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Published by socb, 2021-12-09 09:18:42

M. Toxics

Drivers & Stressors Condition of the bay human connections

M. Toxics

Persistent Toxics Have Declined Over Past 30 Years Kevin Cole / Creative Commons

Uncertainties Remain about Impact of Novel Contaminants

why it matters Persistent Organic Contaminants

Our society releases thousands of biologically active PAHs
chemicals into the environment. These compounds include Polycyclic aromatic hydrocarbons are principally derived from
medications, pesticides, industrial chemicals, and byproducts petroleum products or combustion of petroleum or other
of combustion, corrosion and wear, among others. Such organic materials. Transportation and industrial activity are
compounds are called toxic when they have negative impacts major sources.
on human health or the environment, especially if they have
negative effects at low environmental concentrations. PCBs
Polychlorinated biphenyls are chlorinated hydrocarbons that
By definition, toxic chemicals can harm living organisms, found a variety of industrial uses 50 years ago. Because
including humans, animals, plants, and microorganisms. of their toxicity, their use was phased out in 1979. Today,
Contaminants can have both severe short-term and subtle PCBs may be released when older products are improperly
long-term effects. Effects include mortality, neurological disposed of, or as a byproduct of poorly controlled burning of
impairment, developmental effects, impacts to metabolic plastics.
processes, increased risk of genetic mutations and cancer,
disruption of hormonal systems, and changes in behavior. Dioxins and furans
Toxic contaminants in the environment can affect success Dioxins and furans are not industrial products in their own
of individuals and species, thus altering composition of right, but byproducts of incomplete combustion of organic
ecological communities and ecosystem processes. matter and some industrial processes such as chemical
manufacturing and chlorine bleaching of pulp and paper.
Many organisms can concentrate persistent contaminants in
their bodies, increasing contaminant exposure to organisms Butyltins
who eat them. In marine food webs, that process can occur Tributyltin is a metal-organic molecule used in anti-fouling
repeatedly as predator becomes prey, in a process called paint on large ships. Because of its toxicity and persistence
“biomagnification”. Biomagnification means that even low in the marine environment, its use on smaller boats has
environmental levels of persistent contaminants can pose been phased out. In the marine environment, it breaks down
health risks to organisms (from osprey and seals, to humans) into related mono- and di-butyltins, so the group of related
who eat large, predatory fish. compounds are often studied together.

Industrial uses of many persistent contaminants (like DDT DDT Residues
and PCBs – See the sidebar for information on persistent DDT is well known as one of the more troublesome members
toxic compounds) were phased out in the 1970s and 1980s, of a class of pesticides known as organochlorines. Other
leading to reductions in environmental concentrations. members of this class include chlordane and lindane. Most or-
We see the effects of those bans in long-term trends in ganochlorine pesticides were banned decades ago because
levels of persistent contaminants in Casco Bay. Yet use of of their persistence in the environment. Like many organo-
less-persistent toxic chemicals (including novel industrial chlorines, DDT breaks down into closely related chemicals in
chemicals, modern pesticides, pharmaceuticals and the environment.
personal care products) has expanded. For many bioactive
compounds, relatively little is known about their persistence Benchmarks for risk assessment
or impacts in the marine environment.
A common way to evaluate risks associated with con-
29 casco BAY estuary partnership taminants in sediments is to compare concentrations to
published risk benchmarks, such as ERL and ERM:

• Effects Range Low (ERL) – A concentration below
which negative effects on marine organisms are
seldom observed.

• Effects Range Median (ERM) – A concentration at
which negative effects are about as likely as not.

condition of the bay M. Toxics

status & trends

Butyltins Dioxins and Furans Total PAHs Total PCBs DDT Residues

Persistent Organic Contaminants on the Decline in Casco Bay's SedimentsButyltins Total PCBs
Butyltins Dioxins and Furans Total PAHs DDT Res

Dioxins and FuranBsutyltinsTotal PAHDsioxins and FuTroatnasl PCBs Total PAHDsDT Residues Total PCBs

