Fractionated algal organic materials as precursors of disinfection by-products and mutagens upon chlorination.

Cells and proteins of Chlamydomonas sp. (a common green alga in local reservoirs) were separated by ultrafiltration respectively into 3 fractions with variable molecular weights (MW: >100, 10-3 and <3 kDa). After chlorination (20°C, pH 7, Cl(2)/DOC ratio of 20 mg Cl(2)mg(-1), 120 h), levels of disinfection by-products (DBPs) and mutagenicity (via Salmonella T100 mutation assay, -S9) were analyzed. The highest yields of chloroform (2571 µmol mol C(-1)), DCAA (19,083 µmol mol C(-1)) and TCAA (4939 µmol mol C(-1)) were observed from the fraction of MW>100 kDa, while the fraction of 3-10 kDa was potent DCAN precursor. In contrast, the chlorinated MW 3-10 kDa cell fraction showed high mutagenicity (maximum level of 93 rev µL(-1) at 2 min), while the MW>100 kDa cell fraction showed low mutagenicity (maximum level of 16.6 rev µL(-1) at 7200 min) after chlorination. This indicated that unmeasured DBPs or possible interactions among the DBPs contributed to the mutagenicity. Comparing between the cell and protein fractions, the former was more potent in forming chloroform, DCAA, TCAA, DCAN and TCAN. This is the first study that fractionated algal cells and proteins were examined for DBP formation and mutagenicity.

Algal-derived organic matter as precursors of disinfection by-products and mutagens upon chlorination.

Algal-derived organic materials (including algal cells, hydrophilic and hydrophobic proteins) from Chlamydomonas sp. (a common green alga in local reservoirs), were chlorinated in the laboratory (20 °C, pH 7, Cl(2)/DOC ratio of 20 mg Cl(2) mg(-1)). Levels of disinfection by-products and mutagenicity (via Salmonella T100 mutation assay, -S9) over 2 h of chlorination time were determined. The hydrophilic proteins were more effective precursors of chloroform (35.9 µmol L(-1) at 120 min), 35 times greater than that from the hydrophobic proteins; whereas the hydrophobic proteins were more potent precursors of direct-acting mutagens (maximum level of 50.1 rev µL(-1) at 30 s) than the hydrophilic proteins (maximum level of 3.38 rev µL(-1) at 60 min). The mutagenicity of the chlorinated solutions generally reached a peak level shortly after chlorination and then declined afterwards, a pattern different from that of chloroform generation. The results indicate that algal hydrophilic proteins, containing low aromaticity and difficult to be removed via coagulation/flocculation, are important chloroform precursors. It is also suggested that hydrophobic organic intermediates with low molecular weight formed during chlorination may serve as the direct-acting mutagens.

Severe cow's milk protein allergy in a Chinese neonate.

Cow's milk protein allergy is a growing problem in developed countries. We report the case of a Chinese infant, born at term, who presented on day 28 with severe growth failure, chronic diarrhoea, and metabolic acidosis. Investigations supported a diagnosis of cow's milk protein allergy. This was confirmed by withdrawing and reintroducing the relevant infant formula under controlled clinical conditions. Both acidosis and diarrhoea were seen to resolve, and 'catch-up' growth was evident after introduction of an elemental infant formula. Early recognition of this problem leads to a rapid 'cure', as seen in this case. However, later presentation with other atopic conditions has been reported.