PETITIONED PUBLIC HEALTH ASSESSMENT
PHELPS DODGE CORP DOUGLAS REDUCTION WORKS
DOUGLAS, COCHISE COUNTY, ARIZONA
The tables in Appendix B list contaminants found in each medium on and near the site. Those contaminants are evaluated in subsequent sections of this public health assessment to help determine whether exposure to them has public health significance. ATSDR selects and discusses contaminants using certain factors: concentrations on and off site; the quality of the field and laboratory data sample design; comparison of on- and off-site concentrations to public health assessment comparison values for noncancer and cancer endpoints, and community health concerns.
The listing of a contaminant in the tables does not mean that it will cause adverse health effects if a person is exposed to the specified concentrations. Contaminants included in the tables are further evaluated in this public health assessment. The potential for adverse health effects resulting from exposure to contaminants of concern is discussed in the Public Health Implications section of this public health assessment.
Comparison values for ATSDR public health assessments are contaminant concentrations in specific media used to select contaminants for further evaluation. Appendix C describes comparison values used in this public health assessment.
In 1989, ADHS evaluated the on-site slag pile to determine if the wastes were safe to use for paving roads. Samples from the pile were analyzed for copper and lead only. Copper was detected at a level about three times higher than the normal copper-in-soil level for south-eastern Arizona. Lead was found at levels similar to background levels. The material was not classified as a hazardous material (under the Resource Conservation and Recovery Act), and its potential for leaching heavy metals into Whitewater Draw or groundwater was low (see Table 1, Appendix B)(4).
Phelps-Dodge conducted on-site soil testing during copper recovery activities in 1989. Soils were tested for heavy metals (in addition to copper). Copper, lead, and arsenic were all found above comparison values (see Table 1B in Appendix B). As mentioned earlier, these soils were subsequently removed to levels below ADHS guidelines by 1991 (45). In 1994,ADEQ reported that there may be soils on site that were still contaminated. In 1995, on-site soil testing by EPA found arsenic, cadmium, chromium, lead and mercury to be above comparison values (see Table 1C in Appendix B).
Reports by workers that cyanide wastes were buried on site in drums during removal operations triggered a U.S. Environmental Protection Agency (EPA) investigation in 1990. Workers identified suspected waste burial areas for EPA and state environmental staff; EPA staff excavated the areas. No cyanide or other hazardous materials were found on site (4, 13).
EPA conducted on site groundwater monitoring for heavy metals in 1989 as part of an ongoing site investigation. EPA utilized four on site wells that were in existence at the time (these wells have been abandoned, filled with cement, and sealed so that further sampling of them is not possible). Arsenic exceeded comparison values for drinking water (see Table 2A in Appendix B) (45).
EPA conducted on site surface water monitoring for heavy metals in 1995 as part of an ongoing site investigation. The samples, which were collected during the rainy season, were taken from surface run-off water that accumulated and formed puddles. Arsenic and lead exceeded comparison values for drinking water (see Table 2B in Appendix B).
In 1990, the state OSHA unit monitored for asbestos in asbestos removal areas during site remediation (5). At the time of inspection, the employer had completed 2,710 airborne asbestos samples, including an estimated 1,800 personal breathing zone samples and 900 area samples. Asbestos levels in several of the samples exceeded OSHA standards. OSHA reports that respiratory protection had been provided at the time of testing (see Table 3 in Appendix B).
Surface Soil (less than 3 inches)
In 1985, ADHS took 52 surface soil samples from a widespread area in Douglas and analyzed them for lead only. Lead levels in the soil were highly variable, ranging from 50 to 1,170 milligrams lead per kilogram (mg/kg) soil. Average soil lead levels for Douglas and Pirtleville were 254 mg/kg and 341 mg/kg, respectively; the highest levels were found in Pirtleville (see Table 4, Appendix B)(4).
EPA took seven off-site surface soil samples downwind from the Phelps-Dodge site in 1989. Distance intervals of the sample locations ranged from about one to six miles from the site. Lead, arsenic, and copper levels exceeded comparison values. Samples taken at points greater than about 2.5 miles from the site were similar to background levels for lead, arsenic, and copper (see Table 4 in Appendix B) (45).
Subsurface Soil (3-12 inches)
In 1985, two subsurface soil samples were taken (at 3 and 5 inches); both had lead levels below 250 mg/kg. Soil below 5 inches was not tested.
Groundwater - Municipal Well
ADEQ tested city well no. 6 in May 1984 for metals; arsenic and lead slightly exceeded comparison values. When all city water wells were tested in 1980, all metals were below comparison values (1). The municipal well field and pumping station are about a half mile north of the former smelter (see Table 5, Appendix B)(1, 7, 9).
ADEQ tested city wells in Agua Prieta, Sonora, Mexico, in 1988 and 1989. The wells lie less than a mile from the former smelter site. Results in 1988 found arsenic levels between 0.023 and 0.024 milligrams per liter (mg/L). In 1989, arsenic only slightly exceeded the detection limit of 0.01 mg/L. Lead was not detected in either 1988 or 1989 (1).
Between 1987 and 1991, ADEQ monitored Whitewater Draw for contamination with heavy metals. Heavy metals exceeded comparison values off site and downstream from the smelter (6). It should be noted that the only comparison values available for surface water analysis are those used for drinking water, thus, the comparison values are very conservative. The public health implications for surface water exposure will be further addressed in the Public Health Implications Section (see Table 6, Appendix B).
ATSDR found no information on sediment contamination.
Between 1970 and 1987, ADEQ monitored off-site ambient air for metals, benzene, and criteria pollutants (see Appendix C for a list of criteria pollutants). Maximum levels found in ambient air during the monitoring period are shown in Table 7, Appendix B (3). Arsenic, benzene, cadmium, lead, inhalable particulates (PM10), and sulfur dioxide exceeded their respective comparison values. Mean PM10 levels have consistently exceeded the NAAQS in the past, even after the smelter had closed (see Figure 2 in Appendix A) (45). Particulate sampling from 1992 averaged 40.2 µg/m3 (19).
EPA conducted ambient air monitoring at one station in Douglas between the fall of 1973 and 1975. The monitoring program focused on sulfur dioxide emissions. Between the summer of 1973 and fall of 1974, EPA made 2416 three-hour observations, four of which exceeded the emission standard for sulfur dioxide (1300 µg/m3). EPA also made 408 24-hour observations in this interval, and 3 exceeded the 24-hour standard (365 µg/m3). The highest three-hour concentration was detected in 1974 and was 10144 µg/m3, about eight times the NAAQS standard. The highest 24-hour concentration was detected between the summer of 1973 and the fall of 1974. This level was 2437 µg/m3, about seven times the NAAQS standard (45).
