Saturday, Feb. 23, 2008 | Steve Bay, a toxicologist at the Southern California Coastal Water Research Project in Costa Mesa, has helped lead an on-going study examining the effects that chemical contaminants have on marine life near the coast, including San Diego’s waterfront. Scientists involved in the large research effort have sampled some 600 fish, measuring their chemistry, in addition to the contents of ocean sediment and treated effluent from wastewater outfalls.
The research could help answer a significant question: How concerned should the public and policymakers be about the discharge of chemicals, including pharmaceuticals, into the ocean through treated wastewater? It’s a relevant question in the city of San Diego, where Mayor Jerry Sanders has begun the process of seeking another waiver of federal treatment standards for the wastewater dumped in the ocean from the Point Loma Wastewater Treatment Plant.
The research has focused on coastal fish collected from Point Loma north to Santa Monica Bay and has attracted attention because some fish have shown higher levels of estrogen than expected and they have exhibited a repressed response to stress. What remains uncertain is why: Whether it’s a natural phenomenon or a chemically altered state.
We interviewed Bay via e-mail to ask about his research, what he’s learned from studying contaminants in the ocean and how the contents of sewage serve as a mirror to the urban existence.
At a macroscopic level, the sewage discharged into the ocean seems one-dimensional: It’s poop — without quite as much stuff in it. Tell us what you find when you examine sewage at the microscopic level.
Sewage is not discharged into the ocean. Sewage refers to the stuff in the sewer system that enters the treatment plant for treatment; it is very different from the treated municipal wastewater effluent discharged into the ocean.
Sewage is actually more than just poop, it’s a mixture of all sorts of waste from just about everything that a city does. It includes your dirty dishwater and laundry detergent, and anything that goes down the drain from retail and manufacturing businesses in the city.
It’s really a reflection of a day in the life of a city. The treated wastewater is also a very complex mixture of compounds and some particles that remain after treatment. Most of the chemical compounds are oils and greases from foods and various types of nitrogen and phosphorus compounds, which can be nutrients to plants. The effluent also contains much lower concentrations of a wide variety trace constituents, such as metals, industrial chemicals, and chemicals used in pharmaceuticals, personal care products, and household items.
How concerned should we be about the number of chemicals that we’re discharging into the ocean?
This is one of the most difficult questions that scientists, regulatory agencies and the public are trying to answer. We have large gaps in our information about the types and effects of these chemicals on ocean life, so the answer is uncertain at this point. Recent monitoring data in Southern California finds little evidence of impacts on the populations of the fish and other organisms living near these discharges, so the evidence suggests that local effects are small.
However, we still don’t have complete information on what chemicals are discharged, where they end up in the ocean, and whether these chemicals interact with each other in unexpected ways, so we can’t give a definitive answer. The impacts of these discharges also depends on the environmental setting; the ocean discharges of wastewater receive much more dilution than most inland discharges, which reduces the exposure of organisms to chemicals in the effluent.
Some of the effects that you’ve reported on recently have been found in fish throughout the region, not just around the outfalls; how can this be a response to the discharge of chemicals?
We have found unusual patterns in some fish hormones, both at the reference site used in our study and at sites near the outfalls. We expect females to have more estradiol (the fish estrogen) than the males. But in the hornyhead turbot, the males have higher or equal levels of estradiol. That’s one pattern that endocrinologists haven’t seen before.
Another hormone measured is cortisol, it’s a hormone produced in response to stress. So when an animal is threatened, they should be producing high levels of that. What we find in these fish, they don’t respond as strongly to the stress of being caught in trawl nets. They have a repressed stress response. It’s something we find in fish from many locations around here.
We don’t yet know the reason behind these findings, but there are several hypotheses. First, it is possible that these patterns, though unexpected, are actually within the normal range for the fish we are studying. A second hypothesis is that the results indicate a response to widespread chemical exposure. Some of the chemicals of concern, such as DDT, are dispersed throughout Southern California waters and are detected in fish over a wide area. We are currently planning additional research to analyze fish from even more remote areas, which should help understand what these findings mean. One of the difficulties in studying the effects of contaminants on fish from the wild is that we often don’t know important aspects of the biology of the fish and their ability to move throughout the study area makes it difficult to interpret the results with respect to specific locations.
Is there any research that tells us what the predominant origin of the chemicals and other substances found in the ocean is? Whether municipal wastewater, storm-water runoff or industrial discharge?
