Natural Background and the Anthropogenic Enrichment of Mercury in the Southern Florida Environment: A Review with a Discussion on Public Health

Mercury (Hg) is a toxic metal that is easily released into the atmosphere as a gas or a particulate. Since Hg has serious health impacts based on human exposure, it is a major concern where it accumulates. Southern Florida is a region of high Hg deposition in the United States. It has entered the southern Florida environment for over 56 MY. For the past 3000 to 8000 years, Hg has accumulated in the Everglades peatlands, where approximately 42.3 metric tons of Hg was deposited. The pre-industrial source of mercury that was deposited into the Everglades was from the atmosphere, consisting of combined Saharan dust and marine evasion. Drainage and the development of the Everglades for agriculture, and other mixed land uses have caused a 65.7% reduction in the quantity of peat, therefore releasing approximately 28 metric tons of Hg into the southern Florida environment over a period of approximately 133 years. Both natural and man-made fires have facilitated the Hg release. The current range in mercury release into the southern Florida environment lies between 994.9 and 1249 kg/yr. The largest source of Hg currently entering the Florida environment is from combined atmospheric sources, including Saharan dust, aerosols, sea spray, and ocean flux/evasion at 257.1-514.2 kg/yr. The remobilization of Hg from the Everglades peatlands and fires is approximately 215 kg/yr. Other large contributors include waste to energy incinerators (204.1 kg/yr), medical waste and crematory incinerators (159.7+ kg/yr), and cement plant stack discharge (150.6 kg/yr). Minor emissions include fuel emissions from motorized vehicles, gas emissions from landfills, asphalt plants, and possible others. No data are available on controlled fires in the Everglades in sugar farming, which is lumped with the overall peatland loss of Hg to the environment. Hg has impacted wildlife in southern Florida with recorded excess concentrations in fish, birds, and apex predators. This bioaccumulation of Hg in animals led to the adoption of regulations (total maximum loads) to reduce the impacts on wildlife and warnings were given to consumers to avoid the consumption of fish that are considered to be contaminated. The deposition of atmospheric Hg in southern Florida has not been studied sufficiently to ascertain where it has had the greatest impacts. Hg has been found to accumulate on willow tree leaves in a natural environment in one recent study. No significant studies of the potential impacts on human health have been conducted in southern Florida, which should be started based on the high rates of Hg fallout in rainfall and known recycling for organic sediments containing high concentrations of Hg.

Natural Radiation in the Rocks, Soils, and Groundwater of Southern Florida with a Discussion on Potential Health Impacts

Southern Florida is underlain by rocks and sediments that naturally contain radioactive isotopes. The primary origin of the radioactive isotopes is Miocene-aged phosphate deposits that can be enriched in uranium-238 and its daughter isotopes. Nodular phosphate containing radionuclides from the Miocene has been reworked into younger formations and is ubiquitous in southern Florida. When the nodular phosphate is exposed to groundwater with geochemical conditions favorable for its dissolution, uranium, radium, and radon may be released into the groundwater system. Uranium concentrations have been measured above the 30 µg/L drinking water standard at only one location in Lee County. Radium226/228 exceedances of the drinking water standard have been documented in numerous wells in Sarasota County. Indoor radon activities have exceeded the 4 piC/L guideline in five southern Florida counties. The exceedance of radioactivity standards in drinking water does not occur in municipal drinking water supplies, but rather only in some domestic self-supply wells. Health risks for exposure to radiation from domestic self-supply wells could be mitigated by testing of well water and, if necessary, switching to the use of a different aquifer or treatment process. While the risk of exposure to radon in indoor air in southern Florida is generally low, some areas are enriched in soil radon that migrates into structures, which could be addressed by improved ventilation.

Predictors of Endophthalmitis after Intravitreal Injection: A Multivariable Analysis Based on Injection Protocol and Povidone Iodine Strength

PURPOSE

To determine the incidence of endophthalmitis after anti-vascular endothelial growth factor (VEGF) therapy at our institution and to identify potential risk factors for endophthalmitis occurring after injection.

DESIGN

Retrospective, single-center cohort study.

PARTICIPANTS

All patients who received an intravitreal injection of an anti-VEGF medication between January 1, 2014, and March 31, 2017.

METHODS

Current Procedural Terminology and International Classification of Diseases billing codes were used to identify instances of anti-VEGF administration and cases of endophthalmitis. Medical records and injection technique were reviewed carefully in each case. Multivariable logistic regression analysis was performed in a stepwise fashion to determine independent predictors of endophthalmitis based on injection protocol.

MAIN OUTCOME MEASURES

Incidence of endophthalmitis after injection and odds of endophthalmitis by injection technique with 95% confidence intervals (CIs).