Results of total suspended particulate (TSP) and sulfur dioxide monitoring by ADEQ between 1970 and 1987 show marked improvement in air quality in Douglas, especially after 1976. The highest annual mean for sulfur dioxide was 140 µg/m3, and was detected in 1976. The lowest was detected in 1987 and was 2 µg/m3. The highest TSP annual mean detected was in 1971 and was 303 µg/m3; the level dropped to 97 µg/m3 in 1987 (see Figures 3 and 4)(3).
Most environmental monitoring (air, soil, surface water, and groundwater) was conducted by ADEQ. QA/QC issues were discussed with ADEQ. On-site air sampling was supervised by the Arizona OSHA unit. Soil sampling in 1985 apparently was completely random; therefore, ATSDR does not have a complete characterization of soil in Douglas. QA/QC of off-site air and all groundwater monitoring was adequate.
Information was available on QA/QC techniques used during blood lead and urine arsenic monitoring. Arsenic levels in urine and lead levels in blood were measured by the ADHS laboratory. Quality assurance samples were submitted to the CDC Reference Laboratory and met established QA/QC standards.
No unusual physical hazards were noted on or off site other than those expected for a typical residential neighborhood (e.g., traffic hazards).
Because Douglas children are known to have elevated blood lead levels (see Table 9, Appendix B), ATSDR investigated potential additional sources of lead exposure. Additional potential sources of lead include lead-glazed ceramic dishware often used by Mexican-Americans (20); azarcon, a Hispanic folk remedy with a high lead content (21); and lead paint in homes (22).
Toxic Chemical Release Inventory
ATSDR searched the EPA Toxic Chemical Release Inventory (TRI) for the site and local area. TRI is an EPA-maintained database containing a summary of toxic chemical releases reported by industries as required by Section 313 of the Emergency Planning and Community Right-To-Know Act of 1986. No toxic releases were reported by facility name (Phelps-Dodge smelter), city (Douglas), or zip code (85607) for the years available on the data base (1987 through 1990).
To determine whether people are or were exposed to contaminants released from the Phelps-Dodge site, ATSDR evaluated the environmental and human components leading to exposure. The pathways analysis consists of five elements:
- source of contamination;
- environmental medium in which the contaminants may be present or from which they may migrate;
- points of human exposure;
- routes of human exposure (e.g., ingestion, inhalation, or dermal absorption); and
- receptor population.
ATSDR considers exposure pathways completed or potential. An exposure pathway is completed when all five elements link the contaminant source to a receptor population; the exposure may have been in the past, may now exist, or may exist in the future. Pathways are potential when people could have been exposed to a contaminant in the past, could be exposed now, or may be exposed in the future. Completed and potential exposure pathways at Phelps-Dodge are shown in (Table 8), Appendix B.
Surface Soil Pathway
People have been exposed in the past, are now exposed, and may be exposed in the future to elevated levels of lead from ingesting contaminated residential soils in Douglas. The most significant points of exposure are those involving direct contact with lead-contaminated soils, such as yards and dirt-covered school playgrounds. In many cases, children in Douglas play directly in the dirt. Adults may be exposed by ingesting small amounts of soil while gardening or during other outdoor activities. Residents who inhale lead-contaminated dust generated by traffic on dirt roads may have additional exposures. In addition, normal climatic conditions of the desert likely result in high levels of lead-contaminated dusts remaining suspended in the air.
In the past, one likely source of elevated soil lead levels in Douglas may have been the former Phelps-Dodge Smelter. Smelting operations resulted in emissions of heavy metal particulate matter, including lead (3). Once released from facility stacks, particulate typically deposit on site, and over widespread areas including any surrounding communities. On-site soils were contaminated with heavy metals in the past; however over 15 million tons of soil were removed between 1987 and 1991. ADEQ reports that there may be soils on site that are still contaminated (47). Because residential areas are about a mile away from the site, on-site soils were and still are an unlikely source of exposure for children.
Residential soils have probably been contaminated with low levels of various heavy metals in the past. Although there is some variability in desert soils, lead is probably the most significant contaminant, given its ability to tightly bind to most soils with virtually no leaching under natural conditions (19). Thus, lead deposited into dust and soil may be a long-term source of lead exposure (23).
Another likely source of lead contamination in Douglas may be lead from auto emissions. Leaded gasoline is available in Mexico and in some gas stations in Arizona, and elevated soil lead levels have been associated with its use. Therefore, emissions from cars fueled with leaded gasoline may contribute to lead contamination of soils. Also, as mentioned previously, Douglas is on the U.S.-Mexican border and is vulnerable to migration of lead-contaminated surface soils from Mexico because winds come from the southeast during part of the day (28), and there is considerable potential for wind erosion of surface soils in desert climates. Dusts originating in Agua Prieta, Douglas' sister city in Mexico, have increased in Douglas in recent years because of the rapid population growth and development of unpaved roads in Agua Prieta. ADEQ reports that 60% of Douglas' dusts originate in Agua Prieta (15). It is not known how much of the dust may be contaminated with lead.
On residential yards and on the school playground in Pirtleville, soil ingestion is an important route of exposure, particularly for children less than 6 years old. Children in Pirtleville may be at highest risk for exposure because soil lead levels found in that area were highest, and, because residential yards and the schoolyard have very little grass, children play directly in the dirt. Children less than six years old are at increased risk of exposure because they are more likely to be outdoors, and they have greater hand-to-mouth activity than older children. Children under 6 typically ingest an estimated 200 milligrams (mg) of soil per day; adults and older children ingest less than 100 mg daily. Children with pica behavior (a tendency to eat nonfood items such as dirt) may ingest as much as 5,000 mg soil per day (12).
Adults with a higher potential of exposure are those who remain at home or in the community during the day and those who garden or frequently work outdoors, because they have more opportunity for contacting contaminated soils. Adults who smoke are at greater risk of exposure because of their increased hand-to-mouth activity.
Soil lead levels measured in Douglas were highly variable, ranging from 50 mg/kg to 1,170 mg/kg. EPA guidance recommends "...400 mg/kg soil lead as a screening level for lead in soil for residential scenarios. Residential areas with soil lead below 400 mg/kg generally require no further action. However, in some special situations, further study is warranted below the screening level. For example...areas of higher than expected human exposure [is a] situation that could require further study." Levels in Pirtleville averaged just under 400 mg/kg, with many samples exceeding 400 mg/kg as found in 1985. EPA also found levels exceeding 400 mg/kg in 1989. Again, Douglas and Agua Prieta have little or no grass cover, unpaved roads, and a dry climate. These factors may result in higher than usual human exposures to soil (46).
