Regional assessment of status against human health thresholds in PAH concentrations in biota

Overview

This document provides additional regional assessments of the status of PAH concentrations in biota based on human health rather than environmental thresholds. The regional assessments are part of the 2020 assessment of CSEMP data and concern the PAHs BAP and FLU which are compared against the Quality Standard human health (QShh). Methodological details are only described briefly: further information can be found in the resource biota_regional_assessment_pahs.html.

Summary of individual time series results

This section summarises the individual time series assessments of trend and status for each PAH. This is the only place where trends are presented as the focus of this document is on status relative to the QShh.

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

• green: the mean concentration is significantly (p < 0.05) below the QShh
• red: the mean concentration is not signficantly below the QShh

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 second 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 green or red status in each biogeographic region and MS sub-region
• the same information presented as proportions

BAP

FLU

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	BAP	FLU	total
Greater North Sea	Northern North Sea	upward trend	0	1	1
		no trend	0	5	5
		downward trend	2	3	5
	total	upward trend	0	1	1
		no trend	0	5	5
		downward trend	2	3	5
Celtic Seas	Scottish Continental Shelf	upward trend	0	2	2
		no trend	0	2	2
		downward trend	0	1	1
	Minches & W Scotland	upward trend	0	1	1
		no trend	0	4	4
		downward trend	1	0	1
	Irish Sea	upward trend	0	0	0
		no trend	3	10	13
		downward trend	1	1	2
	total	upward trend	0	3	3
		no trend	3	16	19
		downward trend	2	2	4

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	BAP	FLU	total
Greater North Sea	Northern North Sea	upward trend	0	11	9
		no trend	0	56	46
		downward trend	100	33	45
	total	upward trend	0	11	9
		no trend	0	56	46
		downward trend	100	33	45
Celtic Seas	Scottish Continental Shelf	upward trend		40	40
		no trend		40	40
		downward trend		20	20
	Minches & W Scotland	upward trend	0	20	16
		no trend	0	80	67
		downward trend	100	0	17
	Irish Sea	upward trend	0	0	0
		no trend	75	91	87
		downward trend	25	9	13
	total	upward trend	0	14	12
		no trend	60	76	73
		downward trend	40	10	15

Status summary (numbers)

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

MS sub-region	biogeographic region	status	BAP	FLU	total
Greater North Sea	Northern North Sea	green	4	8	12
		red	3	1	4
	Southern North Sea	green	0	1	1
		red	0	0	0
	E Channel	green	1	1	2
		red	0	0	0
	total	green	5	10	15
		red	3	1	4
Celtic Seas	Scottish Continental Shelf	green	1	5	6
		red	0	0	0
	Minches & W Scotland	green	2	6	8
		red	0	0	0
	Irish Sea	green	13	18	31
		red	1	0	1
	total	green	16	29	45
		red	1	0	1

Status summary (proportions)

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

MS sub-region	biogeographic region	status	BAP	FLU	total
Greater North Sea	Northern North Sea	green	57	89	75
		red	43	11	25
	Southern North Sea	green		100	100
		red		0	0
	E Channel	green	100	100	100
		red	0	0	0
	total	green	62	91	79
		red	38	9	21
Celtic Seas	Scottish Continental Shelf	green	100	100	100
		red	0	0	0
	Minches & W Scotland	green	100	100	100
		red	0	0	0
	Irish Sea	green	93	100	97
		red	7	0	3
	total	green	94	100	98
		red	6	0	2

Regional assessment - methods

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 QShh. The regional status for each PAH is then estimated by fitting the following linear mixed model by restricted maximum likelihood:

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

Note that the fixed effects model differs from that used in the regional status assessment against environmental thresholds. Here there are only two PAHs and a separate regional trend is fitted for each. In the assessment against environmental thresholds there are ten PAHs. These are regarded as random effects and a common regional status is estimated averaged across PAHs.

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.

The meta-analysis is restricted to regions and PAH combinations with at least three status stations with good geographic spread.

The results of the status regional assessments are back-transformed for presentation. The estimated regional status is then interpreted as the ratio of the mean regional concentration to the assessment concentration. For example, 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 status assessments The following regions have an insufficient number or time series or spread of stations and are excluded from the regional assessment: E Channel, Northern North Sea, and Scottish Continental Shelf. `

Regional status compared to the Quality Standard human health (QShh)

The first 3 tabs show:

• 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:

• green: the mean concentration is significantly (p < 0.05) below the QShh
• red: the mean concentration is not significantly below the QShh

The final tab shows the estimates of the regional status by PAH.

Regional status by PAH

Regional status by region

Individual time series

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

biogeographic region	PAH	status	se	upper	concentration	conc upper
Minches & W Scotland	BAP	-2.77	0.36	-2.18	0.06	0.11
	FLU	-2.20	0.24	-1.80	0.11	0.17
Irish Sea	BAP	-1.55	0.16	-1.29	0.21	0.28
	FLU	-1.60	0.15	-1.35	0.20	0.26