David Stone

Time to death response in carabid beetles exposed to multiple stressors along a gradient of heavy metal pollution.

We investigated the responses of invertebrates inhabiting polluted environments to multiple stressors. Carabid beetles (Pterostichus oblongopunctatus F.) were subjected to food deprivation and insecticide treatment (dimethoate) to resolve trends associated with a gradient of heavy metal pollution. Metal concentrations along the gradient of five sites ranged from approximately 150 to 10,500 mg/kg Zn, 136 to 2600 mg/kg Pb, and 0.84 to 81.9 mg/kg Cd. There was no difference in body mass along the pollution gradient. However, the beetles originating from the most contaminated sites were significantly less tolerant to food deprivation than beetles from the reference site. Median survival time was 120 h for the two most polluted sites, compared with 168 h at the reference site. Beetles from the two most polluted sites were also significantly more susceptible to dimethoate at 0.1 microgram active ingredient/beetle. Median survival times were 12 and 123 h for beetles from the two most polluted sites and 359 h for the reference site. Carabid beetles exposed to chronic pollution, therefore, exhibit elevated susceptibility to additional stressors.

Trends in detoxification enzymes and heavy metal accumulation in ground beetles (Coleoptera: Carabidae) inhabiting a gradient of pollution

Non-specfic carboxylesterase and glutathione S-transferase activity was measured in the ground beetle, Pterosthicus oblongopunctatus (Coleoptera: Carabidae), from five sites along a gradient of heavy metal pollution. A previous study determined that beetles from the two most polluted sites (site codes OLK2 and OLK3) were more susceptible to additional stressors compared with beetles from the reference site (Stone et al., Environ. Pollut. 113, 239-244 2001), suggesting the possibility of physiological impairment. Metal body burdens in ground beetles from five sites along the gradient ranged from 79 to 201 microg/g Zn, 0.174 to 8.66 microg/g Pb and 1.14 to 10.8 microg/g Cd, whereas Cu seemed to be efficiently regulated regardless of metal levels in the soil. Beetle mid- and hindguts were homogenized and the soluble fraction containing glutathione S-transferase (GST) and carboxylesterase (CaE) was assayed using kinetic analyses. Significantly higher levels of GST were found only in female beetles from the most polluted sites (OLK2 and OLK3; P=0.049, P<0.001, respectively) compared with the reference site (OLK7). In addition, OLK3 females had significantly higher levels of CaE compared with the reference beetles (P=0.01). Male beetles did not differ in enzyme activity along the metal gradient. Overall, obvious trends in detoxification enzymes were not detected in ground beetles in association with metal body burdens.

Dialkyl phosphates as biomarkers of organophosphates: The current divide between epidemiology and clinical toxicology

