VII. Conclusions

This PHA considers use of water resources as a sole source of drinking water over a lifetime. However, the evaluations and therefore the conclusions discussed in this section do not yet include any contribution from other sources of contamination that the residents of Vieques may encounter. As other sources are investigated, any additional exposures will be evaluated in conjunction with these findings to determine cumulative effects.

ATSDR has categorized this site as having no apparent public health hazard. In evaluating exposures to contaminants found in Well 3-7, ATSDR concluded this well posed a public health hazard; however, PRDOH issued an advisory for this well and notified the residents not to use it to supply drinking water. Because no data are currently available, ATSDR concludes that rainfall collection systems pose an indeterminate public health hazard. (Definitions of public health categories are included in the glossary in Appendix A.) Conclusions regarding the drinking water sources evaluated by ATSDR are as follows:

• The majority of the residents receive their drinking water from the mainland of Puerto Rico. Three different agencies tested the drinking water within the public water supply system. After an evaluation of the results of these tests, ATSDR concludes that the public drinking water supply is not being impacted by the bombing range activities and is safe to drink.
• Groundwater cannot travel from the LIA across the island to residential areas of the island. Therefore, groundwater from the LIA is not impacting groundwater in the residential area of Vieques.
• Some residents may supplement their drinking water supply by using water from groundwater wells. EPA and PRDOH sampled various groundwater wells and ATSDR evaluated the results. The water from the three Sun Bay wells, the four B wells, and Well 2-3 is safe to drink whenever the public water supply is interrupted. However, residents who are on a sodium-restricted diet should be cautious when drinking water from these wells.
• One private well (Well 3-7) showed high levels of nitrates plus nitrites. The water from Well 3-7 is not safe to drink, especially for children and pregnant women. In October 1999, PRDOH issued an advisory and personally informed residents that water from this well is not safe for consumption. ATSDR agrees that residents, especially children and pregnant women, should not drink the water from Well 3-7. Because of the hydrogeology of the island and analysis of other groundwater wells in the area, ATSDR does not believe that the high level of nitrates plus nitrites in groundwater is a consequence of the bombing range activities; rather, it is probably a result of agricultural activities or septic systems in the area.
• The location, use, and extent of contamination in rainfall collection systems are not available. Therefore, the potential impact from drinking water from rainfall collection systems cannot be evaluated at this time. ATSDR's evaluation of the air pathway will provide additional insight into this potential exposure route.
• Very low levels of RDX, tetryl, ammonia, and nitrate plus nitrite may have been present in drinking water samples taken by the Navy in 1978. However, ATSDR has doubts about the validity of the data because of the small number and description of the samples. The authors of the report noted that "a completely positive identification was not possible due to the extremely low concentrations found" (Hoffsommer and Glover 1978). The levels of nitrate plus nitrite are consistent with groundwater on the island and are not conclusive evidence of explosive contamination. In addition, more recent analyses of drinking water samples did not detect any explosive related contamination. The concentrations of explosive compounds reported in drinking water in the past were well below levels considered harmful to human health and past exposure to these compounds does not pose a public health hazard.
• There is no evidence that residents of Vieques have been exposed to additional levels of radiation as a result of the February 1999 use of depleted uranium (DU) rounds in the LIA. Based on samples taken from across Vieques, the NRC concluded that there was no spread of DU to areas outside the LIA. The levels of radiation detected in soil, vegetation, and water by the NRC investigators are consistent with normal radiation background levels and do not represent a public health hazard.