PUBLIC HEALTH ASSESSMENT
VASQUEZ BOULEVARD AND I-70
DENVER, DENVER COUNTY, COLORADO
DISCUSSION OF THE PUBLIC HEALTH SIGNIFICANCE OF CONTAMINANTS
Possible Health Effects from Exposures to Arsenic
Background: Human studies about the health effects of arsenic
ATSDR reviewed the findings from numerous studies that have documented the effects of arsenic on humans. Most of these studies examined what happens to people who drink water contaminated with arsenic. Though drinking contaminated water does not appear to be an important exposure pathway at VBI70, the results of these studies are relevant for evaluating effects of accidentally or purposely ingesting soils contaminated with arsenic. Findings from three of the studies on arsenic toxicity are presented here:
The most common outward effects of arsenic exposure are hyperpigmentation and keratosis. Appendix G contains photographs of hyperpigmentation on someone's arm and keratosis on someone's hands and heals. The keratosis in Appendix G is a severe case of keratosis. The youngest person to experience increased skin pigmentation in the Taiwan study was 3 years old; the youngest person to experience keratosis was 4 years old; and the youngest person to experience skin cancer was 24 years old. Appendix G also has a photograph of arsenical-induced skin cancer. The number of people who experienced health effects increased with each decade of exposure to arsenic in drinking water with the highest number of cases occurring when people were 60 to 70 years old. This study showed that while young children can experience harmful effects from arsenic, generally long-term exposure for many decades are required before many cases will appear in a community (ATSDR 2000.)
Many studies exist for arsenic exposure in India and Bangladesh and so a wide range of arsenic levels in water have been found. In one such study, arsenic levels ranged from less than 50 ppb to over 800 ppb with the highest level detected being 3,400 ppb. Over 80% of the population, however, used drinking water with arsenic levels below 500 ppb. In this study of 7,683 people, the authors found 12 cases of keratosis and 27 cases of hyperpigmentation in people drinking water containing between 50 and 100 ppb arsenic. Using an average of 75 ppb and a range of water intakes (2 liters per day to 4 liters per day), the estimated daily intake of arsenic for this group ranges from 150 to 300 micrograms arsenic per day (Mazumder 1998). The authors, however, stress that some uncertainty exists in classifying people as to their arsenic intake.
Arsenic levels in drinking water for this population ranged from 600 to 800 ppb and people were exposed for a maximum of 12 years. Estimated daily arsenic intake for these children is probably around 600 to 1,600 micrograms per day depending on how much water they drank. After 4 years of exposure, children were found with a variety of health effects.
Arsenic is known to cause skin irritation in the workplace causing redness and swelling after contact with arsenic dust (ATSDR 2000). One question that arises for the smelter episode is whether or not arsenic exposure alone was responsible for causing skin irritation in children or whether sulfur dioxide is needed. This prompted the authors to apply arsenic trioxide to the skin of rabbits. Skin irritation in rabbits occurred only when the authors applied arsenic trioxide between the skin folds of rabbits. Apparently, the arsenic trioxide does not cause open sores from direct skin contact but rather from the combination of moisture, arsenic trioxide, and the rubbing action that occurs in the folds of skin. It may also be the case that sulfur dioxide in the smelter episode increased the potential of arsenic trioxide to cause skin irritation.
Unfortunately, the authors did not test extensively the environment that the children played in, although grass was found to contain 925 ppm arsenic. Therefore, it is not possible to know exactly how much arsenic was in the children's play area that resulted in skin effects (Birmingham et al. 1965).
Overall, the studies have one important finding in common: high exposure to arsenic for many years has the potential to cause harmful health effects in both children and adults. ATSDR's evaluation of the VBI70 site considers the findings of the previous studies and many other studies showing the effects of arsenic on humans. ATSDR compares site-specific estimates of exposure to arsenic in VBI70 residents to exposure levels presented in the previously mentioned studies.
Uncertainty issues in deciding possible adverse health effects
Uncertainty based on estimated exposure
Much of the uncertainty involved in deciding whether or not adverse health effects might occur comes from estimating how much arsenic people are exposed to from living in properties with arsenic-contaminated soil. As mentioned previously, some children and adults are exposed to arsenic in soil from hand-to-mouth activity. This activity results in varying amounts of ingested soil each day. For children, studies lasting a couple of weeks have shown that most children ingest between 10 and 50 milligrams (mg) a day while a smaller group of children ingest up to 200 mg a day. A recent study of 64 preschool children who live in Anaconda, Montana, showed an average soil intake of 30 mg a day and a maximum soil intake of about 200 mg a day (Stanek and Calabrese 2000). Uncertainty arises in using these average and near maximum values for the following reasons:
Most public health agencies in the United States use 200 mg soil a day to estimate exposure in preschool children with high soil intake. In this evaluation, ATSDR will use this value as well as 30 mg soil a day to estimate exposure for preschool children with typical soil intake. When estimating exposure in other age groups, ATSDR will use 30 and 100 mg soil a day for elementary school children, teenagers, and adults.
At the VBI70 site, children with soil-pica behavior are a special concern to the agency because ingesting high amounts of soil could lead to significant arsenic exposure. The information that is available is reported in Discussion of Exposure Pathways Section in the subsection about soil-pica. The uncertainty that exists when evaluating soil-pica follows:
No studies have been conducted specifically in the VBI70 study area to gather information about the different points raised in the previous bullets. Therefore, ATSDR has to rely on the limited information from other studies about soil-pica. As previously mentioned, soil-pica children may eat as much as 5,000 milligrams (or about 1 teaspoon) of soil at a time, and that soil-pica children can eat soil one time, or three or four times during a week for several weeks.
Uncertainty based on arsenic toxicity
Uncertainty when deciding about possible adverse effects also exists because of how arsenic interacts with the human body. Not all the arsenic that is eaten actually gets into the body since some arsenic will pass through someone's system. For example, some arsenic is bound so tightly to soil particles that it is less likely to be absorbed by the lining of the intestinal tract (the gut) than arsenic bound loosely to soil particles. This phenomenon of how much arsenic actually crosses the gut and gets into the body is called bioavailability. For instance, if only half of the arsenic in soil is capable of getting into someone's body, the soil arsenic is referred to as being 50 percent bioavailable. The uncertainty at the VBI70 site is what percentage of arsenic in soil is bioavailable to humans when they ingest it. For the VBI70 site, ATSDR assumed an upper range of bioavailability to be between 40 and 60 percent.
