Background, aim, and scope Many pollutants have received significant attention due to their potential estrogenic effect and are classified as endocrine disrupting compounds (EDCs). Because of possible ecological effects and increased attention for water reuse schemes, it is important to increase our understanding of the EDC removal capacities of various wastewater treatment systems. However, there has so far been little research on the fate and behavior of EDCs in stabilization pond systems for wastewater treatment, which represent an important class of wastewater treatment systems in developing countries because of their cost-effectiveness. The aim of this work is to study the fate and behavior of EDCs in algae and duckweed ponds. Because the synthetic hormone 17α-ethinylestradiol (EE2) and the natural hormones estrone (E1), as well as 17β-estradiol (E2), have been detected in effluents of sewage treatment plants and been suggested as the major compounds responsible for endocrine disruption in domestic sewage; E1, E2, and EE2 were therefore chosen as target chemicals in this current work. Materials and methods Both batch tests and continuous-flow tests were carried out to investigate the sorption and biodegradation of estrogens in algae and duckweed pond systems. The applied duckweed was a Lemna species. The applied algae was a mixture of pure cultures of six different algae genera, i.e., Anabaena cylindrica, Chlorococcus, Spirulina platensis, Chlorella, Scenedesmus quadricauda, and Anaebena var. Synthetic wastewater were used in all tests. The concentrations of estrogens were measured with three different enzyme-linked immunosorbent assay kits specific for E1, E2, or EE2. When the concentrations of estrogens in water samples were below the lowest quantitative analysis range (0.05 µg/l), preconcentration of the water samples were performed by means of solid phase extraction (SPE) with C18 cartridges. Results The 6-day batch tests show that the presence of algae or duckweed accelerated the removal of the three estrogens from the synthetic wastewater. More estrogens were removed in the tests with duckweed than in tests with algae or with wastewater. In the sorption tests, a swift sorption of the three estrogens was observed when the estrogens were contacted with duckweed or algae, while the estrogen concentrations in tap water kept unchanged during the 3-h sorption tests. The mass balances indicated that only about 5% of the estrogens were bound to the algae sediment or duckweed at the end of the 6-day tests. Results of the continuous-flow tests revealed that the algae and duckweed ponds effectively removed E1, E2, and EE2 even at nanograms per liter level. Interconversion of E1 and E2 occurred both in batch and continuous-flow tests. E2 could be readily transformed to E1, especially in the tests with algae. Discussion Different processes like sorption, biodegradation and photolytic degradation might play an important role in the removal of estrogens from the aquatic phase. The 3-h sorption tests support the importance of sorption for estrogen removal, in which a rapid initial sorption was observed over the first 2 min for E1/E2/EE2 to both duckweed and algae. In the 6-day batch tests, estrogens were sorbed by algae or duckweed during the early stage when algae and duckweed were contacted with the synthetic wastewater and the sorbed estrogens were further biodegraded by the microorganisms developed in the wastewater. The persistent estrogen concentrations in tap water, however, implied that no sorption, biodegradation, or photolytic degradation occurred in tap water under the specific experimental conditions. Under aerobic or anoxic conditions, E2 could be first oxidized to E1, which is further oxidized to unknown metabolites and finally to CO₂ and water. Under anaerobic conditions, E1 can also be reduced to E2. However, the interconversion might be much more complex especially in the tests with algae because both aerobic and anaerobic conditions occurred in these tests due to the variation of the dissolved oxygen concentration induced by the light regime. Conclusions This study shows that estrogens, E1, E2, and EE2, can be effectively removed from the continuous-flow algae and duckweed ponds even when their concentrations are at nanograms per liter level. The presence of algae and duckweed accelerate the removal of estrogens from the synthetic wastewater because estrogens can be quickly sorbed on duckweed or algae. The sorbed estrogens are subsequently degraded by microorganisms, algae, or duckweed in the wastewater treatment system. E1 and E2 are interconvertible in both duckweed and algae pond systems. E2 can be readily transformed to E1, especially in the tests with algae. Recommendation and perspectives Based on the tests performed so far, one can conclude that both sorption and biodegradation are important to the estrogens removal from stabilization pond systems for wastewater treatment. Further research using, e.g., radioimmunoassay is needed to investigate the biodegradation pathway of estrogens in algae and duckweed ponds.

