Abstract
We present a spectroscopic analysis of Eridanus IV (Eri IV) and Centaurus I (Cen I), two ultrafaint dwarf galaxies of the Milky Way. Using IMACS/Magellan spectroscopy, we identify 28 member ...stars of Eri IV and 34 member stars of Cen I. For Eri IV, we measure a systemic velocity of
v
sys
=
−
31.5
−
1.2
+
1.3
km
s
−
1
, and velocity dispersion
σ
v
=
6.1
−
0.9
+
1.2
km
s
−
1
. Additionally, we measure the metallicities of 16 member stars of Eri IV. We find a metallicity of
Fe
/
H
=
−
2.87
−
0.07
+
0.08
, and resolve a dispersion of
σ
Fe/H
=0.20 ± 0.09. The mean metallicity is marginally lower than all other known ultrafaint dwarf galaxies, making it one of the most metal-poor galaxies discovered thus far. Eri IV also has a somewhat unusual right-skewed metallicity distribution. For Cen I, we find a velocity
v
sys
= 44.9 ± 0.8 km s
−1
, and velocity dispersion
σ
v
=
4.2
−
0.5
+
0.6
km
s
−
1
. We measure the metallicities of 27 member stars of Cen I, and find a mean metallicity Fe/H = −2.57 ± 0.08, and metallicity dispersion
σ
Fe
/
H
=
0.38
−
0.05
+
0.07
. We calculate the systemic proper motion, orbit, and the astrophysical J-factor for each system, the latter of which indicates that Eri IV is a good target for indirect dark matter detection. We also find no strong evidence for tidal stripping of Cen I or Eri IV. Overall, our measurements confirm that Eri IV and Cen I are dark-matter-dominated galaxies with properties largely consistent with other known ultrafaint dwarf galaxies. The low metallicity, right-skewed metallicity distribution, and high J-factor make Eri IV an especially interesting candidate for further follow-up.
•TBT induced caudal fin deformity in killifish embryos.•Susceptibility was the same in PCB-sensitive and PCB-tolerant killifish.•An RXR-ligand recapitulated the TBT-induced caudal fin ...deformity.•Co-treatment with an AHR ligand, PCB126, did not affect the caudal fin deformity.•AHR regulates PPARγ in killifish but PPARγ activity is minimal in embryos.
Tributyltin (TBT) and dioxin-like polychlorinated biphenyls (PCBs) are environmental contaminants that are highly toxic to fish and co-occur in New Bedford Harbor (NBH), an estuarine Superfund site located in Massachusetts, USA. Atlantic killifish (Fundulus heteroclitus) that reside in NBH (and other highly contaminated sites along the east coast of the United States) have developed resistance to activation of the aryl hydrocarbon receptor (AHR) pathway and the toxicity of dioxin-like chemicals, such as 3,3′,4,4′,5-pentachlorobiphenyl, PCB126. In many biological systems, TBT disregulates adipose and bone development via the PPARγ-RXR pathway; AHR activation also disrupts adipose and bone homeostasis, potentially through molecular crosstalk between AHR and PPARγ. However, little is known about how co-exposure and the interaction of these pathways modulate the toxicological effects of these contaminants. Here, we tested the hypotheses that TBT would induce teratogenesis in killifish via activation of PPARγ and that PCB126 co-exposure would suppress PPARγ pathway activation in PCB-sensitive killifish from a reference site (Scorton Creek, SC, PCB-sensitive) but not in PCB-tolerant NBH killifish. Killifish embryos from both populations exposed to TBT (50 and 100 nM) displayed caudal fin deformities. TBT did not change the expression of pparg or its target genes related to adipogenesis (fabp11a and fabp1b) in either population. However, expression of osx/sp7, an osteoblast marker gene, and col2a1b, a chondroblast marker gene, was significantly suppressed by TBT only in SC killifish. An RXR-specific agonist, but not a PPARγ-specific agonist, induced caudal fin deformities like those observed in TBT-treated embryos. PCB126 did not induce caudal fin deformities and did not exacerbate TBT-induced fin deformities. Further, PCB126 increased expression of pparg in SC embryos and not NBH embryos, but did not change the expression of fabp1b. Taken together, these results suggest that in killifish embryos the PPARγ pathway is regulated in part by AHR, but is minimally active at least in this early life stage. In killifish, RXR activation, rather than PPARγ activation, appears to be the mechanism by which TBT induces caudal fin teratogenicity, which is not modulated by AHR responsiveness.