In addition, if someone has eaten recently, the time it takes for arsenic to be absorbed through the gut might increase and this might change the degree to which arsenic will cause harmful effects. Additional uncertainty comes from the studies where arsenic is usually dissolved in water or some other fluid. In such cases, chemicals dissolved in water tend to mix more readily in the contents of the intestinal tract that are near the absorption sites (Gilman et al. 1993). Since the arsenic is already dissolved in water and in close contact with the intestinal tract, it is likely to be more quickly absorbed by people compared to arsenic bound to soil. Therefore, the health effects that are reported from drinking water studies may or may not reflect the possibility of health effects in people who ingest soil containing arsenic.
Possible skin irritations
At the VBI70 site, children who play in arsenic-contaminated soil and adults who garden in arsenic-contaminated soil could easily get arsenic-bound soil on their skin, particularly in the folds of the skin around their knees and elbows. What is uncertain at this point is whether or not arsenic levels at the more highly contaminated properties (for instance, arsenic levels above 1,000 ppm) could cause the same skin effects as found in children who lived near the previously described Utah smelter and who were similarly exposed to arsenic in soil and dust. Although it is uncertain at this time because of limited scientific data, a concern exists that arsenic at the most highly contaminated properties might cause skin irritation. If skin irritation occurs from contact with arsenic in soil, possible symptoms include:
In addition to these skin effects, direct contact with arsenic-contaminated soil might also cause irritation of the eyes and nasal passages. Such harmful effects have been seen in occupational exposures and in one community where residents were exposed to arsenic in the environment. It seems unlikely that low levels of arsenic in soil could cause these harmful effects.
Background information on evaluating soil ingestion
As previously mentioned, children have a range of soil intakes with a daily average soil intake somewhere around 30 to 60 milligrams (mg) (about 1/16 teaspoon). For instance, a child might have a daily soil intake for a week that looks like this: 10 mg, 40 mg, 30 mg, 5 mg, 90 mg, 50 mg, and 20 mg, which averages out to be 35 mg a day. This intake probably results from daily hand-to-mouth activity. Some children have a higher daily average and studies have shown that average daily soil intake for these children is somewhere between 100 and 200 mg. For these children with typical soil intakes, some will practice soil-pica behavior. Studies have shown that the amount of soil ingested during a soil-pica episode varies and ranges from levels above 200 mg to 5,000 mg or more. For instance, a study of children living near a smelter site in Montana found one child with a soil-pica intake of 600 mg. Typical soil-pica intakes are probably around 5,000 mg (Stanek and Calabrese 2000, Calabrese and Stanek 1993, Calabrese et al. 1989, Wong 1988). To estimate exposure from soil intake, ATSDR used a range of soil ingestion rates. The range includes the following amounts of soil: 30 mg, 60 mg, 200 mg, 600, 1,000 mg, 3,000 mg, and 5,000 mg of soil.
Another factor to consider for soil-pica children is the frequency of soil-pica episodes. To incorporate frequency, ATSDR assumed a one-time soil-pica episode and a 3-day soil-pica episode over a week or for several weeks. Since it is reasonable to assume that a preschool child might play in the most contaminated part of a yard, ATSDR used the estimated maximum arsenic level in the property based on Phase III data. To estimate the maximum arsenic level, ATSDR used the average arsenic level in the yard and the regression formula described previously.
To determine if harmful effects might be possible ATSDR first compared the estimated amount of arsenic exposure (or dose) to the Agency's "health guideline" dose for acute exposures to arsenic. The health guideline dose or Minimal Risk Level is an exposure level below which you would not expect to find harmful health effects.(20) In the case of arsenic, ATSDR has developed a provisional acute oral Minimal Risk Level (MRL) for arsenic of 0.005 mg/kg/day.(21) The MRL was is based on several transient (i.e., temporary) effects and include nausea, vomiting, and diarrhea. The dose of 0.005 mg/kg/day means 0.005 milligrams of arsenic per kilogram body weight per day. When an estimated acute dose of arsenic is below 0.005 mg/kg/day, then non-cancerous harmful effects are unlikely. It is important to note several things about the MRL:
Possible non-cancerous health effects in children with typical soil intake
Teenagers, elementary-school children, and most preschool children are not at risk of harmful effects from arsenic in soil, even at the more highly contaminated properties. (Note that the risk of cancer is discussed separately in a following subsection.) There are several reasons for this conclusion:
Table 5 shows the estimated dose for children in different age groups with different soil intakes at the property with the highest arsenic contamination based on Phase III data. Appendix H describes how ATSDR estimated these doses.
Table 5. Estimated dose for children in different age groups with different soil intakes at the property with the highest arsenic contamination based on Phase III data
| Age Group | Soil Intake mg |
Estimated Arsenic Dose mg/kg/day |
Provisional Acute MRL mg/kg/day |
Above or Below |
| Preschool Children 1-year-old |
30 | 0.008 | 0.005 | Above |
| Preschool Children 1-year-old |
60 | 0.02 | 0.005 | Above |
| Preschool Children 1-year-old |
200 | 0.05 | 0.005 | Above |
| Elementary-Age Children | 30 | 0.002 | 0.005 | Below |
| Elementary-Age Children | 60 | 0.004 | 0.005 | Below |
| Teenagers | 30 | 0.002 | 0.005 | Below |
| Teenagers | 60 | 0.003 | 0.005 | Below |
| Adults | 60 | 0.003 | 0.005 | Below |
Under certain situations the estimated amount of arsenic exposure in some preschool children might exceed ATSDR's provisional acute MRL for arsenic. Using the estimated maximum arsenic level from the property in Phase III with the highest arsenic contamination, the estimated amount of arsenic exposure for 1-year-old preschool children who ingest 30, 60, or 200 mg soil exceeds ATSDR's provisional acute MRL at some properties. Exceeding an MRL does not automatically mean that harmful effects are possible because a safety factor is incorporated into developing the MRL. In other words, the actual dose that causes harmful effects is much higher than the MRL. In this case, the estimated dose at 30 and 60 mg soil still is sufficiently below the dose that causes harmful effects. Therefore, harmful effects are unlikely. For 1-year-old preschool children who ingest 200 mg soil and who live at the most contaminated property, their estimated dose of 0.05 mg/kg/day is the same as the dose in a human study that caused temporary harmful effects.
