HUNDREDS of thousands of Costa Ricans in theCentral Valley could be drinking water heavily lacedwith cancer and mutation-causing pollutants, likelyfrom septic tanks and coffee plantations.Three long-term studies of underground water inthe Virilla River basin in the western Central Valleyrevealed nitrate and other contaminant levels indrinking water approach or exceed maximum limitsrecommended by health authorities.Investigators of the Universidad Nacional (UNA)in Heredia, north of San José, periodically monitored11 wells and nine springs in the basin from 1990-2002.The aquifers underlying the territory serve morethan a million residents, and 20% of the water sourcesstudied contained dangerous levels of nitrates on atleast one occasion. And the levels are rising, theinvestigators discovered.“IF measures are not taken, in a few years thiswater will not be able to be used for human consumption,”said Jenny Reynolds, head of UNA’sEnvironmental Hydrology Center.UNA investigators this week released the resultsof the studies, funded in part by the International Atomic Energy Agency and the CostaRica-United States of America Foundationfor Cooperation (CR-USA).The Virilla River basin is sprawled overan area of nearly 1,000 Km2, which is 2% ofCosta Rica’s total land, but home to 43% ofthe country’s population. UNA investigatorspoint fingers at this concentration of humanity,its constellations of industries, plantationsand rivers of untreated sewage, forcontaminating aquifers.Nitrates, found in sewage and fertilizers,seep into the region’s volcanic aquifers fromseptic tanks and coffee plantations, whileharsh chemicals in industrial waste andspills, called volatile organic compounds,leak into water sources and wreak unpredictablehavoc on the drinkers’ health.“UNFORTUNATELY, it (the pollutionof underground water) is a slowprocess, which means when the contaminantsare detected, it is hard to reverse theprocess,” Reynolds said.Volatile organic compounds are carcinogenicand mutagenic in low levels,Reynolds said. The degree to which healthis affected is uncertain, however, becausetests on humans are not easily conducted.Paints, glues, solvents such as perchloroethylene– the main solvent used indry cleaning – paint and lacquer thinners,insect repellents, air fresheners, hobbysupplies, wood preservatives, aerosols,degreasers and automotive products areamong those that release volatile compounds.Their effects on health vary from hightoxicity to none, depending on the compoundand the level and length of exposure,according to the U.S. NationalLibrary of Medicine.LONG-TERM exposure can causeliver, kidney and central nervous systemdamage. Short-term exposure can cause a listof symptoms from headaches and skin reactions,to nausea and forgetfulness.The compounds are easily washed intogroundwater sources, UNA scientists report,such that even a small spill can pollute “millionsof liters of subterranean water.”Three times between 1999-2004,investigators tested 32 sites in the VirillaRiver basin for the compounds. The waterwas drawn from wells and springs fed bythe upper and lower Colima aquifers andthe Barva aquifer, one of the most important– and closest to the surface – drinkingwater sources in the region. Of those, ninewere polluted with volatile compounds.“In general, the concentrations do notsurpass maximum levels permitted, but thefact that they are present indicates thatthere is an active process of contamination,”the investigators report.REYNOLDS highlighted one of theregion’s cantons, Belén, as the most highlypolluted of the area, hypothesizing thatits recent population explosion and correspondingindustrial development could bethe culprit.More than 20,000 people are squeezedonto Belén’s 12 Km2, which they sharewith 70 industrial establishments, theinvestigators report.“I can’t confirm the causes (of waterpollution in Belén), but we can assume it’sindustry,” Reynolds said.An important water source in the riverbasin is the spring Ojo de Agua, located inthe swimming and recreational area of thesame name. The investigators found it has“relatively high concentrations of volatilecompounds.”They mention the spring and the discoveryof contaminants in two wells drawnfrom the Colima aquifers, which are muchdeeper than Barva, as “worrisome” becauseit appears the soil and rock layers above thewater are not sufficient protection.“The management of water in theCentral Valley is not sustainable – that meanswe can’t guarantee clean water for our childrenor grandchildren,” Reynolds said.THE Barva aquifer has been underUNA’s microscope since 2001. The studyaimed to enlighten city planners to thedimensions, characteristics and vulnerabilitiesof this shallow-set aquifer thatsupplies water to 500,000 people in theCentral Valley.It is beneath some of the country’s heaviestpopulation growth regions, where theconcrete and pavement block some of theaquifer’s recharge zones, making rain andgroundwater run off rather than seep in.The investigators call for a subterraneanwater-management plan based on the resultsof their studies. They recommend thatsprings and wells be zoned off and regulatedto protect their purity, septic tanks be phasedout of use, replaced with sewage pipes andwaste-water treatment plants, and crop fertilizationtechniques be made more efficientso as not to allow so many nitrates into thewater supply.They have begun to mark off areasaround wells and springs that should be regulatedto protect the water.