The San Francisco Estuary Institute and aquatic sciences Center hosted this data challenge where participants were encouraged to produce a data visualization that is easy interpretable by a general public audience and addressed how contaminants in the SF Bay affect the toxicity of local fish. This post is a summary of my submission for the challenge.
Pamphlet Inside
Pamphlet Outside
The Challege: "Imagine you are a public health official in the Bay Area. For public outreach efforts, you need data on where and what types of fish caught in San Francisco Bay are less safe to eat." *as described on the SFEI challenge announcement
Question 1: Which fish species are of greatest or least concern to eat?
Previous studies have reported high concentrations of Mercury, Chlordanes, DDTs, PBDEs, and PCBs in fish tissues sampled along the California coast (Hose et. al. 1989, EPA 2007, Klasing and Brodberg 2008, Parnell 2008, Sanchez 2015). These toxins are also reported to impact human immune, renal, cardiovascular, endocrine, and neurological health and development (ATSDR 1998-2004). In efforts to evaluate the accumulation of these toxins in fish in the San Francisco Bay. I filtered data from the publicly accessible database of contaminant data provided by the San Francisco Estuary institute. From this dataset, I used the following analytes under the “Tissue” test material where organism was “Fish”: “Mercury”, “Sum of Chlordanes”, “Sum of DDTs”, “Sum of PBDEs”, and “Sum of PCBs.” To prepare the data, I first filtered the database for only samples of fish tissues collected within areas of the bay where the column “Baysegment_name” was defined. I then converted the units of all measurements into ng/g for ease of comparison. Each sample in the database was an average of several fish, therefore I further edited the data to avoid calculating an average of averages. Specifically, I multiplied each sample by the number of fish used in the sample, recorded the sum of contaminant measurements for each species and then divided that sum by the total number of individuals of that species observed in the database. From this data I produced two figures, one which shows the comparison of mercury concentration among species and a second which provides a comparison of the other toxin concentrations. I separated these two figures as Mercury was orders of magnitude greater in some fish tissues than the other toxins I compared. Interestingly, I found that almost all species considered had levels of one or more toxins which are unsafe for consumption if an average sized filet was consumed daily, or in some cases even weekly. The most concerning species are those with the highest toxin concentration including leopard sharks, brown smooth-hound sharks, white croaker, striped bass, and white sturgeon. In efforts to make this information accessible to the members of the public most likely to be affected by toxic contamination from consumption of fish, I chose to compile my figures into a pamphlet with a protective pocket for fishing licenses. I felt that a pamphlet with protective pocket was the perfect size for most recreational fishermen to store in their tackle boxes.
Question 2: Is there any relationship/correlation between fish tissue PCB or mercury concentration and concentrations of other chemicals in fish tissue?
From the results of my figures in question 1, I found that aside from Mercury, PCBs were the toxin of highest concentration for many species tested. I also noticed that species with high PCB concentration appeared to have higher concentrations of other toxins as well. High toxin concentration in fish has been demonstrated to cause diminished growth rates, deformation, developmental irregularities, and reproductive defects (Lema et. al. 2007, Jezierska et. al. 2009, Skandhan et. al. 2011). These abnormalities are cause for concern in fished species as stock replenishment is highly reliant on healthy fish reproductive systems and development in juvenile fish to adulthood. To assess if there were detectable relationships among PCB concentrations and other toxins analyzed, I used the same dataset I generated for question 1, where for each species I calculated the average toxin concentration of PCBs, chlordanes, DDTs, and PBDEs and Mercury. I ran correlation tests (in the statistical analysis program R) comparing PCB concentration in fish tissues to concentrations of the other measured toxins in fish tissues. In three cases there was a significant correlation such that the abundance of chlordanes (P: 0.003, r: 0.89), DDTs (P: 0.001, r: 0.93), and PBDEs (P:0.046 r: 0.82) all increased linearly with an increase in PCBs. Mercury and PCBs concentrations were uncorrelated (P: 0.683). I then generated a figure which demonstrated the relationships of PCBs with chlordanes, DDTs, and PBDEs (fig. 3). From the correlation coefficients of these relationships we can see that in all three cases a high proportion of the variation in the toxin concentration among species can be explained by the concentration of PCBs. This is a useful relationship to be aware of, as it may be indicative that if it is known that PCB concentration is high in a given species it can be deduced that that species is likely to also have high concentration of other chemicals as well. A list of all of the species tested for both questions 1 and 2 can be found on the first back panel of my pamphlet (described in question 1). In efforts to highlight the trends in figure three I wrote a short descriptive summary of the figure, placed immediately above it on the pamphlet. My hope is that a pamphlet like this could be handed out when fishing licenses are purchased at stores for fishermen to have a clear understanding of potential contamination in their catch.
References
ATSDR. 1998. Public Health Statement: Chlordanes. Agency for Toxic Substance and Disease Registry, Division of Toxicology and Human Health.
ATSDR. 1999. Public Health Statement: Mercury. Agency for Toxic Substance and Disease Registry, Division of Toxicology and Human Health.
ATSDR. 2000. Public Health Statement: Polychlorinated Biphenyls (PCBS). Agency for Toxic Substance and Disease Registry, Division of Toxicology and Human Health.
ATSDR. 2002. Public Health Statement for DDT, DDE, and DDD. Agency for Toxic Substance and Disease Registry, Division of Toxicology and Human Health.
ATSDR 2004. Public Health Statement: Polybrominated Diphenyl Ethers (PBDES). Agency for Toxic Substance and Disease Registry, Division of Toxicology and Human Health
EPA. 2007. Fish Contamination in Southern California. In: California EPA, Office of Environmental Health Hazard Assessment. Sacramento, CA. Pages 1–4.
Hose, J.E., J.N. Cross, S.G. Smith, and D. Diehl. 1989. Reproductive impairment in a fish inhabiting a contaminated coastal environment off Southern California. Environmental Pollution 57:139–148.
Jezierska, B., Ługowska, K., & Witeska, M. (2009). The effects of heavy metals on embryonic development of fish (a review). Fish physiology and biochemistry, 35(4), 625-640.
Klasing, S., and R. Brodberg. 2008. Development of fish contaminant goals and advisory tissue levels for common contaminants in California sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene. OEHHA, Sacramento, CA. Pages 1–122.
Lema, S. C., Schultz, I. R., Scholz, N. L., Incardona, J. P., & Swanson, P. (2007). Neural defects and cardiac arrhythmia in fish larvae following embryonic exposure to 2, 2′, 4, 4′-tetrabromodiphenyl ether (PBDE 47). Aquatic toxicology, 82(4), 296-307.
Parnell, P. E., Groce, A. K., Stebbins, T. D., & Dayton, P. K. (2008). Discriminating sources of PCB contamination in fish on the coastal shelf off San Diego, California (USA). Marine pollution bulletin, 56(12), 1992-2002.
Sanchez, B. (2015). Effects of organic pollutants on the growth, condition, and reproduction of Paralabrax nebulifer (barred sand bass) in Southern California (Doctoral dissertation, California State University, Northridge).
Skandhan, K. P., Khan, P. S., & Sumangala, B. (2011). DDT and Male Reproductive System. Environmental Toxicology, 5(2), 76-80.