Possible health effects that might occur include:
It should be noted that several conditions need to exist for these temporary harmful effects to occur. The conditions include:
In reviewing Phase III data, only one property, which has an average arsenic level of 759 ppm, has estimated exposure doses in preschool children who ingest 200 mg soil that are at levels that might cause harmful effects. As part of their cleanup efforts, EPA has cleaned up this property.
Appendix H describes the quantitative methods ATSDR used to estimate arsenic doses in children with typical soil intake.
Possible non-cancerous health effects in soil-pica children
One-time exposure
As mentioned previously, soil-pica children have varying amounts of soil intake ranging up to 5,000 mg or more. Table 6 shows the estimated doses in soil-pica children with varying amounts of soil intake for the property with the highest arsenic contamination in Phase III sampling data. The average arsenic level at this property is 759 ppm with an estimated maximum arsenic level of 4,856 ppm. Appendix H shows how ATSDR estimated doses to soil-pica children.
For this property, the estimated doses should a soil-pica episode occur at the most contaminated part of yard significantly exceeds ATSDR's provisional acute MRL for arsenic and is well above the level of 0.05 mg/kg/day that is known to cause temporary effects in humans.
If soil-pica children ingest large amounts of soil from the most contaminated part of a yard, about 650 of the 2,986 properties sampled so far in the VBI70 study area could be a concern for soil-pica children. Based on EPA's baseline risk assessment, EPA has identified properties as a concern for children with soil-pica behavior if the property has an average arsenic level in soil of 47 ppm or greater. Based on demographic information, about 300 preschool children live in these 650 households and somewhere between 12 to 60 of these children might have soil-pica behavior some time during their preschool years.
The health effects that might occur in some soil-pica children at these properties depend upon where in the yard children eat soil and how much soil children eat. It also depends on how quickly and how much arsenic is released from the soil particles and is absorbed through the gut. In this case, ATSDR used a range of 40 to 60 percent to estimate the bioavailability of arsenic. In addition, ATSDR's description of the possible health effects assumes that the harmful effects that might occur from arsenic in soil is similar to the harmful effects that might occur from arsenic in liquids (for instance, drinking water). As mentioned previously, these factors add some uncertainty and variation in estimating the dose and deciding which health effects might occur.
Table 6. Estimated doses for 1-year-old soil-pica children in comparison to ATSDR's provisional acute MRL
| Soil Intake mg |
Estimated Arsenic Dose mg/kg/day |
Provisional Acute MRL mg/kg/day |
Above or Below |
| 600 | 0.2 | 0.005 | Above |
| 1000 | 0.3 | 0.005 | Above |
| 3000 | 0.8 | 0.005 | Above |
| 5000 | 1.3 | 0.005 | Above |
For properties where at least one of the composite samples exceeds 47 ppm, the most likely symptoms that soil-pica children might experience from a one-time soil-pica episode include:
If these health effects occur, they will likely disappear within a few days provided that soil-pica behavior in contaminated parts of the yard stops.
It is important to note that about one thousand residential properties have not been sampled in the VBI70 study area and that some of these properties will have dangerous levels of arsenic in soil. About 200 of these one thousand properties might have arsenic levels that are a concern for soil-pica children.
To evaluate arsenic exposure that occurs more than one time, it is necessary to average the arsenic dose over the period of exposure. Instead of using the previously described dose of 0.05 mg/kg/day as an indicator of possible health effects, other studies sometimes become more important in deciding the possibility of harmful effects. This situation exists for arsenic when exposures occur for a week. In this case, a study reported by Armstrong et al. showed that people exposed to arsenic for a week at 2 mg/kg/day resulted in very serious health effects. Since soil-pica behavior can be habitual and occur several times in a week, ATSDR estimated arsenic doses to habitual soil-pica children.
The dose to a soil-pica child for a weekly exposure is likely to be lower than the daily dose. The reason for this is that soil-pica behavior is less likely to occur every day throughout the week. It is more reasonable to assume that some children could exhibit soil-pica behavior three or four times a week. Since soil-pica behavior is likely to be less frequent when looking at a week of exposure, the dose should be averaged over the week. For those children who live in homes with highly contaminated yards, and who ingest soil from the highest contaminated area in the yard three or four times in a week, the estimated dose in these children might produce serious health effects. For instance, the estimated weekly exposure dose for a 1-year-old soil-pica child who lives at the property with the highest average arsenic level is estimated to range up to 0.6 mg/kg/day depending on how much soil the child ingests (see Appendix H, Table H-1). This dose is dangerously close to the dose level of 2 mg/kg/day shown in a report by Armstrong et al. that produced serious health effects (Armstrong et al. 1984, ATSDR 2000.) Some factors about arsenic toxicity, however, add some uncertainty to this conclusion. First, arsenic toxicity may be less if soil-pica behavior occurs every other day rather than several days in a row, because exposure every other day may allow the body time to recuperate. In addition, eating large amounts of soil or having food in the stomach may reduce how much and how fast arsenic is absorbed across the gut, which might reduce its harmful effects.
Based on ATSDR's estimate of arsenic exposure over a week, around 45 of the properties sampled so far in the VBI70 study area have average arsenic levels in soil that might produce serious effects in habitual soil-pica children. ATSDR considers average arsenic levels greater than about 270 ppm to be a concern for habitual soil-pica children. Since EPA has cleaned up these 45 properties, they are no longer a risk to the preschool children who live there.
As pointed out previously, however, about a thousand residential properties have not been sampled in the VBI70 study area and some of these properties will have dangerous levels of arsenic in soil. About 30 of these 1,000 unsampled properties might have arsenic levels that could produce very serious effects in habitual soil-pica children.
It is extremely important that residents and health professionals interpret ATSDR's findings in the proper context. Although there is a potential for adverse health effects to occur among some soil-pica children who are exposed to contaminated soils in the VBI70 study area, members of the VBI70 community and health professionals should note the following.
