Regional assessment of status and trends in PAH concentrations in biota

Overview

The 2020 assessment of CSEMP data describes the status and trends of contaminant concentrations in biota and sediment at monitoring stations around the UK. Assessments are made for a large number of time series, each of a single contaminant in a single species and tissue (for biota) at a single monitoring station. This document is one of a series that synthesises the results of the individual time series to assess status and trends at the biogeographic regional level. In particular, it considers PAH concentrations in biota, where the PAHs are NAP, ACNLE, ACNE, FLE, PA, ANT, DBT, FLU, PYR, BAA, CHR, BAP, BEP, BBKF, DBAHA, PER, BGHIP, ICDP.

The regional assessment only considers coastal and offshore stations and excludes estuarine stations. The results are therefore based on the monitoring data collected within the waters assessed under the UK Marine Strategy (MS). For simplicity, the term ‘region’ is used throughout to describe biogeographic regions. MS sub-regions are always referred to as such.

The regional status assessments presented in this document are based on environmental thresholds. Regional status assessments based on human health thresholds can be found in the resource biota_regional_assessment_pahs_health.html.

The following sections:

• summarise the individual time series results
• describe the methods used to combine the individual time series results to estimate regional status and trends
• present the estimates of regional trends
• present the estimates of regional status

Summary of individual time series results

A time series of PAH concentrations is assessed for status if:

• there is at least one year with data in the period 2014 to 2019
• there are at least three years of data over the whole time series
• a parametric model can be fitted to the data and used to estimate the mean concentration in the final monitoring year (or, occasionally, if a non-parametric test of status is applied)

The conditions are more stringent for trends. Specifically, a time series is assessed for trends if:

• there is at least one year with data in the period 2014 to 2019
• there are at least five years of data over the whole time series
• a parametric model can be fitted to the data and used to estimate the trend in mean concentration

Note that all trend assessments for individual time series and most status assessments are based on the fit of a parametric model. This is important because only the parametric results are passed into the regional assessments in the following sections. 13 of the 432 PAH time series were assessed for status using a non-parametric test.

The first tab below shows all the monitoring stations where there are individual time series assessments of trend or status for PAHs. The purple circles are stations where there is a trend assessment for at least one PAH, and the light blue cirles are stations where there are only status assessments. The areas delineated by the thinner black lines are the biogeographic regions; those delineated by the thicker black lines are the MS sub-regions.

The next set of tabs show the trend and status assessments for each PAH in turn. The colours have the following meaning:

• blue: the mean concentration is significantly (p < 0.05) below the Background Assessment Concentration (BAC)
• green: the mean concentration is significantly (p < 0.05) below the Environmental Assessment Criterion (EAC)
• orange: there is no EAC and the mean concentration is not significantly below the BAC
• red: the mean concentration is not signficantly below the EAC
• black: there are no assessment criteria available

And the shapes have the following meaning:

• downward triangle: the mean concentration is significantly decreasing (p < 0.05)
• circle: there is no significant change in mean concentration (p > 0.05) or there are too few years to test for trends
• upward triangle: the mean concentration is significantly increasing (p < 0.05)

The final set of tabs give:

• the number of time series with upwards, downwards or no trend in each biogeographic region and MS sub-region
• the same information presented as proportions
• the number of time series with blue, green, orange or red status in each biogeographic region and MS sub-region
• the same information presented as proportions

Note that only ten of the PAHs have assessment criteria: NAP, PA, ANT, FLU, PYR, BAA, CHR, BAP, BGHIP, ICDP. Of these, NAP and ANT only have an EAC and CHR and ICDP only have a BAC.

