The tropical storm Harvey began in the Gulf of Mexico on Aug. 17, growing into a Category 4 hurricane by Aug. 25 as it hit Texas, with 130 mph winds, heavy rains, and a massive storm which slowed down to about 40 mph by Aug 27. However, Houston along with the southeastern Texas had already been inundated with a year’s-worth of rain in less than a week. Two flood-control reservoirs were broken increasing water levels throughout the Houston area by August 29 (2).
Houston area had the largest rainwater ever noted in the continental United States from a single storm (51.88 inches) (3). As of October 14, at least 75 fatalities were confirmed in Houston-area and most of them were from drowning; 36 in Harric County, 6 in Galveston, 4 in Montgomery and 3 in Fort Bend (5). An estimated damage of $198 billion to residential and commercial structures and contents and public infrastructure occurred due to Hurricane Harvey (6).
Because Houston has some 2 dozen Superfund sites, floodwater contamination with toxic chemicals was of major concern in Houston. Additionally the abundance of private water wells made the situation worrisome (7).
As of October 6 according to the EPA, 2,238 drinking water systems were affected out of which 2,014 systems were fully operational, 77 had boil-water notices, and 19 were shut down in the state. The TCEQ contacted 1,219 wastewater treatment plants in the 58 counties within the Governor’s Disaster Declaration and 31 of those were inoperable in the affected counties. TCEQ confirmed that only 15 dams suffered some damage out of 340 dams in the impacted areas that they had contacted. No reports of downstream damage or loss of life was reported (8).
The flood water was also found to have E. coli and coliform bacteria in concentrations so high that there were risks of contracting flesh-eating disease from the water (12).
Current situation in Houston
As the temporary armored cap on the San Jacinto waste pits located along the banks of the San Jacinto River (SJRWP) east of Houston, Texas, USA was broken during Harvey it leaked (1) and subsequent testing revealed by the EPA revealed 70,000 ng/kg of dioxin near the pit while the recommendation for cleanup is above 30 ng/kg (2). The cap has been initially designed to last for up to 100 years but it has suffered damages and leakages in the past requiring extensive repairs at least six times in recent years (3).
What is dioxin?
The World Health Organization (WHO) defines “dioxins and dioxin-like substances as a polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) often having similar toxicity profiles and common mechanisms of action”. They are produced as by-products of industrial processes like the manufacture of chlorophenols and phenoxy herbicides, chlorine bleaching of paper pulp and smelting. They can also be generated by natural events, such as volcanic eruptions and forest fires”. Around 419 types of dioxin-related compunds have been identified and 30 of them have substantial toxicity with 2,3,7,8- tetrachlorodibenzo para dioxin (TCDD) being the most toxic of all (4). PCDD and PCDF congeners are class 1 human carcinogens since they have been shown to be associated with severe developmental and hormonal defects as well as immune suppression in animal models at low concentrations (5).
In human body, dioxins have a half-life of 7 to 11 years because of their chemical stability and affinity for fats (4). The half-life of TCDD has been estimated to be 9-15 years on surface soil, and 25-100 years in sub-surface soil (6). They can be transported to long distances and can move easily from land to air and water (6), persist in the environment, and undergo bioaccumulation in the food chain up to levels that can be harmful to human and ecological health (4,6). They bind to soils and sediments very strongly because of their low vapor pressure, low water solubility, and strong ability to adhere to particulates (6). Though major exposure route is diet small exposures occur through other routes including absorption through skin from contact with water (6) .
Chloracne, patchy darkening of the skin, and altered liver function are the most common side effects of short-term exposure to high concentrations of dioxins. Longer-term exposure can be highly toxic leading to cancer, immune system damages, developmental and reproductive problems and interference with hormones (4). Especially fetuses, infants, and children are the most vulnerable population to dioxin exposure because of their rapid growth and development (6)
EPA has worked with industries to reduce the production and exposure to dioxins (7) and hence dioxin concentrations in the US have been decreasing over the past 3 decades but because of the long half-life (6) current exposure is from the dioxins that were produced in the past (7).