Possible non-cancerous health effects in adults
Soil exposure for adults differs from soil exposure for children because adults have the potential for being exposed to low levels of arsenic over a much longer time frame and adults ingest smaller amounts of soil. ATSDR compared the estimated amount of arsenic exposure (or dose) to a "health guideline" dose developed specifically for many years of exposure. The health guideline dose is an exposure level below which you would not expect to find harmful non-cancer health effects. For long-term ingestion exposures to arsenic, both ATSDR and EPA use the same health guideline value. ATSDR calls its value a chronic Minimal Risk Level (MRL), and EPA calls its value a chronic Reference Dose (RfD). The chronic MRL and chronic RfD for arsenic is 0.0003 mg arsenic per kilogram body weight per day or 0.0003 mg/kg/day. It means that if people are exposed to less than 0.0003 mg/kg/day for many years, then non-cancerous harmful effects are unlikely. It is important to note that the chronic MRL and the chronic RfD apply to non-cancerous effects only and are not used to determine whether or not people could develop cancer (ATSDR 2000).
Adults ingest up to maybe 100 mg of soil each day, probably from inadvertent hand-to-mouth activity or from working in the yard. Using 30 mg or 100 mg a day for soil ingestion, the average level of arsenic in people's properties, and a bioavailability of 60 percent, ATSDR estimated the range of arsenic exposures for adults who live in the VBI70 study area. At about 45 properties with average arsenic levels above 270 ppm, the amount of arsenic exposure in adults is greater than the chronic MRL and chronic RfD for arsenic. However, the estimated arsenic exposure in adults is still well below the level where harmful health effects were observed in human studies (ATSDR 2000). Therefore, ATSDR concludes that it is unlikely that adults at any of the properties in the VBI70 study area sampled during Phase III will experience non-cancerous harmful effects from arsenic in soil.
Possible harmful effects in workers
As mentioned previously, some workers in the VBI70 study area might come into contact with contaminated soils should their work activities involved close contact with soil. For instance, contractors and utility workers might work on job sites that require digging. If these workers were to get arsenic-contaminated soils on their hands, and then engage in hand-to-mouth activity, they too could be exposed to arsenic. It is uncertain how much soil workers typically swallow but a reasonable estimate might be that workers occasionally ingest up to 500 mg. In most cases, this exposure is not likely to cause harmful effects. However, should workers ingest 500 mg or more of soil that contains high amounts of arsenic (for instance, 10,000 ppm arsenic) they might experience symptoms similar to those described for children with soil-pica behavior.(22) They might experience nausea, vomiting, diarrhea, facial edema, and headaches.
According to EPA and the U.S. Department of Health and Human Services, arsenic is known to cause cancer in people. This judgment is based on convincing evidence from many studies of people who were exposed to either arsenic-contaminated drinking water, arsenical medications, or arsenic-contaminated air in the workplace. The studies provide evidence of arsenic causing cancer for various exposure durations, ranging from a few years to an entire lifetime (ATSDR 2000). Of the different types of cancer from oral exposure, skin cancer–namely, squamous cell carcinoma and basal cell carcinoma–and other types of cancer, including cancer of the lungs, bladder, kidney, liver are a concern.
There are different ways to evaluate whether the arsenic soil levels at VBI70 have the potential to cause cancer among exposed individuals. One way is to compare the exposure doses for the VBI70 study area to the exposure doses that have been reported in the literature to increase cancer in humans. Using this approach, people who live all or most of their life in homes in the VBI70 study area with the most highly contaminated yards and who are in the highest bracket for soil ingestion have estimated exposure levels to arsenic that are similar to exposure levels that have been shown in human studies to cause cancer (ATSDR 2000.) This conclusion applies to about 40 properties with average arsenic levels above 300 ppm and is based on the following assumptions:(23)
It is important to realize that ATSDR is not proposing 300 ppm as a clean-up number or action level but is emphasizing the seriousness of potential arsenic exposure levels at many of the more highly contaminated properties.
Another way to evaluate the cancer-causing potential from arsenic in soil is to use mathematical estimates of cancer risk based on estimated arsenic exposure over many years. EPA typically uses this approach to estimate a potential increased risk of cancer from estimated exposure doses. A key parameter in this calculation is the cancer slope factor, which, for arsenic, was derived from arsenic exposures and skin cancer cases reported in the Taiwan study (Tseng et al. 1968, ATSDR 2000.) Applying this mathematical method to the VBI70 study area, ATSDR estimated doses for exposure scenarios ranging from 30 to 70 years, 40 and 60 percent bioavailability, people with average soil intake, and people with high soil intake. Based on these estimated doses, the mathematical model suggests that a significant potential increase in cancer risk might exist for long-time residents at many of the properties that were sampled as part of Phase III.
For people with high soil intake, the cancer risk at the more highly contaminated properties ranges from about 3 extra cases per every 10,000 people exposed to about 20 extra cases for every 10,000 people exposed for a lifetime to arsenic in soil.
When applying this cancer risk to the VBI70 study area, which contains 13,000 people, it is wrong to conclude that one might expect to see 20 or so arsenic-induced cancers for the 13,000 people who live in the VBI70 study area. The reason for this is that most properties in the VBI70 site are not contaminated with arsenic; therefore, most of the people are not exposed to high arsenic levels. In addition, the estimated number of cancers is based on a relatively small group of people in the high soil intake bracket. To put in perspective the cancer risk of 3 to 20 extra cases of cancer for every 10,000 people exposed, one needs to realize the following points.
ATSDR notes also that there is some uncertainty in the mathematical estimate of cancer risk for several reasons:
In addition to the uncertainties listed above, some scientists believe that the mathematical model is inherently flawed. Specifically, they believe that exposures to small amounts of arsenic are safe if they are lower than a "threshold dose" for cancer. These scientists suggest that exposure to small amounts of arsenic might not cause cancer (Stöhrer 1991; Abernathy et al. 1996).
In support of the cancer-causing potential for arsenic in the environment, the National Research Council recently concluded that there is little evidence to support a threshold for arsenic carcinogenesis and noted that nutritional status and arsenic exposure from other sources in the Taiwanese studies would have only modest impact on cancer risk estimates derived from using the Taiwanese data. It should be noted that cancer studies from other countries, such as Chile, India, and Bangledesh support the cancer estimates derived from the Taiwanese studies.
Despite these uncertainties, the two different approaches for evaluating whether highly contaminated arsenic soil levels in the VBI70 study area might cause cancer yield similar conclusions that arsenic levels in soil at some properties are a public health concern for cancer. The common finding is that people who live in homes with the most highly contaminated yards in the VBI70 study area for many decades might be exposed to arsenic at levels that increase their risk of cancer.