Butyltins Dioxins and Furans 1,000To.0tal PAHs Concentration (ppb) Total P1,C0B0s0.0Concentration (ppb) DDT Residues
1,000.0 10.0 1,000.0
Concentration (ppb) 1,000.0 2000 1990 Concentration (ppb) 0.1 Concentration (ppb) In 2016, CBEP released analysis of twenty years
10.0 10.0 of sediment data from dozens of sites around
10.0 10.0 Casco Bay. From 1990 to 2010, concentrations
0.1 of many groups of toxic organic contaminants in
0.1 the Bay’s sediments declined. (Note: The y-axis is
0.1 0.1 2010 on a log scale.) More recent sediments are less 201WI0enstneBrayBay
129019 I002n0ne0r0Bay contaminated than older sediments, which are EasWtesBtayBay
1990West Bay now buried. Changes in analytic methods made
2000E2a0s1t0Bay it impossible to detect low levels of PCBs and OuteErasBtayBay
2000Outer Bay pesticides in 2010, so recent trends are uncertain,
but continued declines are likely.
1990 2000 2010 2000 2010 2010 2010 1990 201WI0e2nst0ne0Br0ayBay 201WI0e2nst0ne0Br0ayBay 201WI0e2nst0ne0Br0ayBay InCnaepreBSaymall
1990 1990 2000 22000000 1990 2I0n1Cna0epreBSaymall 199E0asWtesBtayBay 199E0asWtesBtayBay 199E0asWtesBtayBay
OuteErasBtayBay OuteErasBtayBay OuteErasBtayBay
11999900 2C0a0p0eO 12uS9t0e19mr00allBay 2C0a0p0eO 12uS9t0e19mr00allBay 2C0a0p0eO 2uSt0e1mr0allBay

InCnaepreBSaymall InCnaepreBSaymall

Below ERL Between ERL and ERM Above ERM No Reference Defined

Below ERL Between ERL and ERM Above ERM No RBeefelorewncEeRDLefined Below ERL Between ERL and ERM Above ERM No Reference Defined

Between ERL andBEeRloMw ERL AboveBEeRtwMeen ERLNaonRdeEfeRrMence DefAinbeodve ERM No R

Sediment Contamination Tends to Be Highest Near Portland

Butyltins Dioxins and Furans Total PAHs Total PCBs DDT Residues

Since 1990,

Concentration (ppb) 1,000.0 contaminant levels

Inner Bay have varied across West Bay
West Bay
East Bay10.0 regions of the Inner Bay East Bay
Outer Bay Bay. (Note: The Outer Bay
Cape Small0.1 y-axis is on a log Cape
Inner Bay scale.) Several Small
West Bay contaminants
East Bay
Outer Bay tend to be highest
Cape Small
Inner Bay in the Inner Bay (near the Portland metropolitan
West Bay
East Bay area) or lowest in the Outer Bay and off of Cape
Outer Bay
Cape Small Small (in Phippsburg). However, levels of PAHs are
Inner Bay
West Bay high in the East Bay, perhaps because of historic
East Bay
Outer Bay
Cape Small
Inner Bay
West Bay
East Bay
Outer Bay
Cape Small

discharges of contaminants from industries along

Below ERL Between ERL and ERM Above ERM No Reference Defined the Kennebec and Androscoggin Rivers.

Almost All Metals Decreasing in Sediments

Many metals are toxic and all are persistent in the environment. As each poses different risks, they need to be assessed separately. Almost all metals are
decreasing in Casco Bay’s sediments. None were observed at levels above the ERM threshold, and thus levels are thought to pose limited risks to marine
organisms. Persistent elevated levels of arsenic reflect presence of natural sources in the Casco Bay watershed. Elevated mercury bay-wide reflects
atmospheric deposition.

METAL Above erl* never trend** Differences among regions of Casco Bay

Arsenic frequent Common uncommon rare P increasing decreasing
Nickel P
Chromium P No trend Cape Small < Other regions
Mercury P
Cadmium Cape Small < Other regions
Copper P
Lead P Cape Small < East Bay and West Bay
Silver
Zinc P No trend Cape Small < Outer Bay and West Bay < East Bay < Inner Bay
P
P Cape Small < Outer Bay < Other regions

No trend Cape Small < Outer Bay < Other regions

Cape Small < Other regions < Inner Bay

No trend Cape Small < Other regions < Inner Bay

Cape Small < Other regions; Outer Bay < Inner Bay

Iron*** N/A (No ERL) No trend Cape Small < East Bay and West Bay

Selenium N/A (No ERL) No differences.

