The mussel bed and its multitude of inhabitants form a life community typical of our intertidal, rocky, open-coast areas. These animals are essentially immobile, are conveniently available at low tide, and have been well defined in their consumer order. Certain main members from this community were chosen with the intention that they would represent an index of heavy metal pollution for a given area under different seasonal and other variable conditions. Samples for monitoring were collected from two different sites. The first site was immediately outside the entrance to San Francisco Bay and located between Seal Rocks and Phelan Beach State Parks. This location was chosen to represent a water mass of supposed maximum pollution. The Golden Gate can be assumed to be the funnel through which flows all waters from the San Joaquin and Sacramento River drainages and from the San Francisco Bay area itself. The second site, immediately north of the Dillon Beach township, located at the juncture of Bodega and Tomales Bays, was chosen since it might represent a water mass of minimum pollution. This area is not immediately near any large urban influence, industrial activity or subject to heavy auto traffic. Therefore, at the outset it was hoped that the “immobile” consumer order within the mussel bed community would reflect the relative pollution of two supposedly different water masses.

The thesis examines aspects of the construction of methylmercury as an authoritative object of knowledge for Chisasibi, a Cree community on the James Bay coast in northern Quebec. I describe the evolution of a particular set of spheres of exchange which mediate economic relations between the Cree communities, the governments of Quebec and Canada, and state and corporate structures tied to the state. Knowledge claims about mercury can be seen as situated among claims of injury in a moral economy which is based on conflict over the James Bay hydro-electric project. The politicization and subsequent medicalization of these knowledge claims are described. Finally, I trace the emergence of particular concepts of 'normality', 'risk' and 'risk group' in medical and technocratic discourses about the effects of methylmercury on Canadian aboriginal populations.

The initial purpose of this work was to investigate the interaction of methylmercuric chloride (MMC) and X-irradiation given as a co-insult upon the rat blood-brain barrier (BBB). The indicators used to determine BBB alterations were mortality and the in vivo tissue uptake of radioactive sulfate administered as 3 5S-sodium sulfate. The results of the interaction studies indicated a neutralization of effects when MMC and X-irradiation were given together. X-irradiation as a single insult generally caused an increase in sulfate uptake by the brain regions monitored, whereas MC treatment generally resulted in decreased sulfate uptake. The neutralization patterns following co-insult treatments were somewhat varied in the different brain regions, exhibiting cancellation of effects in some cases and overriding by one insult in other eases. From the data obtained by this work and in the literature, it is hypothesized that the P-L organelle system of the perivascular glia serves as a trap for MMC, preventing MMC from reaching the neurons. The system appears to proliferate in response to increased peroxides in the body fluids, thereby increasing tolerance to larger doses of MMC.

The present study has attempted to investigate some of the more basic questions concerning the toxicity and accumulation of mercury in the purple shore crab, Hemigrapsus nudus. This rocky intertidal denizen is found in abundance along the entire Pacific coast of the United States from Sitka, Alaska, to the Gulf of California where it dominates the mid-tide pool region. Local specimens were collected just north of the Pacific Marine Stations, Dillon Beach, Marin County, California. The animal is hearty and can be kept in a state of good health for long periods of time in the laboratory with minimum care and negligible mortality. Most importantly, as a middle intertidal inhabitant, H. nudus would be among the first groups of organisms to feel the stress of environmental contamination from an industrial source located on the open coast. This, coupled with its wide distribution, indicates its possible use as an environmental monitor.

No description available.