Homeowners who refused soil clean up
As mentioned earlier in this report, the owners of six properties in the VBI70 study refused to allow EPA access to clean up arsenic-contaminated soil at their homes. The soil arsenic levels at these properties could cause harmful effects in some soil-pica children, preschool and elementary school children who live at these homes or who visit them and have typical soil intakes.
ATSDR plans to talk to these residents to inform them of the health risks involved with soil arsenic contamination in hopes of convincing them to allow EPA access to clean up their yards. ATSDR also plans to talk to EPA, state, and local agencies about a notification system for these properties.
Arsenic levels in the Northeast Park Hill neighborhood
High levels of arsenic have been found in some yards in the Northeast Park Hill neighborhood, a residential area east of the VBI70 study area that is not part of the NPL site. The limited number of soil samples from the properties sampled do not allow ATSDR to evaluate long-term exposure to arsenic. However, the results show that some properties are likely to have significant arsenic contamination. For instance, the four samples from one property on Glencoe all had significantly elevated arsenic. In addition, high levels of arsenic in soil were found in some properties that could cause harmful effects in some children with soil-pica behavior. It is difficult to be certain about the degree of the health threat for soil-pica children in the properties sampled because the limited number of samples do not allow ATSDR to know the true maximum arsenic level. The high frequency of significantly elevated arsenic levels in the 36 properties sampled leads ATSDR to believe that many homes in the Northeast Park Hill neighborhood have areas in their yards with high levels of arsenic contamination that could be harmful to children, especially children with soil-pica behavior.
Possible Health Effects from Exposures to Lead
ATSDR also evaluated whether residents of the VBI70 study area were or are being exposed to lead in soils at levels that might be associated with adverse health effects, both for cancer and non-cancer effects. Regarding cancer effects, the weight-of-evidence from a large number of studies of lead exposure in humans has yet to establish a clear link between lead and cancer. Given the vast amount of research conducted on lead-related health effects, this lack of evidence suggests that lead is a very weak carcinogen in humans, if at all. Therefore, exposures to lead in the soils in the VBI70 study area likely do not cause additional cancers among residents. Further, the many studies on the toxicity of lead have shown that children are most susceptible to adverse health effects following exposures, and environmental exposures among adults generally do not result in as serious effects. As a result, the remainder of this section focuses on non-cancer effects that might occur in children following exposures to lead.
Residents of the VBI70 study area can be exposed to lead in soil in the same manner that they can be exposed to arsenic in soil–that is through ingestion by hand to mouth activity. As noted earlier, preschool children have the greatest amount of exposure because they frequently touch soil and touch their mouths. In addition, soil-pica behavior can also result in excessive exposure to lead. Other sources of lead could also exist in the VBI70 study area that might add to the lead exposure that comes from contaminated soil. These other sources include lead-glazed pottery as well as lead-based paint in homes, especially since roughly 80% of homes built in the U.S. before 1978 are believed to still contain some lead-based paint (CDC 1985, 1991). Older homes not only are more likely to have lead-based paint, but also are more likely to have higher concentrations of lead in their paint. Housing built before 1950 that has not been resurfaced poses the greatest risk for children being exposed to lead from paint (CDC 1985, 1991). In the VBI70 site, about 60% of the homes were built before 1950, while about 80% of the homes were built before 1978, the year lead-based paints were banned for home use (see Appendix D, Table D-1 for more details.) In addition, children can also be exposed to lead through their diets, eating food from lead-containing ceramics, using certain traditional medical remedies, and from some parents' occupation and hobbies (CDC 1985, 1991). Therefore many sources of lead often exists in a child's environment, including lead-contaminated soils.
Different investigators have found widely varying relationships between soil and dust lead levels and children's blood lead levels. Based on a review of other investigators, the Centers for Disease Control and Prevention (CDC) reports that blood lead levels generally rise 3 to 7 micrograms per deciliter (µg/dL) for each increase of 1,000 ppm of lead in soil or dust (CDC 1991, EPA 1986, Bornschein et al. 1986, ATSDR 1988). The CDC has established a blood lead level of 10 µg/dL (10 micrograms of lead per deciliter of blood) as a level of concern.(24) CDC established this value after evaluating a large number of rigorous epidemiologic and experimental studies. In particular, recent human studies have provided new evidence about the association between low-level lead exposure and child development (CDC 1991). CDC states that blood lead levels that exceed 10 µg/dL are associated with decreased intelligence and impaired neurobehavioral development. Many other effects begin at these low blood lead levels, including decreased stature or growth, decreased hearing, and decreased ability to maintain a steady posture, and become more pronounced at higher blood lead levels. Lead's impairment of the synthesis of vitamin D is detectable at blood lead levels of 10 to 15 µg/dL.
The concern at the VBI70 site is what contribution lead in soil will make to a child's blood lead level that is already affected by other sources of lead. Because children's play habits and hand-to-mouth activity vary, the contribution that lead in soil makes to a child's blood lead level most likely varies. This variation makes it very difficult to decide for an individual child how much lead in soil is actually getting into a child's blood. Therefore, lead levels in soil must be evaluated in a more general sense.
EPA has developed a mathematical model that uses the average soil lead levels in a property to predict the percentage of children with blood lead levels above the Centers for Disease Control and Prevention's (CDC) level of concern of 10 micrograms lead per deciliter of blood (µg/dL). For the VBI70 site, EPA's model predicts a range of soil lead levels that could result in more than 5% of the children having blood lead levels greater than 10 µg/dL. The range of soil lead levels predicted by the model vary because EPA varied certain input parameters in the model (specifically, the geometric standard deviation and dietary lead intake). The model predicted that soil lead levels ranging from as little as 208 ppm to as much as 540 ppm as being a concern for increasing blood lead levels in children depending upon which input parameters most accurately predict blood lead levels.(25) It should be noted that 78 properties have average lead levels in soil higher than 540 ppm while about 1,350 properties have average soil lead levels higher than 208 ppm.
Site-specific conditions, such as, amount of bare soil, children's play areas, chemical form of lead, how much lead crosses the gut, and particle size could affect blood lead levels and the possibility of harmful effects occurring. It should be noted that EPA cleaned up four properties in 1998 with average lead levels greater than 2,000 ppm.