Ambient Air Pathway
In the past, smelter emissions also were responsible for ambient air contamination in residential areas of Douglas. Although levels of individual contaminants were low, a number of the substances detected are known or suspected carcinogens. As a result, the ambient air exposure pathway (inhalation) is discussed further in the Public Health Implications section of this public health assessment. Substances detected off site at levels greater than comparison values were arsenic, benzene, cadmium, and manganese. Also in the past, particulate less than 10 microns in diameter (PM10) and elevated levels of sulfur dioxides have been detected (see Table 6, Appendix B).
Between 1970 and 1987, ADEQ and EPA periodically monitored off-site ambient air for concentrations of hazardous substances. Air monitoring for hazardous substances ceased when the smelter closed except for PM10. Of particular concern were arsenic, benzene, PM10 and sulfur dioxide. Arsenic is known to migrate off site and remain in communities near smelters. Arsenic levels, shown in (Table 6), Appendix B, were the highest levels of contaminants detected in Douglas during the air monitoring period. Background levels of arsenic in rural parts of the United States ranged from 0.0 to 0.0001 milligrams per cubic meter (mg/m3) over 1 year (19). The highest level found in the Douglas residential area was 0.000121 mg/m3, a slight elevation above background. One possible explanation for the unexpected low concentrations of arsenic may be the prevailing winds in the area, which are reported to blow towards Mexico in the evening, when emissions would have been greatest (12). Thus, the highest levels of arsenic may have been deposited in ambient air in Mexico rather than in Douglas.
Benzene also was detected in off-site residential ambient air. Unlike the other hazardous substances detected, benzene is not a heavy metal, but a volatile organic compound which is commonly released in car exhaust. Rural background levels of benzene measured in the United States average between 0.001 and 0.017 mg/m3 (19). The highest detected level in Douglas was 0.0108 mg/m3, within the expected background range.
The National Ambient Air Quality Standard (NAAQS) for lead in air is a mean of 0.0015 mg/m3 over a 3-month period. NAAQ standards are established under Section 109 of the Clean Air Act for pollutants that, if present in air, might endanger the public health or welfare. Lead levels detected in residential air at Douglas periodically exceeded the NAAQS; levels were measured as high as 0.0118 mg/m3 (3).
The NAAQS for PM10 is 0.15 mg/m3 over a 24-hour period, not to be exceeded more than once a year. Particulate matter of that size poses a risk to public health because it is "respirable," or small enough to be deposited in lung tissue (32). ADEQ detected PM10 levels as high as 0.221 mg/m3 in residential areas while the smelter was operating (3). The smelter no longer operates, but ADEQ reports that the dust problem from Agua Prieta has worsened over the past few years, in part because of rapid population growth. Average particulate levels also exceeded the NAAQS in the mid eighties, even after the smelter was closed (see Figure 2 in Appendix A) (15, 45).
The NAAQS for sulfur dioxide is 1.3 mg/m3 over a three-hour period, not to be exceeded more than once a year. ADEQ and EPA detected sulfur dioxide levels over eight times this level in residential areas of Douglas in the mid-seventies. EPA also detected 24-hour concentrations about seven times the NAAQS for sulfur dioxide as well.
Past exposures to ambient air contamination were the highest in the early 1970's (and probably before) and have gradually decreased since that time. The declines in mean TSP and sulfur dioxide levels since 1970 are evidence of this trend (see Figures 3 and 4). It is unlikely that people are currently being exposed to any significant levels of the heavy metals (with the exception of lead), or sulfur dioxide because the smelter is no longer operating. People in the area may still be exposed to lead in air because leaded gasoline sold in Mexico and Arizona is an additional source of contamination. Exposure to PM10 also may continue to be a problem because of the growing dust problem in Agua Prieta. Migration of lead to air and ambient dusts is possible, particularly because of the dry, desert climate (i.e., surface soils are loose), and because neighborhood roads are unpaved. Contaminated dusts pose a particular risk because they are easily inhaled and ingested.
Occupational Exposure - Air Pathway
During demolition activities at the Phelps-Dodge Smelter in January 1990, workers involved in asbestos removal were concerned about hazardous occupational exposures to asbestos via inhalation. Consequently, the Arizona Industrial Commission Division of Occupational Safety and Health (AICDOSH) investigated and reported "removal areas appeared to be properly organized and controlled to where the operations were not contaminating...the employees" (3). ATSDR further investigated AICDOSH files and found documentation of air monitoring that revealed asbestos levels as high as 0.9 fibers per cubic centimeter (fibers/cm3). The National Institute of Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL) for asbestos is 0.1 fiber/cm3. If unprotected by equipment and clothing, the workers would have inhaled hazardous levels of asbestos during removal operations. However, during its inspection, AICDOSH observed that all workers wore powered air-purifying respirators (PAPRs) during operations. In addition, the project manager reported that workers had been wearing PAPRs since "the nature of the work and the monitoring results established the need" (3). The petitioner, on the other hand, has reported that PAPRs were not provided during the first four months of the project. Removal operations have been completed and current asbestos exposures are no longer an issue; however, because of the petitioner's report, ATSDR will consider asbestos exposure a past completed exposure pathway of at least four months' duration.
Although no indoor dust monitoring data are available, it is very likely that lead-contaminated soils and dusts have migrated indoors to residential homes. Indoor contamination may result from contaminated soil being tracked in on shoes and clothes, or from contaminated dusts simply blowing in through open windows and doors. Adults and children are therefore potentially exposed to lead-contaminated dusts in their homes by ingestion and inhalation (24). Given the likelihood that household dusts in Douglas are contaminated with lead, the lead exposure pathway could be significant.
Whitewater Draw is a stream that runs on the western border of the former smelter property only during rainy seasons. While it was flowing, Phelps-Dodge discharged wastewater to the draw, and elevated levels of heavy metals were detected. Children who played in the stream in Mexico could have been exposed by ingestion to those heavy metals. While playing, those children would be expected to ingest small amounts of surface water, resulting in short-term or acute exposures. The stream flows directly from the site into Mexico. In all likelihood, neither children nor adults were frequently exposed to the stream since it is usually dry and does not support fish. During the site visit, ATSDR personnel saw no evidence of human activity around the stream bed; however, the stream was dry at the time.
Food Chain, Plants, and Livestock
The suspected origin of lead-contaminated soils in Douglas is the deposit of lead particulate from the former Phelps-Dodge Smelter and auto exhaust from Mexico and Arizona. While the smelter was in operation, lead particulate deposited on local vegetation as well as soils. Residents may have been exposed if garden produce was not rinsed before consumption. Given the level found in residential soils, the garden produce probably did not uptake significant amounts of lead from surface soils (19). During site visits, ATSDR personnel noted that residential gardens in Pirtleville consisted primarily of corn and cabbages.