Stations

NAP

ACNLE

ACNE

FLE

PA

ANT

DBT

FLU

PYR

BAA

CHR

BAP

BEP

BBKF

DBAHA

PER

BGHIP

ICDP

Trend summary (numbers)

Number of time series with upwards, downwards or no trend by biogeographic region and MS sub-region

MS sub-region	biogeographic region	status	NAP	ACNLE	ACNE	FLE	PA	ANT	DBT	FLU	PYR	BAA	CHR	BAP	BEP	BBKF	PER	BGHIP	ICDP	total
Greater North Sea	Northern North Sea	upward trend	0	0	1	0	0	0	0	1	0	0	0	0	0	0	0	0	0	2
		no trend	7	5	4	3	7	5	0	5	5	2	7	0	3	0	0	2	3	58
		downward trend	1	0	0	1	2	2	0	3	4	6	1	2	4	0	0	5	1	32
	Southern North Sea	upward trend	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
		no trend	0	0	0	0	1	0	0	0	0	0	0	0	0	0	0	0	0	1
		downward trend	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	total	upward trend	0	0	1	0	0	0	0	1	0	0	0	0	0	0	0	0	0	2
		no trend	7	5	4	3	8	5	0	5	5	2	7	0	3	0	0	2	3	59
		downward trend	1	0	0	1	2	2	0	3	4	6	1	2	4	0	0	5	1	32
Celtic Seas	Scottish Continental Shelf	upward trend	0	0	0	0	0	0	0	2	1	0	0	0	0	0	0	0	0	3
		no trend	2	0	1	0	4	1	0	2	4	1	3	0	0	0	0	1	0	19
		downward trend	2	0	0	0	1	0	0	1	0	0	0	0	0	0	0	0	0	4
	Minches & W Scotland	upward trend	0	0	1	0	1	0	0	1	0	0	0	0	0	0	0	0	0	3
		no trend	4	0	0	1	3	0	0	4	5	1	3	0	1	1	0	1	1	25
		downward trend	0	0	0	0	0	0	0	0	0	0	1	1	0	0	1	0	0	3
	Irish Sea	upward trend	1	0	0	0	2	0	0	0	0	0	0	0	0	0	0	0	0	3
		no trend	4	0	1	1	7	7	1	10	9	4	6	3	1	0	1	4	5	64
		downward trend	1	0	0	0	2	0	0	1	2	3	1	1	0	0	0	4	2	17
	total	upward trend	1	0	1	0	3	0	0	3	1	0	0	0	0	0	0	0	0	9
		no trend	10	0	2	2	14	8	1	16	18	6	12	3	2	1	1	6	6	108
		downward trend	3	0	0	0	3	0	0	2	2	3	2	2	0	0	1	4	2	24

Trend summary (proportions)

Proportion of time series with upwards, downwards or no trend by biogeographic region and MS sub-region

MS sub-region	biogeographic region	status	NAP	ACNLE	ACNE	FLE	PA	ANT	DBT	FLU	PYR	BAA	CHR	BAP	BEP	BBKF	PER	BGHIP	ICDP	total
Greater North Sea	Northern North Sea	upward trend	0	0	20	0	0	0		11	0	0	0	0	0			0	0	2
		no trend	88	100	80	75	78	71		56	56	25	88	0	43			29	75	63
		downward trend	12	0	0	25	22	29		33	44	75	12	100	57			71	25	35
	Southern North Sea	upward trend					0													0
		no trend					100													100
		downward trend					0													0
	total	upward trend	0	0	20	0	0	0		11	0	0	0	0	0			0	0	2
		no trend	88	100	80	75	80	71		56	56	25	88	0	43			29	75	64
		downward trend	12	0	0	25	20	29		33	44	75	12	100	57			71	25	34
Celtic Seas	Scottish Continental Shelf	upward trend	0		0		0	0		40	20	0	0					0		12
		no trend	50		100		80	100		40	80	100	100					100		73
		downward trend	50		0		20	0		20	0	0	0					0		15
	Minches & W Scotland	upward trend	0		100	0	25			20	0	0	0	0	0	0	0	0	0	10
		no trend	100		0	100	75			80	100	100	75	0	100	100	0	100	100	80
		downward trend	0		0	0	0			0	0	0	25	100	0	0	100	0	0	10
	Irish Sea	upward trend	16		0	0	18	0	0	0	0	0	0	0	0		0	0	0	4
		no trend	67		100	100	64	100	100	91	82	57	86	75	100		100	50	71	76
		downward trend	17		0	0	18	0	0	9	18	43	14	25	0		0	50	29	20
	total	upward trend	7		33	0	15	0	0	14	5	0	0	0	0	0	0	0	0	6
		no trend	72		67	100	70	100	100	76	86	67	86	60	100	100	50	60	75	77
		downward trend	21		0	0	15	0	0	10	9	33	14	40	0	0	50	40	25	17

