution levels and potential ecological risk assessment of endocrine-disrupting organochlorine and organophosphorous pesticide residues in the Vasai Creek water near Mumbai. The average concentration of α- and ß-endosulfan (137.75 ng·L(-1)) exceeds the chronic criteria level of α- and ß-endosulfan (6.5 ng·L(-1)) set by US EPA for freshwater aquatic organisms. The concentration levels of aldrin (75.31 ng·L(-1)), dieldrin (71.19 ng·L(-1)) and endrin (76.60 ng·L(-1)) was found to exceed the respective criteria levels of <0.13, 65.1, and 61 ng·L(-1) as set by US EPA for protection of freshwater aquatic organisms. In addition, the level of chlorpyrifos (208.77 ng·L(-1)) exceeds the recommended concentration value of <35 ng·L(-1) set by Ministry of Environment of British Colombia. The results of our study give an indication of probable ecotoxicological risk to the marine breeding organisms of creek.

Risk assessment of agricultural pesticides in water, sediment, and fish from Owan River, Edo State, Nigeria.

The distribution of pesticides in water, sediments, Clarias gariepinus, and Tilapia zilli from the Owan River was investigated to evaluate the pollution status and potential hazard in the river system. A total of 16 pesticides were analyzed using gas chromatography (GC) equipped with electron capture detector (ECD). The concentration of pesticide residues ranged from ND to 0.43 µg/l for water samples, 0.82 to 2.14 µg/kg/dw for sediment, 0.04 to 2.34 µg/kg/ww for C. gariepinus, and 0.02 to 1.73 µg/kg/ww for T. zilli. High concentrations of organochlorine pesticides, specifically benzenehexachloride (α-BHC, γ-BHC, and ß-BHC) observed in all environmental media, are an indication of the current illegal use of banned pesticides for agricultural activities in the region. Analysis of data showed a strong correlation (r (2) = 0.7) between total organic carbon (TOC) and total pesticide residues in sediment samples. Meanwhile, risk quotient estimates for heptachlor epoxide, dieldrin, endrin, dichlorodiphenyltrichloroethane (4,4'-DDT), endosulfan I, endosulfan II, endosulfan aldehyde, and phosphomethylglycine showed potential risk to aquatic organism under observed mean concentrations (risk quotient (RQ) ≥ 1). Estimated average daily intake (EADI) for organochlorine pesticides (γ-BHC, heptachlor epoxide, aldrin, dieldrin, and endrin) was above their respective acceptable average daily intake (ADI), while hazard quotient for each of these pesticides was above the unity value (1). This indicates that there is a potential cancer risk for the local residents with life time consumption of pesticide-contaminated fish.

Comparison of plate reader-based methods with fluorescence microscopy for measurements of intracellular calcium levels for the assessment of in vitro neurotoxicity.

The intracellular calcium concentration ([Ca(2+)]i) is an important readout for in vitro neurotoxicity since calcium is critically involved in many essential neurobiological processes, including neurotransmission, neurodegeneration and neurodevelopment. [Ca(2+)]i is often measured with considerable throughput at the level of cell populations with plate reader-based assays or with lower throughput at the level of individual cells with fluorescence microscopy. However, these methodologies yield different quantitative and qualitative results. In recent years, we demonstrated that the resolution and sensitivity of fluorescence microscopy is superior compared to plate reader-based assays. However, it is currently unclear if the use of plate reader-based assays results in more 'false negatives' or 'false positives' in neurotoxicity screening studies. In the present study, we therefore compared a plate reader-based assay with fluorescence microscopy using a small test set of environmental pollutants consisting of dieldrin, lindane, polychlorinated biphenyl 53 (PCB53) and tetrabromobisphenol-A (TBBPA). Using single-cell fluorescence microscopy, we demonstrate that all test chemicals reduce the depolarization-evoked increase in [Ca(2+)]i, whereas lindane, PCB53 and TBBPA also increase basal [Ca(2+)]i, though via different mechanisms. Importantly, none of these effects were confirmed with the plate reader-based assay. We therefore conclude that standard plate reader-based methods are not sufficiently sensitive and reliable to measure the highly dynamic and transient changes in [Ca(2+)]i that occur during chemical exposure.