Cattle ranches are 4 miles north of the former smelter stacks; it is not known whether the area has been contaminated by smelter emissions. It is possible that grasses in the area, contaminated with heavy metals are eaten by cattle and that meat from the cattle is ingested by residents. If the meat from the cattle contains elevated levels of heavy metals, the meat would be another source of heavy metal exposure for residents in the area. Currently, no data support that hypothetical exposure pathway.
Results of groundwater sampling in 1986 showed slight elevations of arsenic and lead levels. The source of that contamination could be naturally occurring arsenic and lead in deep soils. Migration of lead from surface soils to groundwater partially depends on the amount of organic material, the acidity, and the driving force of rainfall. The more organic material for lead to adhere to, the less lead that may migrate to groundwater. Desert soils, such as those in Douglas, have less organic material; however, desert conditions and alkalinity of soil may retard the migration of surface contamination to groundwater. It is unknown if or how much surface contamination has contributed to lead or arsenic concentrations in groundwater.
However, because the groundwater in Douglas flows toward municipal wells in Douglas, any on-site groundwater contamination may have migrated toward these wells. Arsenic was found at the highest level on site in 1989. Heavy metal monitoring of municipal water did show mild elevations of lead and arsenic concentrations in 1984. Elevated arsenic levels were also detected in Agua Prieta; however, lead was not detected. It is unknown if elevations in arsenic levels are directly related to the site, are naturally occurring, or are related to some other source.
It is also possible that on-site groundwater contamination may have intercepted private wells downgradient from the site. No monitoring data from private wells were available at the time of this report.
The slag pile on site contains elevated levels of copper. Access to the site and the slag pile is restricted by fences; however, that restriction is inadequate to prevent trespassing. Children and adults could gain access to the slag pile with little effort. If children played on or near the slag pile, they could ingest slag through normal hand-to-mouth activity. A level of 806 mg/kg copper (nearly three times background levels found in that area) was detected in the slag. However, ADHS reports "a child would have to ingest over 6.5 grams of slag per day to approach a copper intake level that would result in any adverse health effect (gastrointestinal upset)" (4). Slag itself is hard and rocky and typically in one-inch chunks; therefore, incidental ingestion and subsequent adverse health affects related to heavy metal contamination are highly unlikely (12, 45).
The potential for heavy metals found in the slag to leach to surface water has not been thoroughly investigated. ADEQ reports that there is potential for copper and lead to leach to surface or groundwater under the right conditions, although the leach tests were not extraordinarily high (12, 45, 47).
The Public Health Implications section of this public health assessment evaluates the toxicological effects of exposure to specific contaminants, state and local health databases, and specific community health concerns.
The most likely pathways of exposure to contaminants of concern for people who live near the Phelps-Dodge smelter are 1) breathing air (especially in the past when the smelter was operating); and 2) ingesting dust and soils. Another potential, but less likely, pathway of exposure is contact with contaminants in the surface water of Whitewater Draw (when the stream is flowing).
Evaluating potential toxic effects includes estimating the amount of contaminants that a person contacts daily, which depends on the frequency and duration of exposure (e.g., short-term or continuous). The public health risk is greater for people exposed for some critical length of time to contaminants at levels greater than established health guidelines.
Health guidelines are developed for contaminants commonly found at hazardous waste sites. Examples of health guidelines are the ATSDR minimal risk level (MRL) and the EPA reference dose (RfD). The MRL and RfDs are estimates of daily human exposure to a contaminant below which adverse health effects are not expected. MRLs usually are calculated for ingestion and inhalation, and for acute (less than 14 days), intermediate (15 to 365 days), or chronic (more than 365 days) lengths of exposure.
ATSDR discusses many health guidelines in its Toxicological Profiles, which also provide chemical-specific information on health effects, environmental transport, and human exposure. For this public health assessment, those profiles were consulted for toxicological evaluations of arsenic (26), asbestos (35), benzene (36), cadmium (37), copper (38), and lead (24).
Heightened concern about the health effects of lead has resulted in increased public health efforts to minimize environmental exposures. The concerns stem from evidence that children and developing fetuses are especially sensitive. Lead is particularly toxic to children because it affects physiologic systems important to their development and maturation. Blood lead levels as low as 10 µg lead per deciliter (µg/dL) of blood have been associated with impaired learning in children.
Exposure to lead paint or paint chips remains the most common cause of severe lead poisoning in children. Other potentially important sources of lead exposure include soil and dust, as well as "take home" exposures from parental occupations and hobbies, water, and food. In Hispanic communities, folk remedies such as "azarcon" and lead glazed ceramic cookware are also sources of lead exposure for children (20, 21, 22). The discussion below focuses on lead exposure through contact with contaminated soil, groundwater, and air. While not the only source of lead exposure for this community, these environmental media may make a significant contribution to elevated lead levels in children, thus warranting discussion here in addressing the public health implications of the Phelps-Dodge site.
In addition to the affects of lead on children, there is qualitative evidence to support the conclusion that, at high exposure levels, lead can significantly adversely affect reproduction. Increasingly, miscarriages have been reported in women living close to a lead smelter (23).
Soil. Whether lead is toxic or not depends upon the amount or dose a person receives, the duration of exposure (acute, intermediate or chronic), and variation in people's responses to exposure. Exposure to high levels of lead in soil (100-1,000 milligrams of lead per kilogram soil [mg/kg]) can result in elevated concentrations of lead in blood (23). Chronic ingestion of lead-contaminated soils by children through normal hand-to-mouth activity can lead to impaired learning (especially in children with pica behavior who ingest excessive amounts of non-food items).
The average levels of lead found in soil off the Phelps-Dodge smelter site (in the Pirtleville community and Douglas) ranged from 100 to 341 mg/kg. Residential soils closest to the smelter (i.e., in the Pirtleville area) typically were most contaminated with lead. Those lead levels suggest the need for blood lead testing of children. Although the Phelps-Dodge smelter is no longer discharging lead, soil lead levels will remain elevated for years, and the dry climate contributes to dusty conditions, thereby increasing exposures.
Groundwater and Surface water. Migration of lead from surface soil to groundwater is unlikely given the strong adsorption of lead to soil. The maximum level of lead found in off-site groundwater was 20 µg/L. This exceeded the EPA's Maximum Containment Level of 15 µg/L. Current public health efforts are aimed at reducing lead levels in water to zero, which suggests the need at the site to continue to monitor groundwater used for drinking.
The surface water lead levels (maximum of 360 µg/L) are not of public health concern because ingestion is considered incidental (i.e., the contaminated water is not a drinking water source, and people would ingest only very small amounts as a result of other activities).
