Wastewater irrigation: the state of play

As demand for fresh water intensifies, wastewater is frequently being seen as a valuable resource. Furthermore, wise reuse of wastewater alleviates concerns attendant with its discharge to the environment. Globally, around 20 million ha of land are irrigated with wastewater, and this is likely to increase markedly during the next few decades as water stress intensifies. In 1995, around 2.3 billion people lived in water-stressed river basins and this could increase to 3.5 billion by 2025. We review the current status of wastewater irrigation by providing an overview of the extent of the practice throughout the world and through synthesizing the current understanding of factors influencing sustainable wastewater irrigation. A theme that emerges is that wastewater irrigation is not only more common in water-stressed regions such as the Near East, but the rationale for the practice also tends to differ between the developing and developed worlds. In developing nations, the prime drivers are livelihood dependence and food security, whereas environmental agendas appear to hold greater sway in the developed world. The following were identified as areas requiring greater understanding for the long-term sustainability of wastewater irrigation: (i) accumulation of bioavailable forms of heavy metals in soils, (ii) environmental fate of organics in wastewater-irrigated soils, (iii) influence of reuse schemes on catchment hydrology, including transport of salt loads, (iv) risk models for helminth infections (pertinent to developing nations), (v) microbiological contamination risks for aquifers and surface waters, (vi) transfer efficiencies of chemical contaminants from soil to plants, (vii) health effects of chronic exposure to chemical contaminants, and (viii) strategies for engaging the public.<br /

On the Twin Risk in Autism

Autism is considered by many to be the most strongly genetically influenced multifactorial childhood psychiatric disorder. In the absence of any known gene or genes, the main support for this is derived from family and twin studies. Two recent studies (Greenberg et al. 2001; Betancur et al. 2002) suggested that the twinning process itself is an important risk factor in the development of autism. If true, this would have major consequences for the interpretation of twin studies. Both studies compared the number of affected twin pairs among affected sib pairs to expected values in two separate samples of multiplex families and reported a substantial and significant excess of twin pairs. Using data from our epidemiological study in Western Australia, we investigated the possibility of an increased rate of autism in twins. All children born between 1980 and 1995 with autism, Asperger syndrome, or pervasive developmental disorder not otherwise specified (PDD-NOS) were ascertained. Of the 465 children with a diagnosis, 14 were twin births (rate 30.0/1,000) compared to 9,640 children of multiple births out of a total of 386,637 births in Western Australia between 1980 and 1995 (twin rate weighted to number of children with autism or PDD per year 26.3/1,000). These data clearly do not support twinning as a substantial risk factor in the etiology of autism. We demonstrate that the high proportion of twins found in affected-sib-pair studies can be adequately explained by the high ratio of concordance rates in monozygotic (MZ) twins versus siblings and the distribution of family size in the population studied. Our results are in agreement with those of two similar studies by Croen et al. (2002) in California and Hultman et al. (2002) in Sweden

Association of sociodemographic characteristics of children with intellectual disability in Western Australia

The social determinants of intellectual disability (ID) are poorly understood, particularly in Australia. This study has investigated sociodemographic correlates of ID of unknown cause in Western Australian born children. Using record linkage to the Western Australian Maternal & Child Health Research Database, maternal sociodemographic characteristics of children with ID (of unknown cause) born between 1983 and 1992 (n=2871) were compared with those of children without ID (n=236,964). Socioeconomic indices for areas based on the census district of mother's residence were also included in the analysis. Aboriginal mothers (OR=2.83 [CI: 2.52, 3.18]), teenagers (OR=2.09 [CI: 1.82, 2.40]) and single mothers (OR=2.18 [CI: 1.97, 2.42]) were all at increased risk of having a child with mild or moderate ID. Children of mothers in the most socioeconomically disadvantaged 10% had more than five times the risk of mild and moderate ID compared with those in the least disadvantaged 10% (OR=5.61 [CI: 4.42, 7.12]). Fourth or later born children were also at increased risk (OR=1.82 [CI: 1.63, 2.02]). The results of the study have implications both for further aetiological investigation as well as service provision for children with ID. Furthermore, many of the sociodemographic correlates identified in this study, particularly in the mild/moderate category of ID, are potentially modifiable, opening up opportunities for primary prevention.Intellectual disability Sociodemographic determinants Epidemiology Mental retardation Australia