Context. Organophosphate insecticides are widely utilized throughout the world. The cholinergic toxidrome, resulting from cholinesterase inhibition, is the clinically relevant endpoint in organophosphate poisoning. In recent years, urinary dialkyl phosphates (DAPs) have emerged as a common method of assessing exposure to organophosphates in epidemiological investigations. Using dialkyl phosphates as biomarkers of exposure to organophosphates, several recent epidemiological studies have reported associations with adverse health outcomes. The purpose of this article is to review the application and limitations of urinary DAPs as biomarkers of exposure to organophosphate insecticides. Methods. A literature search was conducted of the PubMed database, using keywords dialkylphosphate” and “dialkyl phosphate.” The scientific literature was reviewed to identify sources of dialkyl phosphate metabolites from in vivo metabolism of organophosphates, and as environmental degradation products. Epidemiological investigations were reviewed to summarize the use of use of DAPs as biomarkers in cross-sectional studies, occupational exposures, acute poisonings, and in health outcome studies. Emphasis was placed on the assessment of DAPs in the context of existing biomarker frameworks, as defined by the National Research Council. Studies were assessed for concurrent use of cholinesterase activity as a biomarker of effect, and whether a dose-response relationship could be determined between DAPs and cholinesterase depression or cholinergic effects. Results. Over 184 publications were identified, describing dialkyl phosphates and their use as biomarkers of exposure. The in vivo metabolism of organophosphates yields different DAPs, depending upon whether they undergo bioactivation or detoxification. The detection of urinary DAPs does not provide specificity with respect to the organophosphate from which they were derived, or their toxicological potency. Several recent studies documented the common presence of DAPs in residential environments and foods. Experimental studies support that DAPs have significant oral bioavailability, and undergo little to no metabolism prior to urinary excretion. Cross-sectional studies in multiple countries confirm that urinary DAPs are commonly detectable in the general population. No occupational studies were identified supporting a dose-response relationship between DAPs and significant cholinesterase inhibition. No occupational studies were identified supporting evidence of a threshold level of DAPs excretion at which clinical cholinergic signs or symptoms have been observed. Recent prospective epidemiological studies using DAPs as biomarkers have not concurrently assessed effects on cholinesterase activity, or conducted analyses that distinguish different DAPs that reflect bioactivation versus detoxification pathways. Discussion. There are numerous limitations to the use of DAPs as biomarkers of exposure. These include a lack of specificity with respect to the organophosphate from which they were derived, and a growing body of evidence that toxicologically irrelevant DAPs are commonly encountered in food and the environment. Substantial intra- and inter-day variability has been reported for dialkyl phosphate excretion in humans, which is problematic for studies that rely on single measurements to assess exposure. The toxicological distinction between different DAPs reflecting biomarkers of activation and detoxification processes has not been considered in some prospective epidemiological studies. A relationship between DAPs as biomarkers of exposure and the critical biomarker of effect, cholinesterase activity, has not been established. Conclusions. The science of exposure assessment using DAPs as biomarkers is not advancing, and this complicates the interpretation of epidemiological studies. At the current time, DAPs have very limited utility in clinical toxicology or in the risk assessment process for organophosphates. Until these limitations are addressed, the appropriate role of DAPs in the assessment of human health risks from organophosphates is unclear.

Exposure Assessment and Risk of Gastrointestinal Illness Among Surfers

Surfing is a unique recreational activity with the possibility of elevated risk for contracting gastrointestinal (GI) illness through ingestion of contaminated water. No prior studies have assessed exposure from ingestion among surfing populations. This study estimated the magnitude and frequency of incidental water ingestion using a Web-based survey and integrated exposure distributions with enterococci distributions to predict the probability of GI illness at six Oregon beaches. The mean exposure magnitude and frequency were 170 ml of water ingested per day and 77 days spent surfing per year, respectively. The mean number of enterococci ingested ranged from approximately 11 to 86 colony-forming units (CFU) per day. Exposure-response analyses were conducted using an ingested dose model and two epidemiological models. Risk was characterized using joint probability curves (JPC). At the most contaminated beach, the annualized ingested dose model estimated a mean 9% probability of a 50% probability of GI illness, similar to the results of the first epidemiological model (mean 6% probability of a 50% probability of GI illness). The second epidemiological model predicted a 23% probability of exceeding an exposure equivalent to the U.S. Environmental Protection Agency (EPA) maximum acceptable GI illness rate (19 cases/1000 swimmers). While the annual risk of GI illness for Oregon surfers is not high, data showed that surfers ingest more water compared to swimmers and divers and need to be considered in regulatory and public health efforts, especially in more contaminated waters. Our approach to characterize risk among surfers is novel and informative to officials responsible for advisory programs. It also highlights the need for further research on microbial dose-response relationships to meet the needs of quantitative microbial risk assessments (QMRA).

Determination of parent and hydroxy PAHs in personal PM2.5 and urine samples collected during Native American fish smoking activities