Surface water. The Whitewater Draw is not used for drinking water, and exposures to it are expected to be short term (not more than 14 days). A reasonable maximum exposure for school-age children, who might play occasionally in the Whitewater Draw, is assumed to be a few ounces (i.e., 10-100 ml) of water ingested per day three days a week. ATSDR estimated conservative surface water ingestion doses using the highest concentration of arsenic found in Whitewater Draw. The estimated arsenic exposures near the site are far below levels (during short-term exposures) that cause adverse effects.
Air. An increased risk of lung cancer has been reported in populations of arsenic-exposed smelter workers. Douglas residents, who are exposed to arsenic in off-site ambient air, have a considerably lower risk of cancer. The highest arsenic concentration measured in ambient air, 0.1 µg/m3 (Table 6), is a measurement of arsenic levels in ambient air between 1970 and 1987. Assuming that people were exposed to that amount of arsenic continuously (every day) for 15 years, one case of cancer, at most would be expected for every 10,000 Douglas residents. If a typical (median) arsenic concentration is assumed to be representative of exposure, we can conclude that cancer is unlikely to result from breathing arsenic in the air at this site.
Soil. Currently, no data on levels of arsenic in off-site soil are available for toxicological evaluation.
Asbestos is considered a human carcinogen because workers with occupational exposure have been found to have an increased risk of two types of cancer: cancer of the lung tissue and mesothelioma, a cancer of the thin membrane surrounding the lung. The relative risk of lung cancer is much higher for asbestos workers who smoke than for those who do not.
Occupational exposure to asbestos is also associated with asbestosis, a lung injury that causes shortness of breath.
Air. Airborne asbestos was reported in 1990 during demolition of the Phelps-Dodge smelter, which included removal of asbestos. The asbestos levels detected were as high as 0.9 fiber per cubic centimeter (fiber/cm3) of air. The Occupational Safety and Health Administration (OSHA) permissible exposure level (PEL) for asbestos over an eight-hour period is 0.2 fiber/cm3; the National Institute of Occupational Health and Safety recommends 0.1 fiber/cm3. Assuming that asbestos removal workers were exposed continually to the maximum level of asbestos measured (i.e., they did not have adequate protective breathing apparatus during the first few months of asbestos removal), they may have an increased lung cancer risk.
Air. Benzene is released into the atmosphere from both natural and artificial processes. The most significant outdoor environmental source appears to be the burning of gasoline in automobiles. Levels of benzene measured in the atmosphere range from about 0.001 milligrams per cubic meter (mg/m3) in rural areas to maximum levels of more than 0.1 mg/m3 in some urban areas.
In the past, benzene was one of the most common industrial solvents; it is now rarely used in the workplace. The main reason for the reduction in use has been concern about whether it causes cancer of the white blood cells (primarily acute myelogenous leukemia) and aplastic anemia in exposed workers. In addition, exposure to the relatively high levels of benzene found in some industrial settings can result in workers having reduced blood platelets, red blood cells, and white blood cells. Depression of immune function also has been documented (36).
The highest benzene level detected (0.01 mg/m3) in ambient air samples taken near the Phelps-Dodge smelter is well within the range of values typical for ambient air in the United States, but about 10 times higher than values commonly seen in rural ambient air. Nevertheless, no adverse health effects (cancer or noncancer) would be expected in people exposed to benzene at that level.
Groundwater and surface water. Estimated ingestion doses of children exposed to cadmium in the site area, which were calculated using the highest concentrations of cadmium observed in groundwater, are slightly lower than health guidelines used by ATSDR (Table 4). Cadmium concentrations in the surface water (Table 5) are about 10 times higher than those found in groundwater samples. The potential for contact with cadmium in surface water is not great (see previous discussion of exposure to arsenic in surface water). Currently, there is no significant community exposure to cadmium in groundwater or surface water, but there appears to be a potential threat of groundwater contamination and a need to monitor groundwater sources used for drinking.
Air. Cadmium was detected at 0.000078 mg/m3 in air samples (Table 6). At that level, the estimated amount of cadmium people might inhale does not exceed the ATSDR health guideline (i.e., the chronic MRL). Therefore, no adverse noncancer health effects (e.g., kidney disease) are expected. In terms of cancer risk, some studies suggest a risk of cancer (respiratory, prostate, and genitourinary) for workers in various metals industries who are exposed to high levels of cadmium. It is very unlikely that exposure to the levels of cadmium in ambient air in Douglas would cause cancer in residents.
The National Ambient Air Quality Standards (NAAQS) are guidelines for air pollutants that can endanger the public health or welfare. The NAAQS for particulate matter with a diameter less than 10 microns (PM10) is 0.15 mg/m3 for a 24-hour period, not to be exceeded more than once a year. The presence of PM10 in air is significant to public health because particles of that size are small enough to penetrate deep into the lung. PM10 levels as high as 0.221 mg/m3 were reported in residential areas while the Phelps-Dodge smelter was operating (1970-1987) (3), and may have adversely affected health and the quality of life for residents of Douglas. In 1992, PM10 levels averaged 0.04 mg/m3. The maximum level detected was 0.137 mg/m3, above the NAAQS of 0.05 mg/m3. This suggest that PM10 continues to be a health concern for Douglas residents, even though the smelter is no longer operating.
Residents were exposed to sulfur dioxide in the past during operation of the smelter; current exposure is not considered of public health concern. The NAAQS for sulfur dioxide is 1.3 mg/m3 for a 3-hour period, not to be exceeded more than once a year. Sulfur dioxide levels were detected at levels as high as 9 mg/m3 in residential areas.
Some evidence supports an association between particulate pollution and respiratory problems in susceptible people, including children and people with respiratory ailments (asthma) (39).
Trace Elements and Metals
Surface water. Several trace elements (i.e., barium, chromium, manganese, selenium, and zinc) typically found in raw water supplies and soil in the United States were found in Whitewater Draw surface water. At low levels, chromium, copper, manganese, selenium, and zinc are essential trace elements in the diet and are vital to several enzyme systems or processes in the human body. Barium, on the other hand, has no known human nutritional benefit.
ATSDR calculated reasonable estimated exposure doses (as was done for arsenic in surface water) using the highest levels of barium, chromium, manganese, selenium, and zinc found in surface water (Table 5); people were not exposed to the elements and metals at levels that exceed ATSDR health guidelines. Therefore, exposures to the elements and metals were not of public health concern.
Air. Manganese was detected in off-site air (0.0005 mg/m3), but not at a level of public health concern. Manganese levels in air did not exceed the ATSDR chronic inhalation MRL.