The San Jacinto River Waste Pits (SJRWP) has three pits, located on the west bank of the San Jacinto River near the Interstate -10 (I 10) bridge. The site was filled with paper mill waste high in polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in the 1960s and 1970s (8).
The eastern pits are partially submerged in river water and often gets completely inundated during high flows or tide events. Additionally, the pit area has subsided along with the surrounding land (9).
The site was listed as a National Priorities List of hazardous waste sites in 2008 and since then EPA started overseeing it. Champion Paper was the primary source of the waste relese at the site which is now bought by the International Paper. EPA assigned McGinnis Industrial Maintenance Corporation (a subsidiary of Waste Management) and International Paper, as the potentially responsible parties (PRPs) for the site clearance and management. Following EPA’s direction, a temporary armored cap was installed on the pits north of I-10 by the PRPs in July 2011 (10).
However, the EPA realized that the cap plan was an unreliable long-term solution and called for waste removal, soil excavation, and other remediation efforts, at the cost of $96.9 million, in 2016 which was to be paid by the PRPs. (9)DR1 .
Exposure and health risks associated with dioxin at the SJRWP
Though comprehensive studies on dioxins at sites surrounding the superfund site is outdated, data from a multilayer dioxin monitoring study showed the presence of dioxins in surrounding areas connected to the SJR including the immediate area around the Superfund site itself situated under the 1–10 overpass. Sediment sampling from 2002 to 2011 from 47 different location as shown in the (fig 1) across 11 key bodies of water connected to the San Jacinto River (SJR) showed up to 17 toxic PCDD/PCDF congeners. The PCDDF/ PCDF congeners found at the highest concentrations also included 2,3,7,8 TCDD, the most toxic form of dioxins summarized below in fig 4 (11).
Map of the San Jacinto River and Houston Ship Channel collection region from 2002 to 2011. The region highlighted in red denotes the borders of the SuperfundDR2 site. Sampling stations across the SJR discussed in this review are color coded to 11 different areas as follows: Bear Lake—pink; Superfund—aqua; Lost Lake—blue; Buffalo Bayou—yellow; Burnet Bay—light pink; Scott Bay—green; Tabbs Bay—light blue; San Jacinto Bay—red; Black Duck Bay—dark blue, Mouth of SJR—purple, Galveston Bay—orange
Fig. 4 Average TEQ for subdivided regions of the San Jacinto River system and Houston Ship Channel
In general, PCDD/PCDF TEQ seemed to decrease I concentration l based on the data available before 2011 except for the Buffalo Bayou and the Upper San Jacinto Bay (11). However data to predict the effectiveness of the armored cap in containing the dioxins at the SJRWP since 2011 after its installation are lacking (11).
Health concerns in the Eastern Harris County
A report from the Texas Department of State Health Services in 2015 following data analysis for an 18-year period spanning from 1995 to 2012 showed significantly high rate of brain, cervical, kidney, and rare retinoblastoma cancer were seen in Eastern Harris County especially in the three census tracts 2525, 2529, and 2533 bordering the SJR waste pits to the west, north/northeast, and east/southeast (Fig. 5). According to the report, “tract 2525 to the west, in which Buffalo Bayou acts as a natural border, was noted for elevated rates of cervical cancer were noted in tracts 2525, abnormally high rates of cervical and kidney cancer in addition to rare retinoblastoma cancer were observed in children in tract 2529 to the north, and high cases for brain cancer were observed in tract 2533 to the east/southeast had. Number of cervical cancer in adults was more than double the expected number with a total of 21 confirmed cases across both 2525 and 2529 census tracts. Brain cancer was also double the expected number in 2533 with a total 10 adult cases, kidney cancer was present at 1.5 times the expected value with 33 cases in 2529, and retinoblastoma cancer was over 16 times the expected value with 5 known cases in tract 2529” (12).