A method was developed for the measurement of 19 parent PAHs (PAHs) and 34 hydroxylated PAHs (OH-PAHs) in urine and personal air samples of particulate matter less than 2.5 μm in diameter (PM₂.₅) using GC-MS and validated using NIST SRM 3672 (Organic Contaminants in Smokers Urine) and SRM 3673 (Organic Contaminants in Nonsmokers Urine). The method was used to measure PAHs and OH-PAHs in urine and personal PM₂.₅ samples collected from the operators of two different fish smoking facilities (tipi and smoke shed) burning two different wood types (alder and apple) on the Confederated Tribes of Umatilla Indian Reservation (CTUIR) while they smoked salmon. Urine samples were spiked with β-glucuronidase/arylsulfatase to hydrolyze the conjugates of OH-PAHs and the PAHs and OH-PAHs were extracted using Plexa and C18 solid phases, in series. The 34 OH-PAHs were derivatized using MTBSTFA, and the mixture was measured by GC-MS. The personal PM₂.₅ samples were extracted using pressurized liquid extraction, derivatized with MTBSTFA and analyzed by GC-MS for PAHs and OH-PAHs. Fourteen isotopically labeled surrogates were added to accurately quantify PAHs and OH-PAHs in the urine and PM₂.₅ samples and three isotopically labeled internal standards were used to calculate the recovery of the surrogates. Estimated detection limits in urine ranged from 6.0 to 181 pg/ml for OH-PAHs and from 3.0 to 90 pg/ml for PAHs, and, in PM₂.₅, they ranged from 5.2 to 155 pg/m(3) for OH-PAHs and from 2.5 to 77 pg/m(3) for PAHs. The results showed an increase in OH-PAH concentrations in urine after 6h of fish smoking and an increase in PAH concentrations in air within each smoking facility. In general, the PAH exposure in the smoke shed was higher than in the tipi and the PAH exposure from burning apple wood was higher than burning alder.

Longitudinal trends in organophosphate incidents reported to the National Pesticide Information Center, 1995–2007

BackgroundRegulatory decisions to phase-out the availability and use of common organophosphate pesticides among the general public were announced in 2000 and continued through 2004. Based on revised risk assessments, chlorpyrifos and diazinon were determined to pose unacceptable risks. To determine the impact of these decisions, organophosphate (OP) exposure incidents reported to the National Pesticide Information Center (NPIC) were analyzed for longitudinal trends.MethodsNon-occupational human exposure incidents reported to NPIC were grouped into pre- (1995–2000) and post-announcement periods (2001–2007). The number of total OP exposure incidents, as well as reports for chlorpyrifos, diazinon and malathion, were analyzed for significant differences between these two periods. The number of informational inquiries from the general public was analyzed over time as well.ResultsThe number of average annual OP-related exposure incidents reported to NPIC decreased significantly between the pre- and post-announcement periods (p < 0.001). A significant decrease in the number of chlorpyrifos and diazinon reports was observed over time (p < 0.001). No significant difference in the number of incident reports for malathion was observed (p = 0.4), which was not phased-out of residential use. Similar to exposure incidents, the number of informational inquiries received by NPIC declined over time following the phase-out announcement.ConclusionConsistent with other findings, the number of chlorpyrifos and diazinon exposure incidents reported to NPIC significantly decreased following public announcement and targeted regulatory action.

Meeting the challenge of identifying persistent pollutants at the state level

In 2007, the State of Oregon enacted legislation aimed at identifying persistent pollutants that could pose a threat to waters of the State and then reducing their discharge by means of a comprehensive pollution prevention program. This legislation defined a persistent pollutant as one that is toxic and persistent or bioaccumulative; a broad definition that required evaluation of an extensive number and variety of chemicals. The Oregon Department of Environmental Quality, in consultation with a science workgroup, implemented a 12-step process for identifying and prioritizing persistent pollutants consistent with this definition. This process is characterized by (a) maximum overall transparency in its conduct, including extensive public involvement, (b) 3 levels of objective and predefined criteria for categorization of a chemical as a persistent pollutant, (c) full disclosure of values and sources for all physicochemical data used for comparison with these criteria, and (d) clear acknowledgement when a chemical was identified as a persistent pollutant for reasons other than these criteria alone. This process was used to identify those chemicals relevant as persistent pollutants and to then prioritize them in terms of their relative ability to adversely impact waters of the state, with special emphasis on impacts to aquatic receptors. An initial list of 2130 chemicals was compiled from existing lists. Criteria for toxicity, persistence, and bioaccumulative potential were defined and then used with 2 different chemical property evaluation models (PBT Profiler and EPISuite) to produce a final list of 118 chemicals. The final list includes several legacy pollutants but also contains numerous current-use pharmaceuticals, personal care products, and pesticides, approximately half of which appear only once or not at all on lists compiled by others. Although it drew from the experience of others, assembling this list proved to be an exemplar of science in the service of policy.

Risk behaviors and self-reported illnesses among Pacific Northwest surfers.