Evaluation of health outcome data may give a picture of the general health of a community. Elevated rates of a particular disease should not automatically be associated with hazardous substances in the environment. On the other hand, even if there is no apparent evidence of elevated rates of disease in a community, a contaminant may still be responsible for illness or disease.
ATSDR uses routinely gathered data when conducting public health assessments. Such health outcome data typically are reported for people in population groups such as cities and counties. The people likely to have been affected by the contaminants associated with a particular site, however, are usually part of smaller groups of people (e.g., subdivisions, streets). Because of the limitations of current analytical methods, any evidence of contaminant-associated illness or disease in the smaller group may be hidden within the rate of disease of the larger groups.
In addition, when exposed or potentially exposed populations are small, the number of people who may develop a particular illness or disease is also small. Small changes in the number of affected people from year to year can cause a large change in the rate; such a rate is considered "unstable." In epidemiology, it is difficult to determine if a change in an unstable rate is due to normal fluctuation in numbers of diseased persons in a population, or some change in that population's environment.
Center for Disease Control Study (16)
In 1975, the Center for Disease Control researched absorption of heavy metals by children living in smelter towns; Douglas was one of the towns included in the study (the study was published in 1977). Results were compared with data on 258 children of the same age in three communities without smelters (see (Table 8), Appendix B, for a summary of the average levels detected in Douglas children).
The biomonitoring techniques used in the study were all appropriate measures of exposure; some have limitations, however, which are discussed in the following paragraphs. Measurement of lead in blood is used to help determine if exposure to lead has occurred within the past 4 to 8 weeks. Measurement of arsenic in urine is the most reliable means of detecting recent (within the past several days) arsenic exposures. Measurement of arsenic from hair samples can detect exposure within the past 6 to 12 months to high levels of arsenic (41). Measurements of cadmium, lead, and arsenic in hair samples may not be entirely reliable, however, because those measurements may reflect not only the amount of metals uptake into the hair shaft from the system, but also the amount of metal deposited on the hair. Only the metals uptake into the hair shaft is a useful measure of exposure (26).
Evaluation of the metals data indicated that Douglas children had increased exposure to arsenic, lead, and cadmium. Their lead, arsenic, and cadmium levels were elevated compared with children from other Arizona communities without smelters (41).
In addition, the biomonitoring data indicated that the children's exposures may have been of public health significance. Average blood lead levels were more than double the current CDC-recommended level of 10 µg/dL. Fifteen children had blood lead levels greater than 29.4 µg/dL. Chronic elevated levels of lead in the blood have been associated with impaired learning ability in children (see discussion in the previous Toxicological Evaluation section). The data indicate that the children tested in 1975 had blood lead levels which have been associated with nervous system effects, including impaired learning, decreased stature or growth, decreased hearing acuity, and decreased ability to maintain a steady posture (22).
1985 Arizona Department of Health Services Followup to the 1975 CDC study (4).
As was the case in 1975, the results of the 1985 monitoring of lead in the blood of Douglas children indicated that they had been exposed (see Table 9, Appendix B). Blood samples from 114 children were tested; the average blood lead levels exceeded the current CDC-recommended level of 10 µg/dL, but were lower than the blood lead levels measured in 1977. The children were categorized according to exposure parameters (e.g., the presence or absence of pica behavior or distance of residence from the Phelps-Dodge Smelter). Overall, the children's blood lead levels ranged from 3 to 24.8 µg/dL. Children without pica behavior and those who lived closest to the Phelps-Dodge stacks had the highest average blood lead levels. Blood lead levels correlated with soil lead levels; on average, soil lead levels were greater in soils closest to the Phelps-Dodge smelter. Surprisingly, it was found that, on average, children with pica behavior had lower blood lead levels. Researchers believed the finding may have been caused because of confusion about the definition of pica among the mothers interviewed.
Some quality control information was available for this monitoring. For the blood lead measurements, ADHS split the samples and sent them to their lab and to the CDC. The results indicated that the ADHS lab detected blood levels that were generally about 33% higher than the levels detected by CDC. If the average blood lead levels found by ADHS are reduced by 33%, the results still indicate averages of about 10 µg/dL.
ADHS also measured for arsenic in 134 urine samples from the children. Six children had urine arsenic levels greater than 50 µg/dL. Two children had urine arsenic levels greater than 100 µg/dL (130 µg/dL). The elevated arsenic levels could be associated with diet as well as with environmental exposure. Generally, urine arsenic levels in Douglas children were in the range of what would be expected in the general population.
Blood lead monitoring information since 1992 (48)
The Cochise County Health Department diagnosed a child with a blood lead level of 30 µg/dL in January 1992. The child had a history of pica behavior and lived in an area that had elevated soil lead levels in 1985 (averaging 250-350 mg/kg lead in soil). The child was referred to the University of Arizona for treatment. The local sanitarian conducted an exposure assessment to determine possible sources of lead exposure for the child. The sanitarian identified elevated levels of lead in soil and a piece of furniture in the yard that had chipping lead paint. The paint was tested and found to contain high levels of lead (>10,000 parts per million). Exposure to the leaded paint in the furniture was probably the main source of the child's elevated blood lead level.
In 1993, 144 Douglas/Pirtleville children were tested for lead under the AHCCCS program. Three elevated blood lead levels were detected. Two were less than 20 µg/dL, so the parents received counseling. The other was a previously identified child for whom lead-based paint had been already identified as a likely source of exposure.
In 1994, seven cases of elevated blood lead levels were identified (the total number of children tested is unknown at this time). Three cases were less than 20 µg/dL. The most likely sources of exposure in the investigated cases were identified as lead-based paint, paint-contaminated soil, and the folk medicine, Azarcon. All four cases live at least 2.5 miles from the Phelps-Dodge site.
1979 Smelter Environmental Research Association (SERA) Study (17)
Lung cancer incidence from 1970 to 1977, within a 20-kilometer radius of nonferrous smelters in six western states, was evaluated using the case-control approach. A case-control study compares two populations. In this example, the lung cancer rates in people who live near smelters were compared with lung cancer rates in people who do not live near smelters. Also, rates of other cancers (not associated with exposure to smelters) were compared in the two populations, to control for populations who may have a general increase in all types of cancer, not just lung cancer. Douglas, AZ, was one area studied in 1979 using this case-control approach. Addresses of lung cancer patients at time of diagnosis of lung cancer were obtained and plotted on U.S. Geological Survey maps. Distance and location of the addresses from smelters were measured.