Responses to sublethal concentrations of mercury were determined and compared for several populations of the mayfly, Isonychia bicolor from sites on two mercury polluted rivers in Virginia (USA). Results from laboratory respiration experiments indicated that small nymphs were more sensitive to mercury than larger nymphs, and that sensitivity increased with temperature. In addition, mayfly nymphs from polluted sites on the less contaminated South River were found to be more resistant to sublethal doses of inorganic mercury than nymphs from a reference site as indicated by smaller changes in respiration following exposure. Results of preexposure treatments suggested a genetic basis for the observed tolerance. No evidence of tolerance was observed in nymphs from the more contaminated Holston River. Field surveys revealed no significant differences in age structure, growth, or survival between populations at reference and polluted sites on the South River. However, growth and survival of nymphs from the polluted site on the Holston River were significantly slower than at the reference site during the summer. In fact, shortly after the summer generation hatched, nymphal density at contaminated sites declined to zero. This apparent local extinction may have been due to increased toxicity of mercury at warmer temperatures. Results of reciprocal transplant experiments conducted at sites on the South River suggested that population differences in maintenance costs observed in short-term laboratory experiments, may have been reflected by population differences in fecundity in long-term field experiments. When nymphs from the reference site on South River were transplanted and allowed to develop at a contaminated site, lower fecundities were observed than for the native population. No population differences in fecundities were observed on the Holston River. The relationship between allozyme genotype to survival of I. bicolor nymphs to acute mercury exposure was also tested. The probability of survival and individual times to death (TTD) were found to be significantly different among genotypes at the Glucose Phosphate Isomerase (GPI) locus. This was true at both summer and winter temperatures and for populations from two separate, unpolluted streams. However, genotypes identified as sensitive and tolerant in these experiments showed no consistent relationship with environmental mercury levels in polluted rivers. Therefore, the use of allozyme variants as a biomarker to assess evolutionary change in populations due to mercury pollution may be impractical in freshwater systems. / Ph. D.

Splenic and lymph node lymphocytes from Balb/C mice were activated in vitro by the heavy metal cations, Zn⁺⁺ and Hg⁺⁺, as noted by the several-fold increases in ³H-thymidine incorporation at 144 hours of culture. Optimal mitogenic concentrations of Zn⁺⁺ and Hg⁺⁺ were 200 μM and 10 μM, respectively. Data from experiments in which three different methods were used to enrich for either T or B splenic lymphocytes, i.e. cell passage over nylon wool columns, use of athymic Nu/Nu mouse spleen cells, or cell lysis with monoclonal anti-Thy-1 antibody plus complement, suggested that Zn⁺⁺ and Hg⁺⁺ were mitogens for T cells. Removal of macrophages from spleen cells by treatment with carbonyl iron followed by cell passage through nylon wool eliminated the lymphocyte responses to Zn⁺⁺ and to Hg⁺⁺. Moreover, addition of these macrophage-depleted lymphocytes to monolayers of resident peritoneal macrophages restored the lymphocyte responses to these mitogens. Both Zn⁺⁺ and Hg⁺⁺ activated splenic lymphocytes to display lectin-dependent cytotoxicity and to produce gamma interferon. Furthermore, Zn⁺⁺ induced low levels of natural killer activity in spleen cells. In contrast to spleen and lymph node cells, thymocytes and bone marrow lymphocytes did not respond to either cation under standard culture conditions. However, when cultured in the presence of E. coli-derived lipopolysaccharide (LPS) and 2-mercaptoethanol for 144 hours, thymocytes were activated by Zn⁺⁺ (200 μM) but not by Hg⁺⁺. Quantities of LPS as low as 1.0 ng/ml satisfied this culture requirement. Purified interleukin 1 could not replace the helping activity mediated by LPS. Thymocyte subpopulation studies showed that Zn⁺⁺ activated enriched peanut lectin receptor-negative mature thymocytes, but LPS was required for the response. Spleen cells from mice, intraperitoneally injected with ZnCl₂ for 7 to 14 days, were not activated in vivo as assessed by ³H-thymidine incorporation in vitro, nor did they display enhanced responses to T-cell or B-cell mitogens. However, zinc administration had negative effects by decreasing spleen cell numbers by 31% and thymic weight by 59%. A theoretical model is presented in which Zn⁺⁺ and Hg⁺⁺ may mediate their stimulating effects in vitro by altering histocompatibility "self" structures on the surface of lymphocytes and macrophages via interactions with sulfhydryl groups on these structures to which T lymphocytes with receptors for "altered self" structures respond with proliferation or cytotoxicity.