Polychlorinated biphenyls and organochlorine pesticides in local waterbird eggs from Hong Kong: risk assessment to local waterbirds.

The contamination status of the marine environment in Hong Kong was studied by measuring concentrations of organochlorine (OC) pollutants (i.e., hexachlorobenzene, aldrin, dieldrin, endrin, mirex, total heptachlor, total chlordane, total DDTs, total PCBs, and total toxaphenes) in the eggs of selected waterbird species from different locations around the city: Little Egret (Egretta garzetta) and Chinese Pond Heron (Ardeola bacchus) from Mai Po Village, Great Egret (Ardea alba) and Black-crowned Night Heron (Nycticorax nycticorax) from A Chau, and Chinese Pond Heron (A. bacchus) from Ho Sheung Heung. The mean concentrations of total PCBs and total DDTs ranged from 191-11,100 ng g(-1) lipid and 453-49,000 ng g(-1) lipid, respectively. Recent exposure of waterbirds to technical chlordane was found in Hong Kong. The risk characterization demonstrated potential risks to birds associated with exposure to DDE, which was found to cause a reduction in survival of young in Hong Kong Ardeids based on the endpoint in the risk assessment.

A whole sample toxicity assessment to evaluate the sub-lethal toxicity of water and sediment elutriates from a lake exposed to diffuse pollution.

The impact of diffuse pollution in aquatic systems is of great concern due to the difficult to measure and regulate it. As part of an ecological risk assessment (ERA), this study aims to use a whole sample toxicity assessment to evaluate the toxicity of water and sediment from Lake Vela, a lake that has been exposed to diffuse pollution. In this way, standard (algae: Pseudokirchneriella subcapitata; cladoceran: Daphnia magna) and local species (algae: Aphanizomenon flos-aquae; cladoceran: Daphnia longispina) were exposed to surface water, and sediment elutriates were collected seasonally from two sites at Lake Vela: one near the east bank (ES), surrounded by agricultural lands; and the other near the west bank (WS), surrounded by a forest. The results confirmed the seasonal contamination of both environmental compartments by pesticides, including organochlorine pesticides, and the presence of high concentrations of nutrients. Although both sites were contaminated, higher levels of pesticides and nutrients were detected in ES, particularly in the sediments. Bioassays showed that water samples (100% concentration) collected in summer and autumn significantly affected the growth rate of P. subcapitata, which could be attributed to the presence of pesticides. Likewise, they revealed an apparent toxicity of elutriates for P. subcapitata and for both daphnids, in summer and autumn. In fact, although pesticides were not detected in elutriates, high levels of un-ionized ammonia were recorded, which is considered highly toxic to aquatic life. By comparing the several species, P. subcapitata was revealed to be the most sensitive one, followed by the daphnids, and then by A. flos-aquae. Results obtained in this study underlined the importance of whole samples toxicity assessment for characterizing the ecological effects of complex mixtures from diffuse inputs, in the ERA processes.

Global assessment of organic contaminants in farmed salmon.

The annual global production of farmed salmon has increased by a factor of 40 during the past two decades. Salmon from farms in northern Europe, North America, and Chile are now available widely year-round at relatively low prices. Salmon farms have been criticized for their ecological effects, but the potential human health risks of farmed salmon consumption have not been examined rigorously. Having analyzed over 2 metric tons of farmed and wild salmon from around the world for organochlorine contaminants, we show that concentrations of these contaminants are significantly higher in farmed salmon than in wild. European-raised salmon have significantly greater contaminant loads than those raised in North and South America, indicating the need for further investigation into the sources of contamination. Risk analysis indicates that consumption of farmed Atlantic salmon may pose health risks that detract from the beneficial effects of fish consumption.