The elevated levels of lead in soil in some properties in the VBI70 site along with lead from other sources increases the risk in some preschool children for having increased levels of lead in their blood. At blood lead levels slightly above 10 µg/dL the following health effects might occur in affected children:
These lead-related effects are documented in several population studies that investigated the harmful effects of lead (e.g., ATSDR 1999; CDC 1991). The effects are difficult to identify in individuals with blood lead levels between 10 and 20 µg/dL because the effects are subtle changes. The effects can be detected, however, when large groups of children are studied.
Since limited blood lead measurements have been conducted on children who live at the VBI70 site, the exact extent to which soil contamination might have contributed to their blood lead levels or caused harmful effects is not known. In summer 2000, the Colorado Department of Public Health and Environment (CDPHE) offered voluntary blood lead testing at several locations in the VBI70 site as part of their lead poisoning prevention program. This program targets children who are not covered by Medicaid. In addition, as recent as September 25, 2000, at Saint Martin's Plaza and October 3, 2000, at Harrington Elementary School, CDPHE offered lead testing for children. Of the 86 children that participated, 8 had blood lead levels that exceeded the CDC's level of concern of 10 µg/dL with the highest level detected being 18 µg/dL. The age of the children ranged from 7 months to 6 years. Finding this many blood lead levels above CDC's 10 µg/dL shows that a significant blood lead concern is likely to exist for children living in the VBI70 study area.
In evaluating public health issues concerning children and lead, it is important to remember that children get exposed to lead from many sources. In addition to lead coming from soil, children also get exposed to lead from other sources. Here are a few examples:
CDPHE has a blood lead program that tests children for blood lead. For more information about CDPHE's blood lead program, contact Ms. Mishelle Macias at 303-692-2622. In addition, the Denver Department of Environmental Health (DEH) within the City and County of Denver is responsible for responding to lead issues. DEH's program is managed by Mr. Gene Hook, who can be contacted at 720-865-5452. DEH follows CDC guidelines, and when a child with elevated blood lead is referred, DEH will conduct an environmental investigation to identify potential sources of lead. Typically, the investigation includes collecting environmental samples from the home environment and administering a questionnaire designed to identify lead sources. DEH also provides the family with information about the health effects of lead, ways to prevent exposure to lead, proper nutrition, access to other relevant services, and the need for follow up blood tests.
CDC states that blood lead levels below 10 µg/dL are not considered to indicate lead poisoning. CDC considers children with blood lead levels between 10 and 14 µg/dL to be in a border zone. CDC does not recommend a home inspection when children are found at these levels because CDC states that it is unlikely that a single predominant source of lead exposure can be found for most of these children. CDC states, however, that it is prudent to try and decrease exposure to lead with some simple instructions and to conduct a follow-up blood lead test in 3 months. CDC states that the adverse effects of blood lead levels between 10 and 14 µg/dL are subtle and are not likely to be recognizable or measurable in the individual child (CDC 1991).
CDC states that when children have venous blood lead levels of 15 to 19 µg/dL, careful followup is warranted. A health care provider or appropriate health official should take a careful history to look for sources of lead exposure, and parents should receive guidance about interventions to reduce blood lead levels. CDC states that children with blood lead levels between 15 and 19 µg/dL are at risk for decreases in intelligence of up to several IQ points and other subtle effects (CDC 1991).
Possible Interactive Effects from Exposure to Arsenic and Lead
ATSDR has released for public comment a report that evaluates the possibility of interactive effects from exposure to several metals, including arsenic and lead. This report is called the Interaction Profile for Arsenic, Cadmium, Chromium and Lead.
The report concludes that if the combined exposure to arsenic and lead are high enough evidence suggests that there might be a greater potential for causing neurological effects than exposure to arsenic or lead alone (ATSDR 2002). A study in children suggests that exposure to lead increases scores for maladaptive classroom behavior with higher scores for maladaptive behavior in children with lead and arsenic exposure. In addition, the study suggests that exposure to arsenic decreases reading and spelling performance and is further decreased in children with arsenic and lead exposure (Marlowe 1985, Moon 1985).
Several factors need to be considered when understanding the conclusions from the Marlowe and Moon study. Because of the limited number of studies in humans it should be emphasized that the conclusion about possible interactive effects between arsenic and lead is only suggestive and not definite (ATSDR 2002). In addition, this study used the level of arsenic and lead in children's hair as an indicator exposure. Hair levels may indicate contact with a chemical rather than ingestion of a chemical. For instance, children might come into contact with lead and arsenic in dirt. The lead and arsenic can be transferred directly to the hair from dirt without actually exposing the child. Therefore, hair levels may not indicate actual intake of lead or arsenic.
When conducting human studies, scientists know to take into account certain variables that might affect a child's performance. For instance, Marlowe and Moon controlled for variables such as the parents' age at their child's birth, parents' occupation and education, father's social class, father's presence in the home, child's birth weight, and child's length of hospitalization. The authors, however, did not control for the child's care-giving environment and the child's nutritional status. Not controlling for these two important variables casts some doubt on the conclusions. For these reasons, the conclusion about possible interactive effects between arsenic and lead are suggestive (ATSDR 2002). Another drawback also exists when trying to use the conclusions about possible adverse effects based on hair levels. In the case of children living in the VBI70 area, it is not possible to estimate their dose for arsenic and lead from ingesting soil and decide if the effects reported by Marlowe and Moon are possible.
DISCUSSION OF COMMUNITY CONCERNS AND QUESTIONS
ATSDR staff members met with community representatives many times and with residents at an availability session held in the VBI70 study area where they had the opportunity to talk with ATSDR employees, either one-on-one or in small groups. Residents asked ATSDR to address several health and environmental questions. These questions are listed below with ATSDR's responses (shown in italics). In some cases, questions were referred to the appropriate federal, state, or local agency for a response.
The VBI70 health team developed a fact sheet that responds to this question (see Appendix I). In general, residents can take the following simple steps to reduce exposure to contaminants in soil:
No evidence exists to show that African-American or Hispanic communities are more or less sensitive than other groups to arsenic and lead because of their genetic make-up.
Some factors that might increase someone's sensitivity to arsenic are listed here:
In addition to the issue that some people are more sensitive to the effects of arsenic as previously described, some difference exists in the distribution of contamination in the neighborhoods. Specifically, more homes in Elyria, a predominantly Hispanic neighborhood, and Cole, a predominantly African-American neighborhood, have yards with elevated levels of lead in soil compared to Swansea and Clayton. This conclusion is shown in the lead distribution maps that appear in Figures 10 and 11.