* Rare: < 10%; Uncommon: < 25%; Common: <50%, Frequent > 50%. No metals were above ERM.
** Trend analysis based on robust regression, including non-detects.
*** Iron is widespread in soil and sediments and is functionally non-toxic.

STATE OF casco BAY 30

condition of the bay M. Toxics

Results from Casco Bay Sediment Sampling (1991-2011)

chemical group Most recent conditions (2010-2011) trends since 1991

Metals Generally below concentrations likely to be harmful* Mostly declining/stable**

PAHs Below concentrations likely to be harmful Decline since 2000-2002

PCBs Rarely detected Decline 1991 to 2002; likely continued through 2010***

Dioxins and Furans Low concentrations**** Decline since 2000-2002

Organochlorine Pesticides Rarely detected Decline 1991 to 2002; likely continued through 2010

Butyltins Low concentrations, often not detected Declining

*For those metals where sediment screening values are available. **Cadmium and silver show increases, but result could be due to differences in laboratory methods between
sampling events. ***Because of changes in laboratory methods, detection limits in 2010 and 2011 were relatively high, obscuring trends. ****ERL and ERM levels are not
available for dioxins and furans.

Deep Sediments of Portland Harbor Are More Contaminated

In 2018, the Portland Harbor Commission commissioned a study of contaminants in PAHs (ppb)

sediments of Portland Harbor. The study was undertaken as part of designing a “Confined < 4,022* Portland
Aquatic Disposal” facility to safely dispose of potentially contaminated dredged material 4,022 - 16,000† South
16,001 - 44,792† Portland

from the Harbor. The results provide a window into historic levels of contaminants in 44,793 - 150,000‡ Portland
> 150,000‡ South
the Harbor, bBuetcyltainus se saDmiopxinles asndwFuerarnes colleTcottael PdAHfsrom matTeotrailaPlCBbsuried uDnDdT eRersisdueevs eral feet of Portland
DDT Residues
sediment, which has accumulatBeutdyltionsver maBDuniotxyyilntisdnsaendcFaudraenDssio.xiTnshaenTdotdFaulePraeAnHpss sedTimotael TPnoAttHaslsPoCBfsthe HarborDDT Residues Portland
South
Total PCBs Portland

act 1a,00s0.a0 time capsule, Concentration (ppb) revealing levels of contamination that were commonplace in the
ConcentratiCoonn(cpepnbt)ration (ppb) Concentration (ppb)
1,000.0
harbor 50 years ago, before pass1,0a0g0.e0 of major environmental laws.

10.0 10.10,000.0 10.0 Right: The highest levels of PCBs (ppb)
100,000 < 4.0*
1990 contaminants were generally found 4.1 - 22.7*
0.1 22.8 - 100†
1,000 Concentration (ppm)0.1 along the Portland waterfront. That 100.1 - 180†
> 180‡
10 0.1 partially reflects the waterfront’s No data

Be1l0o.w0 ERL Below ERL industrial heritage but also decades

Between ERL and ERM Between ERL and ERM of runoff from the City and uncon-
I 2n0ne0r0Bay West Bay WIe2nst0ne0Br0ayBay WIe2nst0ne0Br0ayBay WIe2nst0ne0Br0ayBay InCnaepreBSaymall WIenstneBrayBay InCnaepreBSaymall
Above ERM East Bay Above ERMEasWtesBtayBay EasWtesBtayBay EasWtesBtayBay EasWtesBtayBay West Bay East Bay Outer Bay Cape Small
2010 OuteErasBtayBay OuteErasBtayBay OuteErasBtayBay OuteErasBtayBay
Outer Bay CapeO 2uSt0e1mr0allBay CapeO 2uSt0e1mr0allBay CapeO 2uSt0e1mr0allBay CapeOuStemrallBay
1990 2000 2010 1990 trolled wastes discharged directly
InCnaepreBSaymall 1990 1990
InCnaepreBSaymall InCnaepreBSaymall
0.1 to the Bay before construction of

wastewater treatment plants.

