The Science Programme

Reprotoxic effects of benzene

In 2005, the European Commission completed an extensive review of benzene's health and environmental effects under its existing substances regulation. During the course of this work, two articles were identified that appeared to indicate that benzene may have adverse effects in the offspring of exposed rats. Because the findings were unique and had not been encountered in other similar studies, Professor Richard Irons, the leading world authority on the biology of benzene, was asked to provide a review of the significance of these findings in the context of current understandings of the molecular biology of benzene. Professor Irons findings demonstrate that whilst benzene has many toxic properties, it is no more toxic to the offspring for children than to adults. These same conclusions were also reached by the EU. More info: Click here

Biodegradability of benzene

It is important that an accurate understanding of a substance's biodegradability in the environment is available in order that suitable judgements can be made on the nature of controls that may be necessary to reduce any emissions. Over the past 30 to 40 years, several studies have been undertaken on the biodegradation of benzene. Unfortunately, many of these testing methods are not of an acceptable quality today. This has meant that interpreting the findings of the studies has been very difficult as, in some cases, the results are conflicting.

In view of the importance of having a sound understanding of benzene's biodegradability, a series of tests were performed by a number of laboratories. Three laboratories performed five different tests in order to ensure that minor variations in the testing protocol would be accounted for in the resulting test data. The results show that benzene is readily biodegradable in the environment. More info: Click here

The significance of the Morris Water Maze Test

The Morris Water Maze Test (MWMT) is a test that is been developed to help try to understand how drugs and similar substances may affect a person's memory. In the MWMT, rats swim in a pool which contains a simple maze. Within the maze are a series of platforms that the rat is able to climb on to. The rats' swimming performance is observed with or without administration of the drug, in order to investigate the effect of the drug.

Recently, the test has been used to evaluate whether solvents may have similar effects to drugs. Certain articles have been published on the topic. APA commissioned Dr Sandra Allen, a specialist in the field,to review the relative strength and weaknesses of the MWMT, particularly as it applies to materials other than pharmaceuticals. Dr Allen's report has been published in the literature. A summary of the report is available. More info: Click here

Fate of benzene in waste water treatment plants

It is important to demonstrate the effectiveness of control technologies used for the treatment of any benzene that is released from the aqueous effluent of aromatic production facilities. In Europe, most emissions from production facilities are predicted using mathematical models. Although these models may be accurate in many cases, they are not a substitute for real data.

A study was commissioned from a US leading company of environmental engineers and scientists (Hydroqual)to review the information that is available on the real life fate of benzene in waste water treatment plants (which are installed at production facilities to ensure that any benzene is effectively removed). They were asked to answer a specific question: what is the reason for the measured outlet concentrations of benzene at aromatics production plants being so low? One explanation may be that benzene is evaporated to air during the course of treatment. Another reason may be the fact that the micro-organisms in the treatment plant are particularly effective at digesting benzene.

Reassuringly, the answer is the latter. Waste water treatment plants that are associated with aromatic production plants and have become "acclimatised" to benzene are extremely efficient at removing benzene from waste water. So, the reason that so little benzene is found at the outfall is a result of the voracious appetite of these micro-organisms and not to the fact that it has been lost to air during the course of treatment. More info: Click here

Toxicity of benzene to algae

Although benzene is a substance for which much environmental information is available, some of the information is now more than 20-30 years old and, as such, no longer meets the standards expected of current laboratory tests. Therefore, a laboratory test was commissioned to ensure that a current OECD test was available to inform any decisions which need to be made in this area. The study demonstrates that benzene is of low toxicity to algae. More info: Click here

Ecotoxicological database for xylenes

APA is committed to ensure that the database supporting its products is the best available. It recognised that several of the studies that describe the effects of xylenes in the environment were not to present day requirements. Therefore, it sought to ensure the database contained relevant, high quality data. After a general call for tender, TNO has been chosen to perform the following tests on para-xylene according to the OECD protocols.

Determination of the effect of p-xylene (CAS#106-42- 3) on the growth of the fresh water green alga Selenastrum capricornutum (OECD Guideline No. 201).

The differences between the observed effect that xylene had on algal growth rate and growth under the test conditions are not indicative of toxicological relevance. More info: Click here

Daphnia Magna reproduction test with p-xylene

The data processing showed a No Observable Effect Level at 1.57 mg/l. More info: Click here

Screening of the effect of p-xylene (CAS# 106-42-3) on the respiration of activated sludge (OECD Guideline No. 209)

It was concluded that no inhibition of the respiration rate of activated sludge took place at the limit concentration of p-xylene (water saturation). More info: Click here

Information on emissions from aromatics production facilities

Information on the nature of emissions to the environment from production facilities was collected by APA in the 1990s, and this has been updated in 2005. APA gathered information from all its member companies, enabling a full assessment of the nature of human and environmental exposures. The exercise was performed by an independent institution, the Royal Haskoning laboratories in the Netherlands who are experienced in these fields and have advised the Commission and governments on this task.