Nonylphenols (NPs), from its name you can guess it is a phenol that has a nine-carbon chain attached to it. Therefore, NPs are a family of alkylphenol and the alkyl chain can be attached to any position of the phenol. Among all the isomers, a branched 4-nonylphenol is the most widely used NP. The largest industry application for 4-NP is in the manufacture of nonionic surfactants due to the stability, excellent wetting, emulsifying property of 4-nonylphenol ethoxylate (4-NPE). Those nonionic surfactants have been used in commercial and household cleaning products, such as detergents, shampoos, lotions, liquid cosmetics. The other area of their application includes used as antioxidant, corrosion inhibitors, pesticides, chemical and heat stabilizers.
NPs are known to be very toxic to wildlife, particularly aquatic organisms. Like well-publicized bisphenol A, NPs exhibit estrogenic effects in the body. This type of compound is classified as an endocrine disruptor which usually functions by mimicking hormone through its binding with an estrogen receptor and acting competitively against natural estrogen. NP's hormone-like effect was first discovered by accident when it was found that existence of NP contaminated the experiment results conducted with natural estrogen. The subsequent researches have shown NPs can displace the estrogen in a fish from its receptor. Male fish exposed to NPs has resulted in lower testicular weight. The other effects of NPs include feminization of fish, reduction of male fertility.
Due to their physical–chemical characteristics, such as low solubility and high hydrophobicity, NPs accumulate in environmental compartments. NPEs degrade into NPs when they reach sewage treatment facilities. Besides of sewage sludge, NPs are also found in other matrices such as effluents from sewage treatment, river water and sediments, soil and groundwater. Because many NPs containing products used for cleaning have down-the-drain application, they are handily and frequently introduced into the water supply. NPs are however not readily biodegradable. Their half-lives in sediment are estimated to be more than 60 years. So, the sewage sludge if being recycled into agricultural land will result in contamination to the crops from which they are grown. NPs' other environmental impacts include feminization of aquatic organisms, decrease in male fertility and the survival of juveniles at a concentration as low as 8.2 μg/l. Due to their harmful effects, the use and production of NPs have been banned in EU countries and strictly monitored in many other countries such as Canada and Japan. In 2005, EPA set Ambient Water Quality Criteria (AWQC) for NPs for fresh water (FW) and salt water (SW) as below:
AWQC, FW one-hour average 28 ug/L
AWQC, FW four-day average 6.6 ug/L
AWQC, SW one-hour average 7 ug/L
AWQC, SW four-day average 1.7 ug/L
These criteria are not to be exceeded more than once every 3 years.
In 2014, EPA proposed a significant new use rule (SNUR) that will require the manufacturer to submit to EPA for review whenever the use of any of the 15 NPs and/or NPEs is started or resumed.
In our lab, we have developed a method using GC-MS to analyze NP with a detection limit of 2.22 ug/L. We are among the few labs with the capability to test this parameter. If you have any questions about this testing, please feel free to contact us.