HEALTH CONSULTATION
GROUNDWATER WELLS EAST MOUNT HOUSTON
HOUSTON, HARRIS COUNTY, TEXAS
DISCUSSION
The majority of studies evaluating the health effects of barium are oral exposure studies and include numerous case reports and epidemiologic investigations of humans exposed to barium through accidental or intentional ingestion [1]. Other information on the health effects associated with exposure to barium was obtained from various animal studies involving acute, intermediate, or chronic exposure to barium either by gavage1 or by drinking water.
We were not able to find any studies associating exposure to barium and the development of depression, OCD, or seizures. Both human and animal evidence suggest that the cardiovascular system may be one of the primary targets of barium toxicity. The most commonly observed cardiovascular effects in cases of acute ingestion are hypertension and abnormalities in heart rhythm. One study examining the effect of barium on blood pressure and heart rhythms reported no observable adverse effects in human volunteers drinking the equivalent of 14.7 mg of barium per liter of water per day over a four week period. This concentration of barium is approximately four times higher than the maximum barium concentration measured in Well #1 and approximately eighteen times higher than the maximum concentration of barium in Well #2. Based on available information cardiovascular effects would not be expected; however, no human studies were identified examining longer term exposure to barium compounds [1].
Barium poisoning also has been associated with adverse neurological effects with numbness and tingling around the mouth and neck, occasionally extending to the extremities to be among the first symptoms of barium toxicity. Although the concentrations resulting in these symptoms were not reported in the literature, the symptoms reported were associated with intentional poisonings. Exposures associated with drinking the water from these wells would not be considered intentional poisonings.
Manganese is a naturally occurring substance found in many types of rock and soil. Persons living near a coal or oil-burning factory may be exposed to higher levels of manganese since it is released into air when fossil fuels are burned. Manganese can be found in groundwater as a result of its use in the production of batteries, pesticides, and fertilizers. The average levels of manganese in drinking water have been reported to range from approximately 0.004 mg/L to 0.032 mg/L [2]. The maximum concentration of manganese in water from the residential wells was 1.3 mg/L.
Although the concentration of manganese in the water is greater than the EPA’s secondary drinking water standard for this contaminant (0.05 mg/L), this standard was set for aesthetic reasons and is not health based. Manganese is an essential dietary nutrient; the World Health Organization (WHO) has estimated the average dietary intake of manganese to range from approximately 2 to 8.8 mg/day. The Food and Nutrition Board of the National Research Council has established "estimated safe and adequate daily dietary intake levels" for this nutrient that range from 0 .3 mg per day for infants to 5 mg/day for adults (see Table 3). The WHO had concluded that 8 to 9 mg/day is "perfectly safe" for adults [2]. For most people, food is the primary source of manganese exposure. The Environmental Protection Agency has estimated that the typical human intake of manganese from food is 3.8 mg/day [2].
|
Table 3
Food and Nutrition Board of the National Research
Council’s |
|
| Age Range | Estimated Safe and Adequate Daily Dietary Intake Level |
|
Birth to 6 months |
0.3 to 0.6 mg/day |
| 1 to 3 years | 1.0 to 1.5 mg/day |
| 4 to 6 years | 1.0 to 2.0 mg/day |
| 7 to 10 years | 1.0 to 2.0 mg/day |
| Adolescents > 11 years and Adults | 2.0 to 5.0 mg/day |
Excess exposure to manganese can be harmful to human health. A combination of symptoms resulting in a disease known as manganism has been observed in mining and steel workers after long-term exposure to high levels of manganese dust in the air. These symptoms include weakness, abnormal gait, ataxia2, muscular hypotonicity3, and a fixed facial expression. Manganism occurs when too much manganese adversely affects the brain. Although some of the symptoms of manganism can be treated, the damage that occurs to the brain is permanent [2].
It is not known whether eating or drinking too much manganese can cause manganism. There is one study indicating a statistically significant difference in neurologic test scores between people from one area with high levels of manganese in well water compared with people from another area with low levels of manganese in well water. The concentration of manganese in the water from the high concentration area ranged from 1.8 to 2.3 mg/L; however, because of other limitations this study could not be used to determine a quantitative dose response relationship for the toxicity of manganese in humans [2]. In another report, a group of six Japanese families exposed to manganese in their well water at concentrations of approximately 14 mg/L developed manganism like symptoms [2].
Although no MRLs or RfDs have been established for manganese, ATSDR has used
the upper range of the ESADDI (5 mg/day) to establish an interim guidance value
of 0.07 mg/kg/day [(5 mg/day) /(70 kg)]. Using the maximum reported concentration
of manganese, at this residence an adult would have to drink more than 3 ¾ liters
of water per day before exceeding the interim guidance level. It should be noted
that the interim guidance is based on what is considered to be a safe and adequate
dietary intake and that adverse health effects have not been observed at these
levels.
ATSDR’s CHILD HEALTH INITIATIVE
The TDH has prepared this consult under a Cooperative Agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). TDH has included the following information in accordance with ATSDR’s Child Health Initiative.
ATSDR’s Child Health Initiative recognizes that the unique vulnerabilities of infants and children demand special emphasis in communities faced with contamination of their water, soil, air, or food. Children are at greater risk than adults from certain kinds of exposures to hazardous substances emitted from waste sites and emergency events. They are more likely to be exposed because they play outdoors and they often bring food into contaminated areas. They are shorter than adults, which means they breathe dust, soil, and heavy vapors close to the ground. Children are also smaller, resulting in higher doses of chemical exposure per body weight. The developing body systems of children can sustain permanent damage if toxic exposures occur during critical growth stages. Most importantly, children depend completely on adults for risk identification and management decisions, housing decisions, and access to medical care.
This health consultation evaluated the barium and manganese exposures children would receive through drinking water. These exposures are not expected to result in adverse health effects to children.
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