Status summary (numbers)

Number of time series with each status by biogeographic region and MS sub-region

MS sub-region	biogeographic region	status	NAP	PA	ANT	FLU	PYR	BAA	CHR	BAP	BGHIP	ICDP	total
Greater North Sea	Northern North Sea	blue	0	0	0	0	0	0	0	0	0	0	0
		green	8	9	9	7	7	7	0	6	8	0	61
		orange	0	0	0	0	0	0	9	0	0	8	17
		red	1	0	0	2	2	1	0	1	0	0	7
	Southern North Sea	blue	0	0	0	0	0	0	1	0	0	0	1
		green	0	1	1	1	0	1	0	0	1	0	5
		orange	0	0	0	0	0	0	0	0	0	1	1
		red	0	0	0	0	0	0	0	0	0	0	0
	E Channel	blue	0	0	0	0	0	0	0	0	0	0	0
		green	0	1	1	1	1	1	0	1	1	0	7
		orange	0	0	0	0	0	0	1	0	0	0	1
		red	1	0	0	0	0	0	0	0	0	0	1
	total	blue	0	0	0	0	0	0	1	0	0	0	1
		green	8	11	11	9	8	9	0	7	10	0	73
		orange	0	0	0	0	0	0	10	0	0	9	19
		red	2	0	0	2	2	1	0	1	0	0	8
Celtic Seas	Scottish Continental Shelf	blue	0	1	0	1	0	0	0	0	0	0	2
		green	5	4	5	4	5	2	0	1	2	0	28
		orange	0	0	0	0	0	0	5	0	0	2	7
		red	0	0	0	0	0	0	0	0	0	0	0
	Minches & W Scotland	blue	0	1	0	1	1	1	2	1	0	1	8
		green	4	5	5	4	4	1	0	1	2	0	26
		orange	0	0	0	0	0	0	4	0	0	1	5
		red	1	0	0	1	1	0	0	0	0	0	3
	Irish Sea	blue	0	0	0	0	0	0	0	0	0	0	0
		green	14	18	17	15	12	12	0	14	14	0	116
		orange	0	0	0	0	0	0	17	0	0	14	31
		red	2	0	0	3	5	2	0	0	0	0	12
	total	blue	0	2	0	2	1	1	2	1	0	1	10
		green	23	27	27	23	21	15	0	16	18	0	170
		orange	0	0	0	0	0	0	26	0	0	17	43
		red	3	0	0	4	6	2	0	0	0	0	15

Status summary (proportions)

Proportion of time series with each status by biogeographic region and MS sub-region

MS sub-region	biogeographic region	status	NAP	PA	ANT	FLU	PYR	BAA	CHR	BAP	BGHIP	ICDP	total
Greater North Sea	Northern North Sea	blue	0	0	0	0	0	0	0	0	0	0	0
		green	89	100	100	78	78	88	0	86	100	0	72
		orange	0	0	0	0	0	0	100	0	0	100	20
		red	11	0	0	22	22	12	0	14	0	0	8
	Southern North Sea	blue		0	0	0		0	100		0	0	14
		green		100	100	100		100	0		100	0	72
		orange		0	0	0		0	0		0	100	14
		red		0	0	0		0	0		0	0	0
	E Channel	blue	0	0	0	0	0	0	0	0	0		0
		green	0	100	100	100	100	100	0	100	100		78
		orange	0	0	0	0	0	0	100	0	0		11
		red	100	0	0	0	0	0	0	0	0		11
	total	blue	0	0	0	0	0	0	9	0	0	0	1
		green	80	100	100	82	80	90	0	88	100	0	72
		orange	0	0	0	0	0	0	91	0	0	100	19
		red	20	0	0	18	20	10	0	12	0	0	8
Celtic Seas	Scottish Continental Shelf	blue	0	20	0	20	0	0	0	0	0	0	5
		green	100	80	100	80	100	100	0	100	100	0	76
		orange	0	0	0	0	0	0	100	0	0	100	19
		red	0	0	0	0	0	0	0	0	0	0	0
	Minches & W Scotland	blue	0	17	0	16	16	50	33	50	0	50	19
		green	80	83	100	67	67	50	0	50	100	0	62
		orange	0	0	0	0	0	0	67	0	0	50	12
		red	20	0	0	17	17	0	0	0	0	0	7
	Irish Sea	blue	0	0	0	0	0	0	0	0	0	0	0
		green	88	100	100	83	71	86	0	100	100	0	73
		orange	0	0	0	0	0	0	100	0	0	100	19
		red	12	0	0	17	29	14	0	0	0	0	8
	total	blue	0	7	0	7	4	6	7	6	0	6	4
		green	88	93	100	79	75	83	0	94	100	0	72
		orange	0	0	0	0	0	0	93	0	0	94	18
		red	12	0	0	14	21	11	0	0	0	0	6