One possible explanation for more frequent lead contamination in Elyria, Cole, and Southwest Globeville is that fallout from one of several nearby smelters has raised lead levels in surface soil. Another possible explanation is that the homes in the western portion of the site are older and therefore more likely to have lead paint on the exterior. The implication is that years of weathering and chipping has contaminated the yards. This explanation seems unlikely since the percentage of older homes (for instance, homes built before 1950 when high amounts of lead were commonly added to paints) is very similar in Elyria, Cole, and Southwest Globeville compared to Swansea and Clayton (see Appendix D, Table D-1.)
The community representatives asked that government officials be aware that they might not understand the technical terms and government jargon that is frequently used when talking about the VBI70 site. ATSDR staff members and other government officials worked with community members during the health team meetings to limit the use of technical terms. When technical terms had to be used, they were defined for the team members. ATSDR staff members had several meetings with community representatives to help them understand the technical terms and the process used to make public health decisions. A glossary of environmental and health terms is provided in Appendix J.
Agency members of the VBI70 health team agreed to help community representatives with technical issues and agreed that community representatives should be an integral part of planning community meetings. Further, Agency members agreed to help community representatives develop and present messages to the community. For example, when ATSDR released its fact sheet on gardening in the VBI70 study area, ATSDR staff members worked with community members to develop the fact sheet and to set up community meetings for the residents to answer questions about gardening. ATSDR also worked with community representatives as they wrote and used parts of the fact sheet in the newsletter for Swansea and Elyria.
Ms. Barbara O'Grady, the site lead for CDPHE, said that CDPHE will respond to this issue. Ms. O'Grady said that Mr. Glenn Malloy (303-692-3445) or Mr. Peter Laux (303-692-3455) with CDPHE's Solid Waste Unit might have answers about the landfill. Also, Ms. Celia VanDerLoop (City and County of Denver) said that she may also have information about landfills in the neighborhoods.
During ATSDR's investigation, ASARCO officials hosted a site tour of its Globe facility to allow government officials and community representatives to become familiar with the facility's operations. In addition, ATSDR learned from ASARCO representatives that the facility currently produces bismuth products,(26) litharge,(27) highly purified lead, and tellurium.(28) Small amounts of highly purified "specialty metals" are also produced. Specialty metals produced during the last year include cadmium telluride, cadmium sulfide, lead telluride, zinc telluride, and high purity copper cylinders. ASARCO did not provide information to ATSDR about what is emitted by the facility.
No data are available to confirm whether non-cancerous effects mentioned are greater than expected for this part of Denver. Decisions about whether or not to determine cancer and non-cancerous disease rates for the VBI70 studyarea will be made at a later date.
The Cross Community Coalition has applied for a grant from the federal National Institute of Environmental Health Sciences to investigate the status of adverse health effects in the community. Information from this investigation will be useful in answering some of the previous questions.
The CDPHE has a cooperative agreement with ATSDR to conduct health education in the community. The agencies are working with community representatives on these issues. For instance, a letter to physicians and other health care providers is being drafted to inform them of the VBI70 site and its associated hazards. As part of ATSDR's environmental health interventions project, ATSDR staff members will be working with a local clinic and with community representatives to educate people about the adverse health effects from arsenic and lead. In addition, when the public health assessment is released, ATSDR staff members will hold public meetings to talk to residents about the report and to answer their questions as well as holding a press release and talking with news media. As the agencies continue to work together with community representatives, other activities may also be started.
Since CDPHE developed the 70 ppm cadmium clean-up number for the Globeville ASARCO site, ATSDR has referred this question to CDPHE staff members.
In 1999, EPA responded to these questions during its monthly meetings with the community representatives.
DISCUSSION OF HEALTH OUTCOME DATA
Completed Medical testing
During its 1998 Phase II investigation, EPA identified 21 properties that required immediate clean-up because soils at these properties had either high levels of arsenic (greater than 450 ppm) or high levels of lead (greater than 2,000 ppm). To characterize potential exposures, EPA offered to collect and analyze blood, hair, and urine samples from the residents of these properties, at no cost to the residents. Overall, EPA contacted 69 residents from 17 of the 21 properties of concern, but only 15 residents from six properties volunteered to participate in EPA's biological survey. These 15 residents included nine adults, five children or teenagers, and only one preschool child. This breakdown of the surveyed population is important, since the group most likely to be exposed, preschool children, were not tested.
EPA performed three types of measurements on the biological samples that were collected from the 15 residents. A summary of the survey's findings follows:
Arsenic in urine
EPA reported that no arsenic was detected in the urine of people tested, and the detection limits in this study ranged from as low as 10 micrograms per liter (µg/L) to greater than 50 µg/L. Of the urine samples collected during the survey, five had undesirably high detection limits–greater than 50 µg/L–which limits the usefulness of these samples. The five participants refused to provide additional samples. The results of the remaining urine samples showed that the residents did not have excessive exposure to arsenic at the time the survey was conducted. ATSDR does not believe, however, that this finding means that levels of arsenic in the soil at the properties were safe. The reasons for reviewing the conclusion with caution follow:
Arsenic in hair
EPA also measured arsenic levels in hair samples from the 15 participants. In general, arsenic can become part of human hair by different processes. For example, arsenic that is absorbed into the body can become part of newly made hair as it grows, thus arsenic levels in parts of the hair represent exposure over the growth period of the hair. In addition, arsenic in the external environment can bind directly to hair upon contact. For instance, arsenic in sweat can become bound to hair and arsenic in dusts in the environment can settle onto hair and be transferred directly to hair. When measuring hair arsenic levels, however, it is impossible to know how the arsenic got there, which complicates efforts to interpret the meaning of arsenic levels in human hair. In EPA's survey, only one hair sample had detectable levels of arsenic, and its concentration was 0.41 ppm. The remaining 14 hair samples did not have detectable levels of arsenic. Two of these samples had undesirably high detection limits, but the subjects refused to provide additional samples. Overall, the hair samples suggest that elevated exposures of arsenic did not occur among the subjects, but, for the reasons listed previously, these findings are not convincing.