Map of three census tracts identified as cancer clusters in relation to the waste pits and two representative sampling stations (11)
However Texas Department of State Health Services (DSHS) and Agency for Toxic Substances and Disease Registry (ATSDR) had concluded in 2013 that brain, kidney, cervical, and retinoblastoma cancer cannot be a typical carcinogenic endpoints for acute TCDD exposure with regards to the exposure around the SJR (8).
They also believed that the groundwater and surface water near the SJRWP site do not present as hazard to public health since the groundwater and surface water near the site are brackish and not used for drinking purposes, and the nearest residence being nearly ½ mile from the site, shallow groundwater contamination is less likely to be a health hazard in case contamination has occurred. Furthermore, they also claimed that dioxins being poorly soluble in water and tightly bound to sediments, surface water contamination is less likely to pose a significant health hazard (8).
An addendum to the previous report by DSHS concluded that though “the two cancers of concern, childhood retinoblastoma and glioma, appear at many times the expected rate in a few census tracts. However, there are a very small number of observed cases (five or fewer)” which makes epidemiological s environmental exposures study difficult, and there has been no scientific literatures to show association between childhood cancers and environmental exposures, and that the experts consulted didn’t see “any trends emerge in the data in terms of location, distribution, or frequency of cases that would indicate the need for additional studies to attempt to identify specific environmental causes”, concluded that would continue to count and monitor cancer statistics for Harris County in the future but would not pursue additional epidemiological study realte dto the cancer occurrence (12).
Since, there are evidences that the groundwater around the Superfund site might not be as safe as it had been previously regarded. Private wells near the Superfund have been to have low levels of PCDD/PCDF congeners in the well water (13) and it has been said that as high as 28 wells out of 100 ground water sites tested were found to be contaminated with dioxins (14).
It’s difficult to estimate the level of dioxin that might have escaped into the river and surrounding areas. The river and downstream water bodies which are not restricted for fishing or recreational activities might be a health hazard n case the dioxin has been released during the Harvey.
What is being done?
A temporary installation of the armored cap to contain the leakage was the first response which was finished in 2011 (15). Complete removal of the waste from the Superfund site has been a controversial issue. The high cost associated with the excavation and transportation and the assumption that doing so would increase the risk of sediments being disturbed by storms or floods. Advocates of the armored cap believe that strengthening the existing cap could be the better option to contain the contaminants (15).
However, it is clear that the EPA has announced the cap idea as an unreliable long-term solution and called for waste removal, soil excavation, and other remediation efforts, at the cost of $96.9 million, in 2016 which was to be paid by the PRPs. (9)DR3 .
On Oct 11, 2017, the approved cleanup plan to address the dioxin contamination at the SJWRP was shared by the EPA (16). The EPA’s final action for the San Jacinto River Waste Pits Site includes “excavation and off-site disposal of source materials and contaminated soils from the pits in and adjacent to the San Jacinto River” which will cost $97 million. It says that Institutional Controls (ICs) will be employed so as not to disturb the sediments while it will use Monitored natural recovery (MNR) for sediment in the neighbouring sand separation area to protect the aquatic environment. The plan includes the following major actions;
i. “Removal of a portion of the existing temporary armored cap installed under the time critical removal action (TCRA)”.
ii. “Removal of approximately 162,000 cubic yards (cy) of waste material exceeding the
paper mill waste material cleanup goal of 30 nanograms per kilogram (ng/kg) 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) toxicity equivalent (TEQ) that is located
beneath the armored cap in the northern impoundment. The waste material will be
stabilized as necessary to meet the appropriate requirements at a permitted disposal
iii. Excavation of approximately 50,000 cy of waste material exceeding the paper mill waste
material and soil cleanup goal for the Southern Impoundment of 240 ng/kg TEQ to a depth of 10 feet below grade in the peninsula south of I-10.
This remedy is believed to result in the residual contaminants at the site above levels which will allow for unlimited use and unrestricted exposure. This will be followed by statutory reviews at least once every five years to ensure protection of human health and environment. Depending on the review, further corrective programs may be added to remove, treat, or contain the contaminants (10).
DR1Need to find if it was approved
DR2Discuss the legends with Elise-not sure
DR3Need to find if it was approved