RESULTS

A total of 154 198 anti-VEGF injections were performed during the period of interest, resulting in 58 cases of endophthalmitis (0.038% [1:2659]). After adjustment for confounders, both 2% lidocaine jelly (odds ratio [OR], 11.28; 95% CI, 3.39-37.46; P < 0.001) and 0.5% Tetravisc (Ocusoft, Richmond, TX; OR, 3.95; 95% CI, 1.15-13.50; P = 0.03) use were independent risk factors for endophthalmitis after injection. Lid speculum use, povidone iodine strength (5% vs. 10%), injection location (superior or inferior), conjunctival displacement, use of provider gloves, use of a strict no-talking policy, use of subconjunctival lidocaine, and topical antibiotic use were not statistically significant predictors of endophthalmitis after injection. There was no difference in endophthalmitis rate among the anti-VEGF agents (bevacizumab, ranibizumab 0.3 mg, ranibizumab 0.5 mg, and aflibercept).

CONCLUSIONS

The incidence of endophthalmitis after anti-VEGF injections is low. Use of lidocaine jelly or Tetravisc may increase the risk of endophthalmitis after injection.

High-resolution maps of regional ventilation utilizing inhaled fluorescent microspheres

The regional deposition of an inhaled aerosol of 1.0-micron diameter fluorescent microspheres (FMS) was used to produce high-resolution maps of regional ventilation. Five anesthetized, prone, mechanically ventilated pigs received two 10-min inhalations of pairs of different FMS labels, accompanied by intravenous injection of 15.0-micron radioactive microspheres. The lungs were air dried and cut into 1.9-cm3 pieces, with notation of the spatial coordinates for each piece. After measurement of radioactive energy peaks, the tissue samples were soaked in 2-ethoxyethyl acetate, and fluorescent emission peaks were recorded for the wavelengths specific to each fluorescence label. The correlation of fluorescence activity between simultaneously administered inhaled FMS ranged from 0.98 to 0.99. The mean coefficient of variation for ventilation for all 10 trials (47.9 +/- 8.1%) was similar to that for perfusion (46.2 +/- 6.3%). No physiologically significant gravitational gradient of ventilation or perfusion was present in the prone animals. The strongest predictor of the magnitude of regional ventilation among all animals was regional perfusion (r = 0.77 +/- 0.13).

Biological availability of lead in a paint aerosol. 1. Physical and chemical characterization of a lead paint aerosol

This study was conducted to determine the physical and chemical characteristics of an aerosol of lead-based paint, generated in an industrial spray operation, that might influence the biological availability of lead present in inhaled aerosols. Paint aerosols were collected, and mass-size distribution was determined using a portable cascade impactor under actual occupational conditions. Approx. 2% of the particulate mass collected was in the respirable range (less than 10 micron mean aerodynamic diameter), although the maximum airborne concentration of lead was found to be 2-3 mg/m3. The lead concentration in a dried aerosol was very resistant to chemical digestion. Analysis by X-ray diffraction, atomic absorption spectroscopy and inductively coupled plasma emission spectroscopy showed approx. 11% lead by dry weight, although the wet weight concentration of lead reported by the manufacturer was 12.8%.

The chemical neutralization of inhaled sulfuric acid aerosol

We hypothesize that gaseous ammonia (NH3) released into respiratory airways can neutralize inhaled acidic particles and alter or mitigate their toxicity. To test this hypothesis, we have examined the relationship between respiratory NH3 and the chemical neutralization of inhaled sulfuric acid (H2SO4) aerosol in the surgically isolated upper airways of anesthetized dogs. With air entering via the mouth, the NH3 concentration measured at the larynx, ranged between 30 and 225 parts per billion (ppb). The extent of neutralization at this point ranged from 8%-70% (n = 16) for the 0.5-micrometer particles and 7%-22% (n = 16) for the 1.0-micrometer particles. With air entering via the nose, the laryngeal NH3 concentrations ranged between 50 and 220 ppb. Neutralization values were between 15%-65% (n = 8) for 0.5-micrometer particles, and between 16%-18% (n = 3) for 1.0-micrometers particles. For both routes of entry, the extent of neutralization was correlated with the laryngeal NH3 concentration. We conclude that the chemistry of acidic particles is significantly altered by respiratory NH3 during inhalation. The extent of neutralization is related to both the NH3 concentration in the airway and the size of the particle entering the airway. The extent of neutralization per ppb of laryngeal NH3 is related to the route of entry, being greater for the mouth than the nose.

Relationships of temperature and sodium chloride concentration to the survival of Vibrio parahaemolyticus in broth and fish homogenate

The interaction of temperature and NaCl concentration in affecting the survival of three strains of Vibrio parahaemolyticus was studied in Trypticase soy broth and fish homogenate. Cells of V. parahaemolyticus suspended in Trypticase soy broth without NaCl were quite unstable and readily killed. The presence of NaCl appeared to be protective to the cells at 48 +/- 1 C, with the optimal concentration strain-dependent for the 3 to 12% range tested. Temperatures of 5 +/- 1, -5 +/- 1, and -18 +/- 1 C reduced the number of viable organisms per milliliter regardless of the NaCl concentration. In the presence of NaCl, viable cells, in numbers ranging up to 580 per ml, were still detected at the end of 30 days of storage. Similar results were obtained for cells suspended in fish homogenate, except that fish homogenate itself was protective as compared with Trypticase soy broth. This protection was significantly lower than that provided by NaCl in any amount tested.