Regional assessment - methods

Tabulating the number of time series with each status category by region provides a quick summary of the individual time series results. However, it does not provide an objective regional assessment of status. Similarly, tabulating the number of time series with an upward or downward trend does not provide an objective regional assessment of trend. This section describes how the individual time series results can by synthesised in a meta-analysis to assess both status and trend at the regional level.

Trends

For a regional trend assessment, the trend in each time series is summarised by the estimated change in log concentration over the last twenty years (or shorter if the time series doesn’t extend that far back). Regional trends are then estimated by fitting the following linear mixed model by restricted maximum likelihood:

• response: trend (yearly change in log concentration)
• fixed model: region
• random model: PAH + region.PAH + station + trend estimation variation + residual variation

The fixed model means that a trend is estimated for each region. Trends in the different PAHs are assumed to be broadly similar, because inputs and control measures are likely to affect all PAHs in a similar way. Each regional trend can thus be interpreted as the common trend in PAH concentrations in that region (i.e. the trend averaged across all PAHs).

The random model has five terms:

• PAH allows for variation in trend between PAHs common to all regions
• region.PAH allows for additional variation in trend between PAHs within regions
• station allows for variation in trend between stations common to all PAHs
• trend estimation variation is the variance of the trend estimates from the individual time series analysis, assumed known and fixed
• residual variation is the variation that cannot be explained by any of the fixed effects or the other random effects

The meta-analysis is restricted to time series from monitoring stations that are classified as ‘representative’ or ‘baseline’ (near pristine conditions or only subject to very diffuse inputs). ‘Impacted’ stations (those close to a point source) are omitted because trends there will likely reflect changes due to the point source and will be ‘unrepresentative’ at the regional level.

The meta-analysis is further restricted to:

• regions with at least three trend stations with good geographic spread. Three stations is considered the minimum required to provide some sort of evidence base at the regional level
• PAHs with trend information for at least three stations (over all regions): PAHs are treated as random effects in the meta-anlaysis, so information about trends in one PAH can be ‘borrowed’ from the trend information in the other PAHs

Status

For a regional status assessment, the status of each time series is summarised by the difference between the estimated mean log concentration in the final monitoring year and the log assessment concentration. This ensures that status is always measured on the same scale, even though the assessment concentration might vary between PAHs and species. Essentially the same linear mixed model as for trends is then fitted:

• response: status (mean log concentration - log assessment concentration)
• fixed model: region
• random model: PAH + region.PAH + station + status estimation variation + residual variation

where status estimation variation is the variation in the status estimates from the individual time series analysis, assumed known and fixed.

There are no restrictions on the time series used in the status meta-analysis based on the classification of the monitoring station; time series from baseline, representative and impacted stations are all included. However, the few time series with a non-parametric assessment of status must be excluded, because there is no summary measure of status to use in the mixed model.

Again, the meta-analysis is restricted to regions with at least three status stations with good geographic spread and to PAHs with status information for at least three stations (over all regions).