Lead in blood
EPA also measured blood lead levels in some residents. The concentrations of lead in the 15 blood samples ranged from 1 to 4 µg/dL (deciliter)(29), and the geometric mean concentration for the 15 samples was 2.2 µg/dL. For reference, a national survey found that the geometric mean concentration for blood lead was 2.8 µg/dL for people aged 1 to 74 years (CDC 1991, ATSDR 1999). Moreover, all of the blood lead levels measured by EPA are lower than 10 µg/dL–the level that the Centers for Disease Control and Prevention (CDC) has established as a guideline for deciding when actions should be taken to reduce blood lead levels. When levels are lower than 10 µg/dL, CDC recommends that no actions be taken. Therefore, the blood lead results from EPA's biological sampling survey shows that excessive exposure to lead did not occur at the time of testing. However, for the reasons cited previously, ATSDR does not think these results can be used to draw conclusions about the safety of soil lead levels at the VBI70 site.
In summer 2000, the Colorado Department of Public Health and Environment offered voluntary blood lead testing at several locations in the VBI70 site as part of their lead poisoning prevention program. As recent as September 25, 2000, at Saint Martin's Plaza and October 3, 2000, at Harrington Elementary School, CDPHE offered lead testing for children. Of the 86 children that participated, 8 had blood lead levels that exceeded the Centers for Disease Control and Prevention's level of concern of 10 micrograms lead per deciliter (10 µg/deciliter). The age of the children ranged from 7 months to 6 years.
The CDPHE did not find a relationship between blood lead results and lead levels in soil but too few children were tested to conclude whether or not soil lead levels are contributing to blood lead levels. For more information about CDPHE's blood lead program, contact Ms. Mishelle Macias at 303-692-2622.
CDC states that blood lead levels below 10 µg/dL are not considered to indicate lead poisoning. CDC considers children with blood lead levels between 10 and 14 µg/dL to be in a border zone. Therefore, many of these children may have blood lead levels that are below 10 µg/dL. CDC does not recommend a home inspection when children are found at these levels because CDC states that it is unlikely that a single predominant source of lead exposure can be found for most of these children. CDC states, however, that it is prudent to try and decrease exposure to lead with some simple instructions and to conduct a follow-up blood lead test in 3 months. CDC states that the adverse effects of blood lead levels between 10 and 14 µg/dL are subtle and are not likely to be recognizable or measurable in the individual child (CDC 1991).
CDC states that when children have venous blood lead levels of 15 to 19 µg/dL, careful followup is warranted. A health care provider or appropriate health official should take a careful history to look for sources of lead exposure, and parents should receive guidance about interventions to reduce blood lead levels. CDC states that children with blood lead levels between 15 and 19 µg/dL are at risk for decreases in IQ of up to several IQ points and other subtle effects (CDC 1991).
On-going medical tests
EPA has offered urine arsenic, hair arsenic, and blood lead testing to anyone in the VBI70 study whose property was tested as part of Phase III. To be tested, residents were given a voucher that allowed them to go to the Centra Clinic in Globeville for testing. The EPA has informed ATSDR that a small number of people have been tested, but they have not shared those data with ATSDR because of confidentiality issues.
ATSDR is working with CDPHE and the University of Colorado to develop a plan to collect biological samples from residents of the VBI70 study area. In addition, ATSDR is considering ways to identify soil-pica children and ways to access their health.
DISCUSSION OF OTHER ACTIVITIES
ATSDR and EPA Efforts to Evaluate Past Human Studies and Arsenic Toxicity
When evaluating soil arsenic levels at the VBI70 site, ATSDR raised concerns about acute arsenic exposure (exposures for just one time or for a few days) in children with soil-pica behavior. Since EPA did have a health guideline for evaluating this exposure scenario, EPA proposed in October 1999 that the two agencies jointly evaluate human studies for acute (less than two weeks) and subchronic (two weeks to 7 years) exposures to arsenic. The purpose of this effort is to identify the most appropriate human studies for evaluating acute and subchronic exposures to arsenic. The workgroup has completed its task and EPA is developing a report that summarizes the findings. The purpose of this effort is intended to ensure a consistent approach between ATSDR and EPA at the VBI70 site and at other sites where arsenic is a contaminant of concern from acute and subchronic exposures.
Health Education and Promotion at the VBI70 Site
When investigating hazardous waste sites, ATSDR often recommends and conducts health education and community involvement activities prior to the release of a public health assessment and other site-related reports. In the case of VBI70, ATSDR is working cooperatively with CDPHE to conduct important health education activities. Some activities have already been completed and additional activities are planned to educate health care providers.
As previously noted, an important health education activity for the site started with the ATSDR-CDPHE joint evaluation of the safety of gardening in the VBI70 study area. Based on this evaluation, the health team members developed two fact sheets describing safe gardening practices and outlining the results from the evaluation (see Appendices E and F). The fact sheets were distributed in both English and Spanish to residents around the VBI70 site and were printed in a community newsletter, which was sent to approximately 2200 residents. Additionally, the group held two public availability sessions at the Herrington Elementary School and the Swansea Community Center in April 1999. During these meetings, residents were able to ask public health specialists questions regarding the safety of gardening and to receive gardening tips from a horticulturist from the University of Colorado. Additionally, ATSDR has prepared and distributed an information sheet that outlines steps residents can take to protect their health and prevent exposure to contaminants in soil (see Appendix I). Ongoing activities, such as contacting local health care providers to introduce them to the VBI70 site, are in the early stages of development.
ATSDR's Child Health Initiative
To ensure that the health of the nation's children is protected, ATSDR implemented an initiative requiring that health assessments determine whether or not children are being exposed to site-related hazardous waste and whether or not the health of children might be affected.
This public health assessment reflects ATSDR's concern about protecting children's health from toxic chemicals in the environment. Specifically, whenever soil is a pathway of concern, as it is at the VBI70 site, children will have greater exposure to contaminants in soil than adults. As a result, a major focus of ATSDR's investigation at the VBI70 site was children's exposure to arsenic and lead in soil, and the potential health effects associated with this exposure. As noted throughout this report, evaluating exposures to children with soil-pica behavior had a strong influence on ATSDR's public health decisions. By examining high-end exposures among children in the VBI70 study area as well as exposures among children with soil-pica behavior, ATSDR has conducted a complete assessment of how contamination in the VBI70 study area might affect children's health.
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