C01029: Uptake of alkylphenols by crops
Tuesday 2 September 2003
This research project aims to examine the potential of detergent residues to enter the food chain following uptake by food crops treated with sludge.
Study Duration: January 2000 to March 2004
Contractor: Imperial College of Science Technology and Medicine, T.H. Huxley School of Environment, Earth Sciences and Engineering
Background
Alkylphenols (particularly nonylphenols) are residues from industrial and domestic detergents. Nonyl phenol ethoxylate is the most common detergent in use and inevitably enters urban wastewater where it is transferred to sewage sludge during sewage treatment processes. Some of these residues are only poorly degraded during sewage treatment and can therefore find their way into the environment following sludge application to agricultural land.
The aim of this project is to examine the potential of alkylphenols and their breakdown products to enter the food chain following uptake by food crops treated with sludge.
Research Approach
Human and animal exposure to chemicals which may be present in sewage sludge applied to agricultural land depends upon several factors, such as soil persistence, crop uptake, and metabolism by crops.
The project is therefore set as a phased study with five key objectives, first to identify the key chemicals involved and then to investigate their fate in soil and plant uptake, as set out below:
- Identification of principal breakdown products of the nonyl phenyl ethoxylates in sewage sludges;
- Determination of environmental and metabolic degradation rates in soils to identify compounds of concern, if any;
- Determination of the maximum potential uptake of these compounds by food crops;
- Field lysimeter and pot trial studies to evaluate crop uptake of alkyl phenols from contaminated soils; and
- Determination of the influence of soil characteristics on the uptake of these compounds by crops.
Results and findings
This research investigated the uptake of nonylphenols (NPs), which are potential endocrine disrupters, from sewage sludge into food crops.
Uptake of NPs from a hydroponic system was studied in broad beans, spring wheat and carrots. All three crops were found to uptake NPs to varying degrees from concentrate solution. The concentration of NPs was highest in the roots and shoots of all three crops. In soil experiments, NP was found to degrade more rapidly in a clay loam soil sample with low organic matter and low sand content, compared to three other soils examined. In lysimeter trials, an instrument designed to collect soil water, uptake of NP by crops was low compared to the hydroponic system and the concentrations showed little variation in different parts of the crops. Overall, the results are in line with previous studies and show that while NPs can enter some crops from sewage sludge, the amounts found in edible portions of the plant pose no risk for human health.
Dissemination information
The final report is available from the FSA Library and Information centre.
To obtain a copy, please contact the Enquiry Desk, Dr Elsie Widdowson Library and Information Services, Food Standards Agency ( tel: 020 7276 8181/8182 or email: library&info@foodstandards.gsi.gov.uk ).