Total PAHs Total PCBs DDT ResiduesBelow ERL Between ERL and ERM Above ERM No Refere*nBceelowDeERfiLn(eedffects range low)
Below ERL
CADMIUM Between ERL and ERM † BeAtwbeoevneEERRLMand ERM No Reference Defined
MERCURY
Below ERL Between E‡ RAbLoavendEREMR(Meffects ranAgebmoveediaEnR) M No Reference Defined
ARSENIC
NICKEL DDTs (ppb)

CHROMIUM 1.6 - 2.5†
COPPER
LEAD
ZINC

Above: Levels of organic contaminants (left graph) were substantially higher than elsewhere in Casco Bay, and 2.6 - 5.0†
also higher than in shallow sediments from Portland Harbor. (Note: The y-axis is on a log scale.) Over half the 5.1 - 46.1†
samples had concentrations of PAHs at or above levels of concern. Levels of PCBs are less extreme, although 46.2 - 150‡
still higher than elsewhere in Casco Bay. DDT residues are consistently at levels of concern, an especially > 150.0‡

striking result, as the pesticide has been banned for decades, probably because of DDT’s long environmental

persistence and low mobility in the Harbor’s sediments. Levels of metals (right graph) in Portland Harbor deep

sediments regularly exceeded screening levels. Concentrations are often several times higher than seen in

Casco Bay’s shallow sediments. Levels for mercury, copper, lead, and zinc, regularly exceeded levels of concern.

Urbanized Shores Have Higher Levels of the Pesticide Bifenthrin

Many persistent toxic chemicals, including DDT and most other organochlorine 1.00 South Portland 2014
pesticides, were restricted or outlawed in the later part of the twentieth century. As 0.30
a consequence, levels of such persistent toxics have declined in the environment. Yarmouth 2014
Novel compounds, such as less persistent pesticides, have come to replace outlawed
or restricted chemicals in many uses. Replacement chemicals can pose lower Bifenthrin (ng/g)
environmental risk, but they are not risk-free, and many are less studied.

Because lobsters and other crustaceans may be vulnerable to certain pesticides, 0.10 Observed
Maine’s Board of Pesticides Control conducted studies of fourteen “pyrethroid”
pesticides, in Maine’s intertidal marine sediments in 2014 and 2015, including 18 0.03 Estimated
locations around Casco Bay. Only bifenthrin, which is relatively easy to detect at low 0 (Below Detection Limit)
concentrations, was detected regularly. Bifenthrin (first approved for use in the U.S. in
1985) was detected in most samples, although at levels well below levels of concern. 10 20 30 40

As shown in this graph, the levels of bifenthrin are related to urbanization. Higher Percent Impervious within 500 m
levels were observed when impervious surfaces like roads and parking lots were
common within 500 meters of the sampling location. The relatively high sample from
Yarmouth from 2014 is unexplained.

31 casco BAY estuary partnership

condition of the bay M. Toxics

NS&T 85th Percentile

Low and Decreasing Contaminant Levels in Casco Bay Blue Mussels Sum of 40 PAHs (ng/g) National
PAHs (ng/g)
Brunswick 1000

Freeport Mare Brook Contaminants in the ocean can pose human East End
Mill Creek
health risks if they find their way into seafoodG.ulfwatch 85th Percentile Spring Point

Harpswell Maine’s Surface Water Ambient Toxics (SWAT) 1000

program collects data on persistent cont5a0m0 - East En
Navy Pier Mill Cr
Gulf of Maine Spring
inants in several marine species, including

Falmouth blue mussels. Mussels are filter feeders,3a00nd 500
Mill Creek can concentrate contaminants from their

East End surroundings. National and regional programs 2 010 2 012 2 015

Portland Spring Point have tracked contaminants in mussels and 300 Year

Mussel Sampling Locations oysters for many years. CBEP analyzed Casco

South Portland Bay mussel data in relation to Gulf of Maine
(Gulfwatch) and National (NOAA) benchmarks.
From 2010 to 2019, data on toxic contam- Benchm­ arks used here (85th percentiles) 2 010 2 012 2 015
show levels exceeded by 15% of observations
inantsCape in mussels were collected from from regional and national studies. Year

Elizabeth

five locations in Casco Bay. Data has PAHs in blue mussels from all three long-term
monitoring sites have declined over the past
been collected multiple times since 2006 15 years. PCBs (not shown) have shown no
significant trends.
at Mill Creek, East End, and Spring Point.