The manufacture and production of industrial chemicals continues to increase, with hundreds of thousands of chemicals and chemical mixtures used worldwide, leading to widespread population exposures ...and resultant health impacts. Low-wealth communities and communities of color often bear disproportionate burdens of exposure and impact; all compounded by regulatory delays to the detriment of public health. Multiple authoritative bodies and scientific consensus groups have called for actions to prevent harmful exposures via improved policy approaches. We worked across multiple disciplines to develop consensus recommendations for health-protective, scientific approaches to reduce harmful chemical exposures, which can be applied to current US policies governing industrial chemicals and environmental pollutants. This consensus identifies five principles and scientific recommendations for improving how agencies like the US Environmental Protection Agency (EPA) approach and conduct hazard and risk assessment and risk management analyses: (1) the financial burden of data generation for any given chemical on (or to be introduced to) the market should be on the chemical producers that benefit from their production and use; (2) lack of data does not equate to lack of hazard, exposure, or risk; (3) populations at greater risk, including those that are more susceptible or more highly exposed, must be better identified and protected to account for their real-world risks; (4) hazard and risk assessments should not assume existence of a "safe" or "no-risk" level of chemical exposure in the diverse general population; and (5) hazard and risk assessments must evaluate and account for financial conflicts of interest in the body of evidence. While many of these recommendations focus specifically on the EPA, they are general principles for environmental health that could be adopted by any agency or entity engaged in exposure, hazard, and risk assessment. We also detail recommendations for four priority areas in companion papers (exposure assessment methods, human variability assessment, methods for quantifying non-cancer health outcomes, and a framework for defining chemical classes). These recommendations constitute key steps for improved evidence-based environmental health decision-making and public health protection.
We present a spectroscopic analysis of Eridanus IV (Eri IV) and Centaurus I (Cen I), two ultra-faint dwarf galaxies of the Milky Way. Using IMACS/Magellan spectroscopy, we identify 28 member stars of ...Eri IV and 34 member stars of Cen I. For Eri IV, we measure a systemic velocity of \(v_{sys} = -31.5^{+1.3}_{-1.2}\:\mathrm{km\:s^{-1}}\) and velocity dispersion \(\sigma_{v}= 6.1^{+1.2}_{-0.9}\:\mathrm{km\:s^{-1}}\). Additionally, we measure the metallicities of 16 member stars of Eri IV. We find a metallicity of \(\mathrm{Fe/H}=-2.87^{+0.08}_{-0.07}\) and resolve a dispersion of \(\sigma_{\mathrm{Fe/H}} = 0.20\pm0.09\). The mean metallicity is marginally lower than all other known ultra-faint dwarf galaxies, making it one of the most metal-poor galaxies discovered thus far. Eri IV also has a somewhat unusual right-skewed metallicity distribution. For Cen I, we find a velocity \(v_{sys} = 44.9\pm0.8\:\mathrm{km\:s^{-1}}\) and velocity dispersion \(\sigma_{v} = 4.2^{+0.6}_{-0.5} \:\mathrm{km\:s^{-1}}\). We measure the metallicities of 27 member stars of Cen I, and find a mean metallicity \(\mathrm{Fe/H} = -2.57\pm0.08\) and metallicity dispersion \(\sigma_{\mathrm{Fe/H}} = 0.38^{+0.07}_{-0.05}\). We calculate the systemic proper motion, orbit, and the astrophysical J-factor for each system, the latter of which indicates that Eri IV is a good target for indirect dark matter detection. We also find no strong evidence for tidal stripping of Cen I or Eri IV. Overall, our measurements confirm that Eri IV and Cen I are dark matter-dominated galaxies with properties largely consistent with other known ultra-faint dwarf galaxies. The low metallicity, right-skewed metallicity distribution, and high J-factor make Eri IV an especially interesting candidate for further followup.
Purpose of Review
Our comparative analysis sought to understand the factors which drive differences in fish consumption advisories across the USA — including exposure scenarios (acute and chronic ...health risk, non-cancer and cancer health endpoints), toxicity values (reference dose, cancer slope factor, acute tolerance level), and meal size and bodyweight assumptions.
Recent Findings
Fish consumption provides essential nutrients but also results in exposure to contaminants such as PCBs and methylmercury. To protect consumers from the risks of fish contaminants, fish consumption advisories are established, most often by state jurisdictions, to estimate the amount of a certain fish species a person could consume throughout their lifetime without harm. However, inconsistencies in advisories across the USA confuse consumers and undermine the public health goals of fish advisory programs. To date, no rigorous comparison of state and national fish consumption advisories has been reported.
Summary
Our work identifies discrepancies in key assumptions used to derive risk-based advisories between US states, reflecting differences in the interpretation of toxicity science. We also address the implications for these differences by reviewing advisories issued by contiguous states bordering two waterbodies: Lake Michigan and the Lower Mississippi River. Our findings highlight the importance of regional collaboration when issuing advisories, so that consumers of self-caught fish are equipped with clear knowledge to make decisions to protect their health.
PDF