Content removed due to copyright restriction: Jones, L. M. (2004). Focus on fillings: A qualitative health study of people medically diagnosed with mercury poisoning, linked to dental amalgam. Acta Neuropsychiatrica, 16(3), 142-148. Jones, L. (1999). Dental amalgam and health experience: Exploring health outcomes and issues for people medically diagnosed with mercury poisoning. The Bulletin, 97, 29-33. / The longstanding debate over the safety of mercury in dentistry has latterly moved from scientific argument to public health dilemma. Mercury is a neurotoxin. Adverse psychological outcomes can result from exposure, so The Quicksilver Quest aimed to investigate mercury in dentistry from a qualitative, critical health psychology perspective, and a quantitative, neuropsychology assessment. The qualitative study used focus group methodology to explore micro-mercurialism linked to dental amalgam fillings. A random sample of people, who had been medically diagnosed with mercury poisoning, formed seven focus groups. The discussion of experiences, beliefs, and health was analysed for themes and issues. The main findings were that the participants were not a homogeneous group, as had been anticipated, but fell into categories differentiated by their symptoms, fiscal resources, and motivation. A placebo effect was rejected as an exclusive explanation for the positive health outcomes reported by those who had had amalgam removal and detoxification. The quantitative study investigated the long-term effects of occupational mercury exposure on a cohort of women in dentistry. The aim was to test the null hypothesis: that women who endured high occupational mercury exposure in the 1970s (43 participants), and matched controls (32 participants), would show no between-group differences on a general and reproductive health survey, and a nine-test neurobehavioural assessment. Results generally supported accepting the null hypothesis. Significant exceptions were current symptom experience, reproductive health, and two mood subscales. There was a suggestion of peripheral nerve damage in the exposed group. Overall, the general discussion systematically reviews tension points in the debate, in light of a proposed model of tolerance to mercury. This begins to explain how it might appear that mercury in dentistry is safe for dental personnel, as pro-amalgam debaters claim, yet unsafe for some dental patients, as anti-amalgam debaters claim. Further study is suggested for occupationally exposed women, on tremor, and to test the proposed tolerance to mercury model. Finally, as the debate has a political aspect, a recommendation is made for a shift in public health policy to dental amalgam being restricted to use only in an adult population.

Tissue samples from spotted gar (Lepisosteus oculatus) and largemouth bass (Micropterus salmoides) were collected from Caddo Lake. Gar and bass livers were subjected to histological investigation and color analysis. Liver color (as abs at 400 nm) was significantly correlated with total mercury in the liver (r2 = 0.57, p = 0.02) and muscle (r2 = 0.58, p = 0.01) of gar. Evidence of liver damage as lipofuscin and discoloration was found in both species but only correlated with liver mercury concentration in spotted gar. Inorganic mercury was the predominant form in gar livers. In order to determine the role of mercury speciation in fish liver damage, a laboratory feeding study was employed. Zebrafish (Danio rerio) were fed either a control (0.12 ± 0.002 µg Hg.g-1 dry wt), inorganic mercury (5.03 ± 0.309 µg Hg.g-1 dry wt), or methylmercury (4.11 ± 0.146 µg Hg.g-1 dry wt) diet. After 78 days of feeding, total mercury was highest in the carcass of zebrafish fed methylmercury (12.49 ± 0.369 µg Hg.g-1 dry wt), intermediate in those fed inorganic mercury (1.09 ± 0.117 µg Hg.g-1 dry wt), and lowest in fish fed the control diet (0.48 ± 0.038 µg Hg.g-1 dry wt). Total mercury was highest in the viscera of methylmercury fed zebrafish (11.6 ± 1.86 µg Hg.g-1 dry wt), intermediate in those fed inorganic diets (4.3 ± 1.08 µg Hg.g-1 dry wt), and lowest in the control fish (below limit of detection). Total mercury was negatively associated with fish length and weight in methylmercury fed fish. Condition factor was not associated with total mercury and might not be the best measure of fitness for these fish. No liver pathologies were observed in zebrafish from any treatment.

Indiana University-Purdue University Indianapolis (IUPUI) / Mercury (Hg) has proven to be a risk to the public, mainly through the consumption of fish. Because of this, many fish consumption advisories have been issued in Indiana. Although much is known about the global cycle of mercury, little is known about how local and regional emission sources of mercury impact local and regional mercury cycling. This study’s objective was to determine the scope of mercury concentration in central Indiana by using a broad grid of soil mercury measurements. Sampling was designed to capture the net retained mercury content in soils, and to determine whether spatial patterns in exist in soil mercury contents that could be related to emission sources of mercury and post-emission transport patterns from wind. Results from this study revealed significant differences in mercury concentrations for soils in central Indiana. The core of the study area, concentrated in the urban area of Indianapolis, exhibited soil mercury contents that were 20 times higher than values in the outskirts of the study area. The spatial pattern resembled a bulls-eye shape centered on Indianapolis, and with comparison to the reported Hg emission from local sources, including a coal-fired power plant, indicates a strong regional deposition signal linked to those emission sources but marked by wind-driven transport to the northeast. This effect of local emission sources resulting in local deposition indicates that limiting mercury emissions will have a net beneficial impact on local environmental quality and human health.