Aluminum Arsenic Cadmium Chromium
Copper
500 Nickel 20 Aluminum 5 Arsenic 5 Chr
300 3 3 Cadmium
10
PAHs PCBs 100 8 500 20Aluminum 5 Arsenic 5Cadmium
20 1 3 3
National National Concentration (mg/g) 100 1000 300 500 1 5
100 30 500 3 1
Concentration (ng/g) 10 300 100 Iron 300 10 Lead 10 0.3 1 Mercury
Concentration (mg/g) 30 8 8 Lead 1 M
Navy Pier1000 5 10 Concentration (mg/g) 100 0.3 Lead
Mare BrookGulf of Maine 3 5 Copper 101000 Iron 0.230 Iron 30 0.2
Mill Creek 1 3 1000 10 10
Gulf of Maine 100 Copper Zinc 3 0.1
East End 30 500 0.1 3
Spring Point 30 100 3 500 300

300 10 30 300 Silver
Selenium 10

10 Nickel 1.00 Selenium 101031000001..0000.31000SeleniumSilver
Nickel
5 0.30 10 1000 Silver
3 0.510
100 0.03 3 5 1.00 300
0.30
1 0.10 100
3 5 0.03
Navy Pier Navy Pier Navy Pier
Mare Brook Mare Brook Mare Brook
Mill Creek
Mill Creek Navy Pier
East End East End Mill Creek
Spring Point Mare Brook
Spring Point
East End
Mill Creek
SprEianstg EPnoidnt
Spring Point
Navy Pier

Navy Pier
Mare Brook

MillMNaCarrveeyeBkPireorok
EMaasrtMeilElBnrdCoroekek
SpringMilPlEoiaCsrntteeEknd
SprEianstg EPnoidnt
Spring Point
Navy Pier
MareNBaNrvaoyvoykPiePirer
MiMllMaraCerreeBerBkorookok
EasMitlMlilElCnrdCereekek
Spring Point

EaEsatstEnEdnd
SSprpiringngPoPionitnt
Navy Pier
Mare Brook
MillNCarveyekPier
Mare Brook
1 3 0.03

PAHs in Casco Bay mussels near Portland are elevated Most metals in Casco Bay mussel tissue are well below benchmarks, Benchmarks:
compared to regional, but not national benchmarks. PCBs
are consistently below benchmarks. Published benchmarks with only lead and chromium showing fGreuqlf uoef Mntailneevels abNoatvieontahlGeulf of Maine National
compare the sum of a subset of PAHs and PCBs to levels of
similar totals from national and regional samples. Health- national benchmark. Most metals show scattered values above Gulf of Maine Nationa
based comparison levels are not available for PAHs. DEP
reports that levels of PCBs were below health action levels. regional benchmarks, with only nickel frequently above regional but
Recent data on pesticides and dioxins are unavailable.
not national benchmarks. Lead and mercury are highest near Portland, while selenium

is highest at Navy Pier and Mare Brook. Few metals show clear long-term trends, but

arsenic is increasing, while iron is decreasing Bay-wide, and chromium is decreasing at

East End and Spring Point (data not shown).

successes & challenges

▶ Concentrations of most toxic chemicals that have been studied in Casco Bay are below established levels of concern.
Exceptions tend to occur principally, but not exclusively, in our more urban waters. Most persistent contaminants are less
abundant today than in prior decades.

▶ Many persistent toxic chemicals, like PCBs and certain pesticides, were phased out in the late 20th century. Those
policies led to reductions in concentrations in the Bay. Reductions of other toxic chemicals may reflect better stormwater
management or reductions in tailpipe emissions from more fuel efficient, cleaner automobiles.

▶ Mercury still occurs at levels of potential concern for marine organisms in sediments across much of the Bay. A primary
source of mercury entering the Bay is atmospheric deposition, associated with discharges from power plants to our
west. Conditions may improve as coal-fired power plants are retired and replaced by natural gas and renewables.

▶ Historically, data collection on toxic contaminants in the marine environment has focused on persistent compounds
which were identified as problematic in the 1960s and 1970s. Data on modern contaminants of concern, from flame
retardants to microplastics, pharmaceuticals to personal care products, remains scarce.

STATE OF casco BAY 32


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