Mecanismos de acción de xenobióticos en ovocitos de anfibios / Xenobiotic mechanisms of action in amphibian oocytes

Comprender los procesos que determinan la toxicidad de diversas sustancias a nivel celular constituye un desafío para el desarrollo tecnológico actual. Los ovocitos de diversas especies son utilizados con distintos propósitos en investigación. El tamaño de los ovocitos de anfibios y la facilidad con que puede obtenerse un gran número de ellos como células aisladas, hacen de los mismos el sistema de elección para múltiples propósitos, tales como: estudios de las etapas tempranas de la reproducción, técnicas de fertilización in vitro, expresión y caracterización de receptores de membranas plasmática, mecanismos de acción de agonistas, vías metabólicas, etc. El objetivo del presente trabajo con ovocitos de sapo Bufo arenarum es estudiar los mecanismos de acción de sustancias xenobióticas a nivel bioquímico y molecular, en relación con la capacidad de éstas gametas de ser fertilizadas y avanzar a través de los estadios tempranos del desarrollo embrionario. Se ha trabajado con diversos biomarcadores que permitieron reconocer los mecanismos de toxicidad de compuestos organoclorados y más recientemente de algunos metales pesados. Se demostró que la activación de una fosfolipasa C específica por el Dieldrin provoca depleción de mediadores lipídicos y como consecuencia inhibición de la fertilización (desarrollo hasta 4-8 células). Actualmente se estudian los efectos del Zn sobre la fertilización y su probable relación con alteraciones en la actividad de enzimas de la vía de las pentosas, directamente ligada a los mecanismos de detoxificación en presencia de stress oxidativo. El estudio de los mecanismos de citotoxicidad de diversas sustancias resulta de gran utilidad cuando se lleva a cabo en gametas, porque permite también evaluar los efectos de dichas sustancias sobre la reproducción de la especie. Los ovocitos de anfibios son además células de gran interés, por su utilidad en el estudio de la citotoxicidad de una amplia variedad de contaminantes hídricos

Aldrin and dieldrin: a review of research on their production, environmental deposition and fate, bioaccumulation, toxicology, and epidemiology in the United States.

In the last decade four international agreements have focused on a group of chemical substances known as persistent organic pollutants (POPs). Global agreement on the reduction and eventual elimination of these substances by banning their production and trade is a long-term goal. Negotiations for these agreements have focused on the need to correlate data from scientists working on soil and water sampling and air pollution monitoring. Toxicologists and epidemiologists have focused on wildlife and human health effects and understanding patterns of disease requires better access to these data. In the last 20 years, substantial databases have been created and now are becoming available on the Internet. This review is a detailed examination of 2 of the 12 POPs, aldrin and dieldrin, and how scientific groups identify and measure their effects. It draws on research findings from a variety of environmental monitoring networks in the United States. An overview of the ecologic and health effects of aldrin and dieldrin provides examples of how to streamline some of the programs and improve access to mutually useful scientific data. The research groups are located in many government departments, universities, and private organizations. Identifying databases can provide an "information accelerator" useful to a larger audience and can help build better plant and animal research models across scientific fields.

Gap junctional intercellular communication is not a major mediator in the bystander effect in photodynamic treatment of MDCK II cells.

Photodynamic treatment (PDT) of confluent MDCK II cells resulted in a noticeable clustering of dead cells, consistent with a significant bystander effect. Likewise, PDT of cells in microcolonies resulted in an overabundance of microcolonies that had responded to the treatment as a single unit, that is, in which either all or no cells were dead. Confluent MDCK II cells appeared to communicate via gap junction channels, while cells in microcolonies did not. Monte Carlo simulation models were fitted to the distributions of dead cells in confluent monolayers and in microcolonies. The simulations showed that the degree of the bystander effect was higher in microcolonies than in confluent cells, suggesting that gap junction communication may be involved in the bystander effect. However, when the gap junction hypothesis was tested by treatment of microcolonies with 30 microM dieldrin, an inhibitor of gap junctional intercellular communication, there was no reduction of the bystander effect, indicating that this effect was not mediated by gap junctional intercellular communication. PDT influenced phosphorylation of tyrosine residues in several proteins in the cells. Protein phosphorylation is important in cellular signaling pathways and may be involved in the bystander effect, for example by influencing the mode of cell death.