Introduction

Until the eighties, some issues linking human health to the environment focused on infectious diseases such as cholera and other gastrointestinal diseases resulting from improper management of wastewater. However, in recent decades, attention has also been directed to non-infectious diseases such as cancer and certain congenital problems induced by toxic compounds (Masters, 1991; CCA, 2007). The serious consequences of the improper disposal of hazardous waste were pointed out in various international events, such as poisoning by mercury and cadmium in Japan which had high economic costs in addition to serious health issues in the population. In Mexico, for example, contamination by chromium that had been disposed of in open dumps and discharged into wastewater in Tultitlan, State of Mexico between 1974 and 1977, caused serious health damages, raising awareness about the risk of exposing society to this type of waste (Sedesol and INE, 1993). Lead entered the environment through the combustion of gasoline –until its phasing-out in recent years- and its use in the manufacture of paints. Lead exposure in Mexico caused high blood levels of mercury in 40% to 88% of children from various communities (Romieu et al., 1994, 1995), which can affect growth and cause neurological and learning impairment.

A waste is considered hazardous depending on its corrosiveness, as is the case of strong acids and bases; reactivity, as in nitrates and alkaline metals; explosiveness, in the case of peroxides and chlorates; toxicity, as in cyanide, arsenic and their salts; flammability, as in alcohols and aromatic hydrocarbons; and infectious properties, as in the case of blood or infectious agents (Bueno et al., 1996).

The manufacturing industry is one of the main generators of hazardous waste in Mexico. Its major waste types include solid waste, used oil, liquid waste from processes, solvents and sludge. The mining sector, including oil extraction, ranks second produces mostly liquid waste from processes, sludge, slag and solids (Semarnap-INEGI, 1999; Semarnat, 2006). Biological and infectious waste, mainly from hospitals, clinics, laboratories and research centers, is generated in smaller amounts, but is nonetheless important.

Numerous studies have been carried out worldwide to establish, with greater certainty, the effects of various chemicals on human health. There is now sufficient evidence showing the relationship between health damage and exposure to toxic compounds present in hazardous waste (ATSDR, 2004). One way in which people and ecosystems are affected by hazardous waste poorly managed is through the contamination of both surface and ground water sources (Sedesol-INE, 1993; Semarnat, 2006). Diseases associated with exposure to hazardous waste include cancer, birth defects and kidney and liver damage (Díaz-Barriga, 1996; Ostrosky et al., 1996).

In response, several countries -including Mexico- have set forth regulatory instruments for managing these substances, taking into account their entire lifecycle, i.e. from production to final disposal, in a "cradle to grave" approach (Masters, 1991). The result is the standard known as NOM-052-ECOL-2005, which defines the features, identification procedure and a list of waste that are hazardous for the environment because of their toxicity; the Regulation of the General Law of Ecological Balance and Environmental Protection with regard to Hazardous Waste; the Unique Environmental License (LAU¹); the Annual Operation Card (COA¹) and the of Pollutant Release and Transfer Registry (PRTR¹); the General Law on Waste Prevention and Integrated Management, and a dozen of additional official standards (DOF, 2003; Semarnat, 2004 and 2006).

Issues associated with hazardous waste fall along two major lines: on one hand, the line dealing with sites contaminated with hazardous waste; on the other, the line focused on preventign the contamination of new sites. Thus, actions aimed to address these issues deal with both the identification and treatment of contaminated sites, and contamination prevention through regulatory (e. g. inspection visits to generators) and voluntary (e. g. environmental audits) instruments. In parallel, efforts have been made for creating the infrastructure necessary for the different aspects of proper waste management: storage, collection, transportation, storage, reuse, treatment, recycling, incineration and disposal (Semarnat-Profepa, 2003; CCA, 2007), and promoting actions to minimize generation volumes, promoting changes in production processes, product replacement or any other measure taken by the generating company prior to recycling, treating or disposing of waste (EPA-Sedesol, 1993; CMPL, 2004; FIPREV, 2004; GTZ, 2004).

¹ For its acronym in Spanish

References

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