It really depends on the specific chemical. Thirty years ago, municipal wastewater effluent was the dominant source of many of the contaminants of concern into the ocean, such as metals, pesticides, and industrial compounds. Regulations, source control, and improved sewage treatment have resulted in tremendous reductions of the effluent chemical loads. As a result, other sources, including urban runoff and atmospheric deposition are now equivalent, or even greater, sources of many of these contaminants. Runoff discharges are not treated, so the chemical inputs from this source have increased as the population of coastal Southern California has soared. There is much less data available for pharmaceuticals, but we expect that municipal wastewater and agricultural discharges are major sources.
If significant levels of flame retardants and other chemicals are being found in the ocean and coming from our sewage, what does that say about our internal chemistry?
These data don’t tell us much about our internal chemistry, other than we take a lot of medications to get through our day. Some of the industrial and commercial compounds like flame retardants likely end up in the sewage from sources other than human waste, such as manufacturing or laundry.
A lot of attention has focused on the levels and effects of estrogen found in fish in the ocean — particularly those surrounding wastewater outfalls. Is this the leading substance of concern? Can you single out one persistent chemical or pharmaceutical as the most potentially troublesome?
We think that the estrogen found in these fish is natural, not the result of estrogen discharged in municipal wastewater. Regarding chemicals of greatest concern, we can’t answer this question yet, especially for Southern California. Part of the difficulty is that the fish are potentially exposed to many contaminants at the same time, including those from historical discharges such as DDT and PCBs, and other factors such as fishing and ocean temperature can affect their populations. A focus of our current research is trying to sort out these issues.
Can you explain how something like estrogen affects a fish’s internal biology?
Estrogen, like other hormones produced by the fish, can affect many different aspects of the fish’s physiology by controlling the expression of genes and chemical reactions. Generally, the hormone circulates in the blood and then binds to special receptors on cells in various tissues. When the hormone binds to the receptor, it can trigger actions such as turning on specific genes or changing the rate of a reaction. For example, when fish liver cells are exposed to increased levels of estrogen, they are stimulated to produce more of a protein called vitellogenin. This protein is then transported by the blood to the ovary, where it is used to make the yolk in fish eggs. The increased production of vitellogenin in male fish is one of the indicators that toxicologists use to determine whether these fish are exposed to chemicals that have estrogen-like characteristics.
Is there a point at which male fish begin to exhibit so many female characteristics that they’re unable to reproduce? Is the question of their sex black-and-white? Or is there some chemically altered in-between hermaphroditic state in which you find them?
We haven’t yet found conclusive evidence of reproductive failure in Southern California. Other researchers have conducted laboratory experiments and have found that the reproduction of fish can be inhibited to various degrees, depending on the dose of chemicals they get. The response depends on both the concentration of the chemical and sensitivity of the particular fish species. It is rarely a black-and-white response that is easy to interpret. Interestingly, changing sex is a natural occurrence for some fish, like the California sheephead; so finding an “in between” specimen is not always a sign of a problem.
If you could have one major scientific question answered — one mystery about chemical loads and marine life solved — what would it be?
I’d like to be able to communicate directly with the fish and other marine life. If we could get them to tell us where they were last week, what they ate yesterday, do they feel sick and whether they had sex recently, then we would have a much better understanding of the effects of contaminants on them.
Can you describe where scientists currently are in understanding the implications and extent of the chemical load being discharged offshore? Is the science on this emerging because of the proliferation of pharmaceuticals and chemicals or are other reasons afoot?
We have made a lot of progress since the 1970s, when scientists began to study these issues in detail. Monitoring of the fish and other animal communities locally documented areas of impact in harbors and some offshore areas in the 1970s, but we didn’t have good information on the loads or sources.
We now have over three decades of monitoring data which describes the amounts and major sources of the contaminants of greatest concern, things like DDT, PCBs and trace metals. Areas of impact related to waste discharges have also declined substantially over time and show some correspondence with reductions in chemical loads in offshore discharges.
We have only recently developed the analytical tools needed to measure the concentration and potential effects of the wide variety of other chemicals discharged into the marine environment, like pharmaceuticals, flame retardants and plastic additives. Our understanding of the fate and effects of these types of chemicals is emerging because we have been investigating them for only a short time and many significant data gaps remain.