Presentation

The results of both the trend and status regional assessments are back-transformed for presentation. The estimated regional trend is then interpreted as the percentage yearly change in concentration and the estimated regional status as the ratio of the mean regional concentration to the assessment concentration. To illustrate the latter, a value of 1 indicates that the mean regional concentration is equal to the assessment concentration; a value of 0.5 indicates that it is half the assessment concentration, and a value of 2 indicates that it is twice the assessment concentration.

Regional assessment - availability of time series

This section provides more detail on the number and geographic spread of the time series available for the meta-analyses. The map shows the stations with parametric trend and status assessments having excluded trend assessments at baseline and impacted stations. The purple circles are stations where there is a trend assessment for at least one PAH, and the light blue cirles are stations where there are only status assessments.

The following regions have an insufficient number or time series or spread of stations and are excluded from the regional assessment:

• trend: Northern North Sea, Scottish Continental Shelf, Southern North Sea
• status: E Channel, Northern North Sea, Scottish Continental Shelf, Southern North Sea

Regional trends

The first 4 tabs show:

• Regional trends: estimates of the regional trend (averaged over PAHs) with pointwise 95% confidence intervals
• Regional trends by PAH: regional trend estimates for each PAH with pointwise 95% confidence intervals plotted by PAH
• Regional trends by region: regional trend estimates for each PAH with pointwise 95% confidence intervals plotted by region
• Individual time series: the trend estimates from the individual time series on which the regional assessment is based. The estimates for regions with insufficient geographic spread (and excluded from the meta-analysis) are also shown.

The symbols in all these plots have the following interpretation:

• downward triangle: the mean concentration is significantly decreasing (p < 0.05)
• circle: there is no significant change in mean concentration (p > 0.05)
• upward triangle: the mean concentration is significantly increasing (p < 0.05)

The final 2 tabs show the estimates of the regional trend (averaged over PAHs) and the regional trend by PAH

Regional trends

Regional trends by PAH

Regional trends by region

Individual time series

Estimates by region

This table shows the estimates of the regional trend:

• trend: the estimated mean yearly change in log concentration across the region (multiplied by 100 for presentation)
• se: the corresponding standard error
• lower, upper: the corresponding pointwise 95% confidence limits
• % yearly change: the estimated mean % yearly change in concentration across the region
• %yc lower, %yc upper: the corresponding pointwise 95% confidence limits

biogeographic region	trend	se	lower	upper	% yearly change	%yc lower	%yc upper
Minches & W Scotland	0.87	3.30	-5.60	7.33	0.87	-5.44	7.61
Irish Sea	-5.11	2.19	-9.40	-0.81	-4.98	-8.97	-0.81

Estimates by region and PAH

This table shows the estimates of the regional trend by determinand:

• trend: the estimated mean yearly change in log concentration across the region (multiplied by 100 for presentation)
• se: the corresponding standard error
• lower, upper: the corresponding pointwise 95% confidence limits
• % yearly change: the estimated mean % yearly change in concentration across the region
• %yc lower, %yc upper: the corresponding pointwise 95% confidence limits

biogeographic region	PAH	trend	se	lower	upper	% yearly change	%yc lower	%yc upper
Minches & W Scotland	NAP	-1.59	3.82	-9.08	5.90	-1.58	-8.68	6.08
	PA	5.02	3.46	-1.76	11.79	5.14	-1.74	12.51
	FLU	2.52	3.27	-3.89	8.93	2.55	-3.81	9.34
	PYR	0.74	3.31	-5.75	7.24	0.75	-5.59	7.51
	BAA	-0.05	3.62	-7.14	7.04	-0.05	-6.89	7.30
	CHR	-0.34	3.48	-7.17	6.48	-0.34	-6.92	6.70
	BAP	-1.02	3.75	-8.37	6.34	-1.01	-8.03	6.55
	BGHIP	0.21	3.52	-6.68	7.11	0.21	-6.46	7.37
	ICDP	1.03	3.61	-6.05	8.11	1.03	-5.87	8.45
Irish Sea	NAP	-7.56	2.95	-13.35	-1.78	-7.29	-12.50	-1.77
	PA	-0.96	2.44	-5.75	3.83	-0.95	-5.59	3.91
	ANT	-3.84	3.00	-9.72	2.05	-3.76	-9.27	2.08
	FLU	-3.45	2.28	-7.93	1.02	-3.39	-7.62	1.03
	PYR	-5.23	2.33	-9.79	-0.67	-5.09	-9.32	-0.67
	BAA	-6.02	2.60	-11.12	-0.93	-5.85	-10.52	-0.93
	CHR	-6.32	2.49	-11.19	-1.44	-6.12	-10.59	-1.43
	BAP	-6.99	2.78	-12.44	-1.54	-6.75	-11.70	-1.53
	BGHIP	-5.76	2.44	-10.54	-0.98	-5.60	-10.01	-0.97
	ICDP	-4.94	2.59	-10.02	0.13	-4.82	-9.53	0.13