Background and purpose In Pakistan, almost 70% of the population lives in rural areas. Ninety-four percent of households in rural areas and 58% in urban areas depend on biomass fuels (wood, dung, and agricultural waste). These solid fuels have poor combustion efficiency. Due to incomplete combustion of the biomass fuels, the resulting smoke contains a range of health-deteriorating substances that, at varying concentrations, can pose a serious threat to human health. Indoor air pollution accounts for 28,000 deaths a year and 40 million cases of acute respiratory illness. It places a significant economic burden on Pakistan with an annual cost of 1% of GDP. Despite the mounting evidence of an association between indoor air pollution and ill health, policy makers have paid little attention to it. This review analyzes the existing information on levels of indoor air pollution in Pakistan and suggests suitable intervention methods. Methods This review is focused on studies of indoor air pollution, due to biomass fuels, in Pakistan published in both scientific journals and by the Government and international organizations. In addition, the importance of environmental tobacco smoke as an indoor pollutant is highlighted. Results Unlike many other developing countries, there are no long-term studies on the levels of indoor air pollution. The limited studies that have been undertaken indicate that indoor air pollution should be a public health concern. High levels of particulate matter and carbon monoxide have been reported, and generally, women and children are subject to the maximum exposure. There have been a few interventions, with improved stoves, in some areas since 1990. However, the effectiveness of these interventions has not been fully evaluated. Conclusion Indoor air pollution has a significant impact on the health of the population in Pakistan. The use of biomass fuel as an energy source is the biggest contributor to poor indoor air quality followed by smoking. In order to arrest the increasing levels of indoor pollution, there is a dire need to recognize it as a major health hazard and formulate a national policy to combat it. An integrated effort, with involvement of all stakeholders, could yield promising results. A countrywide public awareness campaign, on the association of indoor air pollution with ill health, followed by practical intervention would be an appropriate approach. Due to the current socioeconomic conditions in the country, development and adoption of improved cooking stoves for the population at large would be the most suitable choice. However, the potential of biogas as a fuel should be explored further, and modern fuels (natural gas and LPG) need to be accessible and economical. Smoking in closed public spaces should be banned, and knowledge of the effect of smoking on indoor air quality needs to be quantified.

Background, aim, and scope Phosphorus loss from terrestrial to the aquatic ecosystems contributes to eutrophication of surface waters. To maintain the world's vital freshwater ecosystems, the reduction of eutrophication is crucial. This needs the prevention of overfertilization of agricultural soils with phosphorus. However, the methods of risk assessment for the P loss potential from soils lack uniformity and are difficult for routine analysis. Therefore, the efficient detection of areas with a high risk of P loss requires a simple and universal soil test method that is cost effective and applicable in both industrialized and developing countries. Materials and methods Soils from areas which varied highly in land use and soil type were investigated regarding the degree of P saturation (DPS) as well as the equilibrium P concentration (EPC₀) and water-soluble P (WSP) as indicators for the potential of P loss. The parameters DPS and EPC₀ were determined from P sorption isotherms. Results Our investigation of more than 400 soil samples revealed coherent relationships between DPS and EPC₀ as well as WSP. The complex parameter DPS, characterizing the actual P status of soil, is accessible from a simple standard measurement of WSP based on the equation [graphic removed] . Discussion The parameter WSP in this equation is a function of remaining phosphorous sorption capacity/total accumulated phosphorous (SP/TP). This quotient is independent of soil type due to the mutual compensation of the factors SP and TP. Thus, the relationship between DPS and WSP is also independent of soil type. Conclusions The degree of P saturation, which reflects the actual state of P fertilization of soil, can be calculated from the easily accessible parameter WSP. Due to the independence from soil type and land use, the relation is valid for all soils. Values of WSP, which exceed 5 mg P/kg soil, signalize a P saturation between 70% and 80% and thus a high risk of P loss from soil. Recommendations and perspectives These results reveal a new approach of risk assessment for P loss from soils to surface and ground waters. The consequent application of this method may globally help to save the vital resources of our terrestrial and aquatic ecosystems.