Because no state cancer registry existed at the time of the study, information about cancer incidence in Douglas was gathered from death certificates. A sample of 120 cancer deaths was obtained (56 cases, 62 controls). Information on occupation and sex were available and controlled for (using the Mantel-Haenszel chi square test for significance). The study found that developing lung cancer was not related to location of residence; the incidence of cancer was no higher in people who lived closer to the smelters. However, the very small sample size of each smelter and nonsmelter area means that there would have to be a large difference in lung cancer rate cases and controls before such a difference would be observed. Standard mortality ratios (the number of diseases observed in the exposed population divided by the number expected for that population) were also calculated for lung cancer mortality in both men and women (see Table 9, Appendix B). The ratios indicated that there was no statistically significant increase in lung cancer deaths over the number expected for either men or women.
Several limitations to this study should be noted. First, the authors did not discuss the control population. The authors also did not separate the lung cancer rates by age group (a confounding factor) before calculating the standard mortality ratio. A confounder is a factor that could also be related to the health outcome of interest (i.e., lung cancer). By not controlling for confounders, researchers may bias the results of the study. Important confounding factors for lung cancer, such as smoking, were not controlled.
The small sample size of the study population in Douglas also is a limitation of the study. Previously in this public health assessment, it was estimated that chronic ambient air exposures to contaminants at levels detected off site could result in a low increased cancer risk. However, the very small sample size of lung cancer deaths in Douglas means that a large difference between cases and controls must be shown (i.e., more cancer in cases than controls) before it could be concluded that smelter emissions were associated with lung cancer. The sample size was not large enough to detect a small increase in the rate of lung cancer deaths (41).
In summary, because of numerous methodologic problems, the results of the SERA study have limited application in evaluating lung cancer in Douglas. ADHS is conducting another study of populations in smelter areas, and Douglas is included. This study will further investigate health outcome data for populations exposed to smelter emissions.
School health officials evaluated five cases of autoimmune illnesses among teachers at the Faras Elementary School. Investigation indicated that the causes of the five illnesses were not related to each other or to environmental exposures that may have occurred while the teachers worked at the elementary school (14). For instance, cases were diagnosed before living in Douglas, and other cases had genetic etiologies (14).
Studies indicate that learning disabilities are associated with lead exposure during development of the fetus. Other factors associated with learning disabilities include genetics, malnutrition, or injury. Percentages of learning disabilities in children attending elementary schools in Douglas are similar to each other. Faras Elementary School had the highest percentage of learning-disabled students (15%) (34).
Although the percentage of learning-disabled students at Faras Elementary is greater than at other Douglas schools, the differences between the schools are so slight that the cause of the differences cannot be determined or correlated with environmental exposure.
Birth Defects Registries
The Arizona Birth Defects Monitoring Program provided information about the rate of birth defects for Cochise County for 1987. The birth defects rate is defined as the rate of birth defects per 1,000 live and still births. The birth defects rate for Cochise County for 1987 was below the state rate. The ADHS Arizona Birth Defects Monitoring Program recently released a report that addresses the occurrence of neural tube defects (anencephaly and spina bifida) in southern Arizona. Results indicated that rates of neural tube defects were not elevated in Cochise County. However, Cochise County rates have limited value for characterizing birth defects in Douglas because Cochise County has a much larger population. Because of the difference in population size, a high or low rate of birth defects in Douglas might not be reflected in the county rate.
Summary of Health Outcome Data Evaluation Section
Blood lead levels were sufficiently elevated in 1977, 1985 and since 1992 for those children to be at risk for adverse neurological effects, such as decreased ability to learn in school. Soil lead contamination may be one source of lead exposure for these children; however, other sources should be considered as well. Cancer rates in 1979 showed no significant increase in Douglas over controls. Because of numerous methodological problems, the results of the SERA study have limited application in evaluating lung cancer rates in Douglas. Lung cancer rates are currently being studied by ADHS. Birth defect and learning disability rates did not appear to be significantly elevated, and the cluster of autoimmune diseases at the Faras Elementary School were not related to exposure to site contaminants.
ATSDR has addressed each of the community concerns about health.
- The petitioner expressed concern about exposure to asbestos during asbestos removal operations at the smelter.
On-site monitoring during asbestos removal operations detected ambient asbestos levels as high as 0.9 fiber per cubic centimeter (fiber/cm3). Currently, the National Institute of Occupational Safety and Health's recommended action level for asbestos is 0.1 fiber/cm3. Although reports by OSHA stated that removal operations were conducted in compliance with safety regulations, asbestos removal employees reported that respirators were not provided at the onset of the operation. Assuming that workers were exposed (8 hours a day for 3 months to the maximum level of asbestos measured) without adequate breathing apparatus, the exposed workers may have an increased lung cancer risk, particularly if they also smoked cigarettes.
- Members of the Border Ecology Project expressed concern about the public health impact of past emissions from the smelter.
While the smelter was in operation, lead emissions could have contributed to elevating blood lead levels in children. Severe cases of lead poisoning in children usually result from ingesting lead paint or some other direct ingestion of food or water highly contaminated with lead. However, new research indicates that even low levels of lead in children's blood (10 µg/dL) may have subtle adverse health effects such as impaired learning ability. Exposure to lead in air and soil may have contributed to the elevated blood lead levels found in Douglas children in 1985.
People also were exposed to sulfur dioxide during past smelter operations. The NAAQS for sulfur dioxide is 1.3 mg/m3 for a 3-hour period, not to be exceeded more than once a year. Sulfur dioxide levels were detected at levels as high as 9 mg/m3 in residential areas, but it is not known how often and to what extent sulfur dioxide levels exceeded NAAQ standards. Exposure to sulfur dioxide at those levels could have exacerbated respiratory problems in susceptible people, such as children or people with respiratory ailments (e.g., asthma) (39). ADHS is conducting a study of populations surrounding smelters, and Douglas is included. Results will help evaluate the public health impact of past emissions exposures.
- Members of the Border Ecology Project expressed concern about potential health effects of hazardous substances they believe were buried on site.
In 1990, EPA investigated claims of buried cyanide on site. Smelter workers identified areas where wastes were suspected of being buried, and EPA then dug beneath the areas. The investigation did not find hazardous substances buried on site. ATSDR will assist in contacting appropriate staff at EPA to investigate any other reports of buried hazardous wastes on site.
- Members of the Border Ecology Project expressed concerns about the potential health effects of heavy metals in on-site slag deposits leaching to the nearby Whitewater Draw.
ADHS reports that heavy metals identified in the on-site slag pile are not prone to leaching. Analysis of surface water samples from Whitewater Draw revealed only trace amounts of heavy metals. The levels found are unacceptable for drinking water, but are not considered a public health threat for human contact are during normal recreation.
- Members of the Border Ecology Project are concerned that contaminants in air, surface water, and groundwater have migrated from the smelter site to residential areas in Douglas and Mexico.