Regional status compared to the Environmental Assessment Criterion (EAC)

The first 4 tabs show:

• Regional status: estimates of the regional status (averaged over PAHs) with pointwise upper one-sided 95% confidence intervals
• Regional status by PAH: regional status estimates for each PAH with pointwise upper one-sided 95% confidence intervals plotted by PAH
• Regional status by region: regional status estimates for each PAH with pointwise upper one-sided 95% confidence intervals plotted by region
• Individual time series: the status estimates from the individual time series on which the regional assessment is based. The estimates for regions with insufficient geographic spread (and excluded from the meta-analysis) are also shown.

The symbols in all the plots have the following interpretation:

• blue: the mean concentration is significantly (p < 0.05) below the Background Assessment Concentration (BAC)
• green: the mean concentration is significantly (p < 0.05) below the EAC
• red: the mean concentration is not significantly below the EAC

Note that to see why some points might be coloured blue, it is necessary to look ahead to the next section, where status is compared to the BAC. Unfortunately, it isn’t easy to present the assessment of status relative to the EAC with the assessment of status relative to the BAC because the ratio of the BAC to the EAC can vary between PAHs and species.

The final 2 tabs show the estimates of the regional status (averaged over PAHs) and the regional status trend by PAH

Regional status

Regional status by PAH

Regional status by region

Individual time series

Estimates by region

This table shows the estimates of the regional status:

• status: the estimated mean log concentration minus the log EAC
• se: the corresponding standard error
• upper: the corresponding pointwise upper one-sided 95% confidence limit
• concentration: the estimated mean concentration relative to the EAC
• conc upper: the corresponding pointwise upper one-sided 95% confidence limit

biogeographic region	status	se	upper	concentration	conc upper
Minches & W Scotland	-3.61	0.58	-2.66	0.03	0.07
Irish Sea	-2.99	0.54	-2.09	0.05	0.12

Estimates by region and PAH

This table shows the estimates of the regional trend by determinand:

• status: the estimated mean log concentration minus the log EAC
• se: the corresponding standard error
• upper: the corresponding pointwise upper one-sided 95% confidence limit
• concentration: the estimated mean concentration relative to the EAC
• conc upper: the corresponding pointwise upper one-sided 95% confidence limit

biogeographic region	PAH	status	se	upper	concentration	conc upper
Minches & W Scotland	NAP	-4.19	0.33	-3.64	0.02	0.03
	PA	-4.50	0.27	-4.06	0.01	0.02
	ANT	-5.29	0.31	-4.79	0.01	0.01
	FLU	-1.72	0.25	-1.31	0.18	0.27
	PYR	-1.88	0.25	-1.46	0.15	0.23
	BAA	-2.73	0.32	-2.21	0.06	0.11
	CHR
	BAP	-5.43	0.33	-4.88	0.00	0.01
	BGHIP	-3.12	0.30	-2.63	0.04	0.07
	ICDP
Irish Sea	NAP	-4.38	0.21	-4.04	0.01	0.02
	PA	-4.25	0.16	-3.99	0.01	0.02
	ANT	-4.17	0.16	-3.90	0.02	0.02
	FLU	-1.12	0.15	-0.87	0.33	0.42
	PYR	-1.05	0.15	-0.80	0.35	0.45
	BAA	-1.87	0.16	-1.60	0.15	0.20
	CHR
	BAP	-4.52	0.16	-4.26	0.01	0.01
	BGHIP	-2.55	0.16	-2.28	0.08	0.10
	ICDP