Although surfers have high incidental exposure to marine waters, no studies have investigated if surfer risk behaviors (such as surfing during advisories, near an outfall, during a rain event, or use of personal protective equipment) increase or decrease the risk of acquiring waterborne illnesses. We used a web-based survey to assess the association between risk-based behaviors and self-reported illnesses among Pacific Northwest surfers. Commonly reported illnesses include: ear infection or discharge (38%), sore throat or a cough (28%), diarrhea (16%), fever (10.5%), and vomiting (7%). Surfing often during rain events was associated with an increased likelihood of diarrhea (OR = 2.7; 95% CI: 1.4-5.47), sore throat (OR = 1.26; 95% CI: 1.01-2.05), and ear infection (OR = 1.39; 95% CI: 1.01-2.32). Surfing during a health advisory was associated with increased likelihood of diarrhea (OR = 1.94; 95% CI: 1.03-4.64) and sore throat (OR = 2.32; 95% CI: 1.23-4.40). Other behaviors associated with increased illnesses include body surfing, surfing near an outfall, frequency of surfing, and use of ear plugs. Approximately 40% of surfers were unaware if they had surfed during an active health advisory and 29% knowingly surfed during advisories, suggesting the need to engage this population about potential harm and behaviors that may increase health risk.

Reports of metaldehyde and iron phosphate exposures in animals and characterization of suspected iron toxicosis in dogs

OBJECTIVE To describe reports of animals exposed to metaldehyde- and iron phosphate-containing molluscicides and characterize iron phosphate exposure incidents in dogs with clinical signs compatible with iron toxicosis. DESIGN 2-part retrospective case series. SAMPLE 1,500 reports of animals exposed to molluscicides containing metaldehyde (n … 1,285) or iron phosphate between 2001 and 2011 (n … 215; part 1) and a subset of 56 reports involving 61 dogs with suspected iron toxicosis (part 2). PROCEDURES In part 1, a National Pesticide Information Center database was searched to identify reported exposures to metaldehyde- and iron phosphate-containing molluscicides before, during, and after a regulatory transition affecting metaldehyde product labeling beginning in 2006. Source of the report, number of animals, clinical signs, and deaths were evaluated. In part 2, reports involving potential iron toxicosis in dogs were additionally reviewed for signalment, circumstances of exposure, and product identification. RESULTS Reports of metaldehyde exposures decreased each year between 2006 (n … 193) and 2011 (21), whereas reports of iron phosphate exposures increased between 2006 (n … 4) and 2010 (73); changes were not evaluated statistically. Animals had no clinical signs at the time of the call in 130 of 215 (60%) and 675 of 1,285 (53%) reports of iron phosphate and metaldehyde exposure, respectively. In dogs, 35 deaths were associated with metaldehyde exposure and no deaths were associated with iron phosphate exposure. CONCLUSIONS AND CLINICAL RELEVANCE Veterinary professionals should be aware of the potential for iron toxicosis following exposure to iron phosphate-containing molluscicides.

Carcinogenic risk as the basis for fish advisories: A critique

Fish advisories are important tools in public health practice and are primarily used to translate fish contaminant levels into consumption recommendations for consumers. Even when a targeted advisory is issued, it may alter broad food consumption patterns among the public, including diminishing intake of fish-based protein and polyunsaturated fatty acids. Such alterations may have both positive (e.g., reduced exposure to contaminants) and negative (e.g., loss of health benefits or cultural traditions associated with consuming fish) consequences. Currently, a fish advisory may be based on the potential for either noncarcinogenic or carcinogenic endpoints. Consumption recommendations based on a cancer outcome are likely to be highly restrictive, potentially diminishing opportunities for the recognized health benefits associated with a fish-rich diet. This possibility causes us to raise 3 arguments against using cancer risk as the basis for fish consumption advisories. First, the benefits of fish consumption are widely recognized. Second, the standard methodology to predict cancer risk is likely to overestimate actual risk, often by orders of magnitude. Third, the publics real and perceived concerns about cancer may result in unintended consequences, such as avoidance of fish altogether. As an alternative to cancer-based advisories, we suggest that future advisories incorporate a multidisciplinary public health framework focused on avoiding noncarcinogenic health outcomes and encouraging the public to consume a balanced diet rich in fish. We also suggest that decision makers need to 1) understand which elements of the advisory process are science and which are implicit or default policy, 2) consciously consider whether these policy elements are appropriate for their particular situation, and 3) if not, be willing to make and defend alternative policy choices.