Pathways analyses and off-site monitoring data reveal that contaminated air has migrated to residential areas in Douglas (see Community Health Concern Evaluation #2). Given the proximity of the former smelter to Agua Prieta, past migration of smelter emissions to residential areas in Mexico was likely.
From available data, ingestion of groundwater does not currently pose a risk to the health of residents of Douglas. Migration of lead-contaminated surface soil to groundwater is unlikely because lead strongly adsorbs to soil. Migration of other heavy metals from on-site soil to groundwater may be possible. The actual direction of groundwater flow is unknown at this time. Changes due to pumping may have reversed the direction of groundwater direction. If on-site groundwater has been contaminated, it may migrate in a southerly direction into Mexico. ATSDR staff noted that elevated levels of arsenic and cadmium were found in municipal groundwater wells in Mexico. ATSDR is cooperating with Mexican authorities to further investigate possible environmental health threats, including contaminated groundwater, in Agua Prieta.
- Members of the Border Ecology Project are concerned that the elevated blood lead levels in children living in Douglas are the result of chronic exposure to lead-contaminated soil.
The Centers for Disease Control recently reduced the blood lead standard to 10 g/dL. Judged against this new standard, Douglas children on the average had mildly elevated blood lead levels in 1985. As recently as January 1992, a blood lead level of 30 g/dL was detected in a 3- year-old child with pica.
Currently, contaminated soil and dust may be a source of lead exposure in Douglas. When the smelter was operating, lead particulates in ambient air may have been an additional source of lead exposure. Other sources of lead exposure for Douglas children include lead paint and paint chips, leaded gasoline in Mexico, and possibly lead-glazed ceramic cookware and folk remedies such as Azarcon.
- Members of the Border Ecology Project are concerned about the effects on soil in Douglas and Agua Prieta of other potential airborne industrial discharges.
According to available environmental monitoring data, the Phelps-Dodge Smelter was the primary source of airborne industrial contaminants in the area. A search of EPA's Toxic Chemical Release Inventory database did not indicate any other sources of heavy metal contamination in the city of Douglas, or in the zip code region. If specific information on other industrial sources of environmental contamination becomes available in the future, ATSDR will evaluate that information. Although it is gradually being phased out, leaded gasoline is available and is used in Mexico. Auto emissions from cars that use leaded gasoline also may contribute to elevated levels of lead in soil in Douglas. In the past, leaded gasoline was a significant source of lead exposure for children in the United States.
- ADHS expressed concern about the potential for people to inhale contaminated dust in Douglas; about elevated blood lead levels in children; and about the lack of a routine blood lead monitoring program.
According to the exposure pathways analyses in this public health assessment, inhalation and ingestion of lead- contaminated dusts in Douglas may be a significant source of lead exposure for children in the area, although dusts have not been monitored to confirm the inhalation pathway.
Chronic elevated levels of lead in blood have been associated with impaired learning ability in children (see the Toxicological Evaluation section of this public health assessment). Blood lead monitoring results from Douglas indicate that some children tested in 1975 and 1985 had blood lead levels that have been associated with nervous system effects, including impaired learning, decreased stature or growth, decreased hearing acuity, and decreased ability to maintain a steady posture (22).
- Community members are concerned about apparent high rates of the following illnesses:
birth defects - Arizona maintains a birth defects registry, which indicates that the overall birth defects rate for Cochise County is not greater than the state rate (see the Health Outcome Data Evaluation section of this public health assessment).
collagen diseases - There is no evidence that supports or refutes an association between exposure to site-related contaminants and collagen diseases in the literature.
cancers of the breast, bone, and cervix - There is no evidence that supports or refutes an association between exposure to site-related contaminants and cancers of the breast, bone, or cervix.
diabetes - There is no evidence that supports or refutes an association between exposure to site-related contaminants and diabetes.
learning disabilities in children - Rates of learning disabilities in Douglas children are recorded in Appendix B. Because learning disabilities may have several or even unknown causes, relating the disability to environmental factors, such as lead exposure, is very difficult to do. Research indicates that elevated lead levels in children may affect their IQ. There are no studies that relate learning disability rates in schools to lead contamination. Therefore, it is possible that environmental lead exposures in Douglas may have affected the children's behavior and IQ, but we cannot conclude that the rate of learning disabilities in Douglas schools has also been affected. Currently, Douglas schools rate of learning disability is similar to state rates.
first-trimester miscarriages - Evidence supports the conclusion that, at high exposure levels, lead has significant adverse effects on reproduction. For example, an increased frequency of miscarriage has been reported in women living closest to lead smelters. Lead exposures at copper smelters, such as the Phelps-Dodge smelter, would be significantly lower; therefore, the risk of reproductive effects would be much less.
asthma - Although none of the contaminants detected in off-site air cause asthma, many may aggravate the existing condition. Sulfur dioxide and dust (inhalable particulate) are lung irritants that can cause transient asthmatic symptoms or chest discomfort following acute exposures. The concentrations of those contaminants in ambient air (measured during the operation of the smelter, 1970-1987) were great enough to cause those adverse effects in sensitive subpopulations.
allergies - Allergies would not be caused by contaminants found at this site. However, residents who are allergic to dust, or who are hypersensitive to contaminants, such as sulfur dioxide, found off site, may have experienced a worsening of symptoms while the smelter was operating. Residents with dust allergies may have noticed an increase in symptoms during the past few years because of the increase in ambient dust.
ear infections in children - There is no evidence that supports or refutes an association between exposure to site-related contaminants and ear infections in children.
children needing glasses - There is no evidence that supports or refutes an association between exposure to site-related contaminants and worsening eyesight. Some contaminants released to air in the past may have caused eye irritations (e.g., sulfur dioxide).
- Community concerns about the following environmental conditions and their effect on public health also were identified:
lack of ground surface vegetation and the difficulty of maintaining grass in yards - Decreased ground cover and difficulty in growing grass is typical of the desert environment. However, poor ground cover can result in increased exposure to lead-contaminated soils, (e.g., because there is no grass barrier between the children and the soil during outdoor activity). Lack of ground cover also means that soils are more prone to wind erosion, and levels of ambient dusts are likely to be greater, further increasing exposures. Because it may result in increasing exposures of children to lead-contaminated soil, lack of ground surface cover is a valid concern. The soil lead pathway is discussed in greater detail in the Pathways Analyses section of this public health assessment.
dusts in the air and in homes - It is likely that lead-contaminated soil has migrated indoors and resulted in formation of lead-contaminated household dusts. Exposure to those dusts also may be a significant exposure pathway, although no monitoring data support it. Dusts in ambient air have been a growing problem in Douglas during the past few years. Ambient dusts may represent significant exposure because they may be inhaled as well as ingested. It is not currently known if ambient dusts are contaminated with heavy metals.