Regional status compared to the Background Assessment Concentration (BAC)

The first 4 tabs show:

• Regional status: estimates of the regional status (averaged over PAHs) with pointwise upper one-sided 95% confidence intervals
• Regional status by PAH: regional status estimates for each PAH with pointwise upper one-sided 95% confidence intervals plotted by PAH
• Regional status by region: regional status estimates for each PAH with pointwise upper one-sided 95% confidence intervals plotted by region
• Individual time series: the status estimates from the individual time series on which the regional assessment is based. The estimates for regions with insufficient geographic spread (and excluded from the meta-analysis) are also shown.

The symbols in all the plots have the following interpretation:

• blue: the mean concentration is significantly (p < 0.05) below the BAC
• green: the mean concentration is significantly (p < 0.05) below the Environmental Assessment Criterion (EAC)
• orange: there is no EAC and the mean concentration is not significantly below the BAC
• red: the mean concentration is not significantly below the EAC

The final 2 tabs show the estimates of the regional status (averaged over PAHs) and the regional status trend by PAH

Regional status

Regional status by PAH

Regional status by region

Individual time series

Estimates by region

This table shows the estimates of the regional status:

• status: the estimated mean log concentration minus the log BAC
• se: the corresponding standard error
• upper: the corresponding pointwise upper one-sided 95% confidence limit
• concentration: the estimated mean concentration relative to the BAC
• conc upper: the corresponding pointwise upper one-sided 95% confidence limit

biogeographic region	status	se	upper	concentration	conc upper
Minches & W Scotland	0.39	0.26	0.82	1.47	2.27
Irish Sea	1.16	0.17	1.44	3.19	4.24

Estimates by region and PAH

This table shows the estimates of the regional trend by determinand:

• status: the estimated mean log concentration minus the log BAC
• se: the corresponding standard error
• upper: the corresponding pointwise upper one-sided 95% confidence limit
• concentration: the estimated mean concentration relative to the BAC
• conc upper: the corresponding pointwise upper one-sided 95% confidence limit

biogeographic region	PAH	status	se	upper	concentration	conc upper
Minches & W Scotland	NAP
	PA	0.44	0.27	0.89	1.55	2.42
	ANT
	FLU	0.46	0.26	0.89	1.59	2.43
	PYR	0.51	0.26	0.94	1.66	2.55
	BAA	0.59	0.30	1.08	1.80	2.94
	CHR	-0.05	0.28	0.40	0.95	1.49
	BAP	0.51	0.30	1.01	1.66	2.74
	BGHIP	0.48	0.29	0.96	1.61	2.61
	ICDP	0.16	0.29	0.64	1.17	1.90
Irish Sea	NAP
	PA	0.86	0.16	1.13	2.37	3.10
	ANT
	FLU	1.10	0.16	1.36	3.01	3.92
	PYR	1.36	0.16	1.62	3.88	5.05
	BAA	1.56	0.17	1.84	4.77	6.28
	CHR	0.85	0.16	1.11	2.33	3.03
	BAP	1.51	0.16	1.78	4.51	5.90
	BGHIP	1.21	0.16	1.48	3.35	4.38
	ICDP	0.83	0.17	1.11	2.30	3.03

PAH profiles

The profile of concentrations across PAHs can sometimes be useful for examining sources, and for comparing concentrations across regions where assessment criteria are not available. Profiles were examined by fitting the following linear mixed model by restricted maximum likelihood:

• response: mean log concentration
• fixed model: region
• random model: PAH + region.PAH + station + estimation variation + residual variation

where, for each time series, the mean log concentration is the estimated mean log concentration in the final monitoring year and the estimation variance is the variance associated with this estimate.

The estimated PAH concentration profiles by region are shown below with pointwise 95% confidence limits. The units are ug/kg dw.